Germination behaviour of the seeds of seven New Zealand woody plant species

Transcription

1 New Zealand Jurnal f Btany ISSN: X (Print) (Online) Jurnal hmepage: Germinatin behaviur f the seeds f seven New Zealand wdy plant species C. J. Burrws T cite this article: C. J. Burrws (1996) Germinatin behaviur f the seeds f seven New Zealand wdy plant species, New Zealand Jurnal f Btany, 34:3, , DOI: 1.18/28825X T link t this article: Published nline: 31 Jan 212. Submit yur article t this jurnal Article views: 325 Citing articles: 9 View citing articles Full Terms & Cnditins f access and use can be fund at

2 New Zealand Jurnal f Btany, 1996, Vl. 34: X/96/ $2.5/ 9 The Ryal Sciety f New Zealand Germinatin behaviur f the seeds f seven New Zealand wdy plant species C. J. BURROWS Department f Plant and Micrbial Sciences University f Canterbury Private Bag 48 Christchurch, New Zealand Abstract Germinatin rates, percentage germinatin success, and phenmena related t germinatin delay were determined fr seeds frm freshly cllected fruit f Carpdetus serratus, Cprsma lucida, Pittsprum eugeniides, P. tenuiflium, Plagianthus regius, Pseudpanax arbreus, and P. crassiflius. The experimental treatments simulated natural cnditins that the seeds might experience after dispersal. The percentage germinatin success fr all species in well-lit cnditins was very high (94-1%). The lengths f time befre the start f germinatin and fr its cmpletin differ fr each species. The seeds f all species tested germinated within a year. Seeds f all species germinated in the dark, but usually germinatin rates were slw and percentage success was relatively lw. The same applied t seeds placed n sil. Seeds left in the pericarp tissues failed t germinate except fr Plagianthus, Pseudpanax crassiflius, and ne cllectin f Pittsprum eugeniides. The verall flexible germinatin behaviur accrds well with the versatile behaviur f these species as clnisers f pen r shrubby habitats, as well as their capacity fr inhabiting clsed frest cmmunities. Keywrds seeds; germinatin tests; simulating nature; germinatin delay; well spread germinatin B9549 Received 16 Octber 1995; accepted 7 June 1996 INTRODUCTION The research described here is part f a series f studies aimed at discvering the patterns f germinatin f seeds f wdy plant species frm New Zealand lwland frests under cnditins similar t thse that the seeds wuld experience in nature (cf. Burrws 1995a, 1995b). Germinatin rates, numbers f seeds which finally germinate, and aspects f the germinatin delay systems fr seeds cllected fresh frm the parent plants are investigated. Features cmmn t the species tested are relatively lng displays f mature fruit and, after seeds are dispersed, lng delays befre germinatin cmmences, r befre all seeds in a set germinate. Other wrkers have already published germinatin infrmatin fr sme f the species, e.g., Hrrell et al. (199), Bannister & Bridgman (1991) n Pseudpanax arbreus and P. crassiflius, Burrws (1993a) n all seven species, Bannister & Jamesn (1994) and Mre et al. (1994) n Pittsprum eugeniides and P. tenuiflium. Plant nmenclature fllws Allan (1961) and Cnnr & Edgar (1987). The individual disseminules f all species are referred t as seeds, althugh tw include maternal tissue, in the frm f the entire vary wall (Plagianthus), r as endcarp, the tugh inner part f the vary wall (Cprsma). The species tested Carpdetus serratus J.R.Frst. et G.Frst. (E scall ni aceae) An evergreen, single-, r multi-stemmed, straight r leaning tree up t 1 m tall. The juvenile frm is divaricate and has smaller leaves. The species ccurs widely in lwland t mntane frests, in the understrey, at frest margins, r frming small grves in regenerating frest r in frest gaps. The bisexual flwers are brne in small panicles, in axils f leaves, n shrt branchlets n the upper branches. The unripe fruit are capsule-like and five-celled. They ripen t dark purplish-black, sft and juicy berries cntaining many small seeds with axile placentatin.

3 356 New Zealand Jurnal f Btany, 1996, Vl. 34 Cprsma lucida J.R.Frst. et G.Frst. (Rubiaceae) An evergreen, diecius shrub, with leaning r fastigiate branches, up t 6 m tall. It is widespread in lwland t mntane frest as a minr cmpnent in the understrey, in gaps, a,; an epiphyte n ld trees, at frest margins, and in regenerating frest. Flwers f female plants ccur in paniculate clusters, n shrt shts in the axils f leaves, n uter branches. The fruit are tw-seeded range drupes with juicy pericarps. Each seed is enclsed by endcarp. Pittsprum eugeniides A.Cunn. (Pittspraceae) An evergreen, erect, single- r multi-stemmed tree, up t 12 m tall, widespread in lwland t mntane frest. It is diecius but may have sme flwers f either sex r perfect flwers in the same inflrescence. It may be a canpy species but therwise ccurs in gaps, at frest margins, r in regenerating frest, smetimes frming small grves. The umbellike inflrescences are brne terminally, at branch tips. The fruit are tugh, bivalved capsules, pening when ripe t reveal a papery endcarp enclsing black seeds cvered with sticky mucilage. Pittsprum tenuiflium Sl. & Gaert. (Pittspraceae) An evergreen, single- r multi-stemmed, erect r leaning tree up t abut 9 m tall, widespread in lwland t mntane frest. Cmmnly it ccurs in gaps, at frest margins, and in regenerating frest. The bisexual flwers are slitary r smetimes in small clusters, n shrt pedicels subtended by bracts, in the axils f leaves n uter branches. The fruit are tugh, tw- r three-valved capsules, pening t reveal black seeds cvered with sticky., yellwish mucilage. Plagianthus regius (Piteau) Hchr. (Malvaceae) A winter-deciduus, single-stemmed erect tree up t abut 15 m tall. The juvenile frm is divaricate, with smaller leaves. The species ccurs widely in lwland r lwer mntane frest, smetimes as an emergent, and at frest margins. It smetimes frms grves n river fldplains r in regenerating frest. The inflrescences are large cymse ]panicles bme in the axils f leaves n the uter branches. It is diecius but may have sme flwers f either sex r perfect flwers in the same inflresce, nce. Individual ripe fruit are dry, achene-like, and single-seeded r smetimes duble-seeded. Pseudpanax arbreus (Murray) Philipsn (Araliaceae) An evergreen single- r multi-stemmed tree with spreading branches, up t abut 9 m tall. It is widespread in lwland frests, especially in gaps, at margins, and in regenerating frest. The inflrescences are cmpund, many-flwered umbels, terminal n the branches. The plants are diecius but may have sme flwers f either sex r perfect flwers in the same inflrescence. The ripe fruit are flattened, smewhat fleshy and juicy, with a purplish black pericarp surrunding tw seeds. Pseudpanax crassiflius (Sl. ex A.Cunn.) C.Kch (Araliaceae) An evergreen single- r multi-stemmed, erect tree up t abut 12 m tall. The juveniles have distinctive, lng, deflexed leaves. The species is cmmn in lwland t mntane frests in the understrey, as a canpy tree, r in gaps, at :frest margins, r in regenerating frest. The bisexual flwers are brne in terminal cmpund umbels n branchlets. The five lcules f the smewhat juicy fruit each cntain ne seed. When mature they may be green, green bltched purplish-black, r cmpletely purplishblack with green flesh. Seed dispersal Dispersal f the dry Plagianthus regius fruit is ften by detachment f the whle infructescence which falls r is blwn away frm the tree. Single fruit are als detached and wind-carried. Birds frage in pen, dry capsules f the Pittsprum spp. and mucilagefree seeds are caught in seed traps distant frm the parent trees (Burrws 1994a). It is assumed that they have passed thrugh birds (which eat them apparently t btain nutriment frm the mucilage). The fruit f the remaining fur species are eaten and the seeds dispersed by birds. Silvereyes (Zsterps lateralis) were seen eating the seeds f Pittsprurn eugeniides and the fruit f Carpdetus, Cprsma, and the tw Pseudpanax species. Bellbirds (Anthrnis melanura) ate fruit f the last fur f these species; kereru (Hemiphaga nvae seelandiae) ate fruit f Cprsma and Pseudpanax crassiflius; blackbirds (Turdus merula) ate fruit f Carpdetus and Cprsma. MATERIALS AND METHODS Ripe fruit were cllected in natural frest areas and prcessed within a few days by the methds utlined

4 Burrws---Germinatin f seven wdy plant species 357 IJ:I ::: ::J ~ Table 1 Fruit and seed prperties. Cunts and measurements were dne n randm samples f freshly-cllected fruit and thrughly air-dried seeds frm the b.--.~ ~.'~ ~ m ~ ['-" d r~ e 2 ~ "~1~ ~. ~'~. ~.~.,..~ "~ ~~ cllectin lcalities; unless therwise indicated ten individuals were cunted and measured. The values are mean ± standard deviatins. N errr values are prvided fr the mean seed weights which were btained by weighing a given number f seeds. The seeds r fruit f Cprsma, Pseudpanax arbreus, and P. 8 ""~ ~~ ~.~~ ~:~ ~,.~ ~~ ~'-~ -.~ ~ crassiflius are flattened; the narrwest dimensin was nt measured. *Many fruit f sme plants have ne abrted seed. S a ::::s Cllectin date; N f fruit Ripe fruit Grid reference per length -, Taxn (NZMS 26); infruct- f main Ripe fruit N. f full Seed Seed width Mean seed '" Lcatin Altitude (m) escence axis (mm) diam. (mm) seeds per fruit length(mm) (mm) weight (g) <: n ~ ~ 9 ~ ~.~. ~g ::::s Carpdetus serratus 3 lun ± ± ± ± ± ± ~ ~" ~ ~ ~ t~ Pq! ~ ~ " E ~3 ~ r d d d Maruia Springs, M Buller 62 '< ' ;::.;... ::::s ' '" Cprsma lucida 15 Feb ± ±.8 6.1± ± ± Prt Hills, M western Banks Peninsula 47 Pittsprum eugeniides 31 Sep ± ±.5 5.8±.3 7.4±.8 2.9± ± Riccartn Bush, M (n == 5) Christchurch 9.5 Pittsprum tenuiflium 15 Mar ± ± ± ± ± Prt Hills, M western Banks Peninsula 42 Plagianthus regius 15 Feb ± ±.4 2.1±.1 See fruit dimensins H r'-: '; O~ ~ I -H -H -H -I--I -I.-I -I.-I -H -H H -H -H O~ ~,'~ ~ ~_~~ i E. 5 (") '" ~ -~'~~ Prt Hills, M (n == 5) western Banks Peninsula 318 Pseudpanax arbreus 15 Apr ± ±.4 5.4±.3 2* 3.97± ± Prt Hills, M (n == 2) western Banks Peninsula 38 Pseudpanax crassiflius 22 lun ± ±.3 5.5± ±.3 2.4± Prt Hills, M (n == 5) western Banks Peninsula 42

5 358 New Zealand Jumal f Btany, 1996, Vl. 34 "25- e- E.~2ww Fig. 1 Mean mnthly maximum and minimum temperatures fr the Canterbury Btanical Gardens site, central Christchurch (frm a data printut frm the New Zealand Meterlgical Service). ] I I I I I I I! I I I I I I I I I I I I I I I D JF MAMJ JASONDJFMAMJ J ASONDJ F I 1989 I 199 I by Burrws (1995a). Table 1 summarises data fr lcalities and fruit and seed characteristics. Mdular replicates f 25 seeds were used fr each test. The treatments were: standard (pericarps remved, seeds washed and maintained in petri dishes n filter paper in wet, well-lit cnditins, 4 replicates); dark (cnditins the same as the standard except that petri dishes were wrapped in aluminium fil and examined peridically in a darkxm under a Kdak phtgraphic "safelight", 2 replicates; sil (cnditins the same as the standard except that seeds were placed, partially-expsed, n mist sil, in small plastic trays, 2 replicates; in-fruit (cnditins the same as fr the standard except that pericarps were left arund the seeds, 2 replicates). Mucilage surrunding Pittsprum seeds was nt fully remved by the saking in water which all seeds received. At the beginning f the experiments, tetrazlium tests fr ptential germinability we, re perfrmed n 25 fresh seeds f each species. Sme supplementary experiments fr several f the species are nted later. These were carried ut in in similar cnditins t the main series, t check n particular pints and fill gaps in tlhe infrmatin. The experiments were maintained in an unheated, partially-shaded glasshuse, with autmatic watering, at the University f Canterbury Plant and Micrbial Sciences Department garden area, as described by Burrws (1995a). Temperatures were mnitred with a Casella mercury-in-steel thermgraph and maximum-minimum thermmeters. The temperatures clsely fllwed the recrd fr the New Zealand Meterlgical Service statin at the Christchurch Btanical Gardens (Fig. 1). The standard and in-fruit treatments were checked at abut weekly intervals, the sil treatment at perids frm a week t a mnth, and the dark treatment abut nce in tw mnths. The first signs f genninatin are: Carpdetus, Pittsprum eugeniides cracked cat; Cprsma split endcarp; Pittsprum tenuiflium cat sftened, bulging, cracked; Plagianthus darkened and cracked cat; Pseudpanax species cat split alng mid-line. Within-treatment variability f the final amunts f germinatin is relatively lw (Table 2). Graphical representatin f the results is cnsidered adequate. RESULTS Results frm the main (1989-9) series are summarised fr all species and treatments in Table 2 and als presented graphically (Fig. 2-8). The supplementary experiment results are summarised in Table 3. Each species behaved individualistically in respnse t the prevailing cnditins. The differing germinatin patterns prbably arise frm bth endgenus and exgenus factrs, as will be explained in the discussin. Tetrazlium tests fr Carpdetus, Cprsma, Pittsprum eugeniides, and Pseudpanax arbreus seeds indicated substantially lwer ptential germinability than was achieved in the standard treatment (Table 2). Fewer Pittsprum tenuiflium seeds in the riginal experiment germinated in the standard treatment than the tetrazlium test indicated was pssible; this may have been due t fungal attack n sme seeds. Cprsma Fruit f Cprsma may persist n the parent frm January t March, r smetimes later. Seeds were cllected in February 199. In the standard

6 Burrws---Germinatin f seven wdy plant species 359 t ~ =l :8 b 9 Er... p :::s >+, fjl <: :::s :8 p... '<: ' S"... :::s fjl ' ;;;. n fjl VJ Vl '- Sil TT % x s % viable.,,., 14.5± ± tr ~ tr tr ± ± ± t ~ t"- ~ ~ 6,4 22.5± t-.--.,5 +1 N. germinated per treatment Dark In-fruit % x s % x s % ± ±.5 95 c'q ~ ~ r t'--- '~ +1 --FI eq ~.,, ± O's ± cq 1 18.± H ~ -H ±IA 2 Table 2 Seed germinatin data fr the riginal experiments. TT= tetrazlium test. r~.,,.~ tn H.,.,. Standard Standard i ~ ~.~ ~.- Days t Days t first cmplete ~~. Starting germ- germ- Taxn Lcatin date inatin inatin x s.,.. Carpdetus serratus Maruia Springs, Buller II Jun ±.5 Cprsma lucida Ahuriri Summit, 19 Feb ±.5 -H-H,'.4 eq ',. e R I cq ~ O", ~ '~ ~ O ~, ~, ',, '~ OO '~ O '~ ", Prt Hills, western Banks Peninsula Pittsprum eugeniides Riccartn Bush, Christchurch 3 Oct ±1.3 Pittsprum eugeniides Riccartn Bush, Christchurch II Jul ±.8 Pittsprum tenuiflium Ahuriri Summit, 2 May ±.8 Prt Hills, western Banks Peninsula Plagianthus regius Crater Rim,Prt Hills, 19 Feb ± western Banks Peninsula Pseudpanax arbreus Crater Rim,Prt Hills, 2 Apr ± western Banks Peninsula.~ ~ ~ ~ ~.., --" ~ ~ ~.... 9,~ ~ ~ ;~ ;~.~ ~ ~ ~ ~ 9,.,,, ;~ ~ ~ Pseudpanax arbreus Ahuriri Summit, Prt Hills, 3 Oct ±.6 western Banks Peninsula Pseudpanax crassiflius Ahuriri Summit,Prt Hills, 5 Jul ± western Banks Peninsula w w

7 36 New Zealand Jurnal f Btany, 1996, Vl. 34 \ Table 3: Genninatin data fr supplementary experiments. n = number f seeds tested; *main flush perid; +see text fr age f fruit w O + O ~D,..~ n~ c~ E n~,..~,..~ ~D Treatments Standard Percentage genninatin success per treatment Cllectin date; Grid reference Days t Days t Taxn (NZMS 26); first genn- cmplete Lcatin Altitude (m) Starting date inatin genninatin Standard Dark In-fruit Sil c/1 2.~ ~ c~~. ~ O ~D! ~'~ ~.~- GO,..~ Carpdetus serratus 1 Mar Mar I ~ i/h Taramakau Bridge, J32/6242 *Sep-Oct n = 25 n = 25 n = 5 Pq Kumara, Westland 4 n = 5 Cprsma lucida 6 Feb 1994 II Feb Staffrd cemetery, J32/53436 I n = 5 n = 5 near Hkitika, Westland 65 Pittsprum eugeniides 23 Dec Dec Riccartn Bush, M n = 25 Christchurch 9.5 Pittsprum eugeniides 25 Jul Jul Pq Sugarlaf Reserve, M36/ *Sep 1995 *Sep 1995 n = 25 n = 25 H I/h Prt Hills, 32 n = 5 n = 5 western Banks Peninsula O O O P',I O~ ~-~- ;~,-~ ~,-~ ~ -~- ~ r ~ O~-~-,-~ ~ ~. ~ ~ O~-~- ~ -~- ~ I/h ~,D ~!"~ tn 'h 'h I ~ t~ ~ P'-- I ~ r t'n '-~ r Pq pq ~1 + + Pittsprum tenuiflium 15 Nv I Dec Z Peel Frest, K n = 5 ::E Suth Canterbury 29 N Pittsprum tenuiflium 2 Apr Apr p Ahuriri Summit, M *Jul-Aug *Aug-Sep p; ::s Prt Hills, ~ r ~ O~,'-~ ~ O~ "-~ lib :~1 ~ _.~i "~ ~~ ~ ~ ~~: ~ ~. ~ ~:~ ~ "-- ~~ ~ --~ ~.~_. '- western Banks Peninsula n = 5 n = 5 ::: Plagianthus regius 23 Dec Dec a Riccartn Bush, M35! *Aug-Sep *Aug-Sep e:. Christchurch C\ /...l " , n = 5 n = 5 t... Plagianthus regius 2 Apr Apr p ::s Ahuriri Summit, M *Aug 1995 *Aug-Sep '::. Prt Hills, 46 n = '. western Banks Peninsula n = 25 '. \ ~,g Pseudpanax crassiflius 18 Jul Jul < Ahuriri Summit, M *Aug-Sep *Aug-Sep!?- Prt Hills, w western Banks Peninsula n = 5 n = 25.j:>.

8 Burrws---Germinatin f seven wdy plant species 361 Fig. 2 Germinatin curves fr Cprsma lucida seeds. 25- Cprsm /ucid Prt Hills, Banks Peninsula 9 Treatments standard dark x xx in fruit A z~ & sil " 2- Q"D "- ~ 15- ~ c loc [ ~ [ I t l X I x, 2 2 3, 2' 3,b 2b 3,, 2 FEB MAY[ JUN [ JUL [ AUG [ SEPT 199 treatment, the first seeds t germinate did s mre than three mnths after the experiment began (Fig. 2). The main germinatin flush fr standard and dark treatments was in June and July and final success (95%) the same fr bth. Seeds cllected in February 1994 germinated ver the winter, with 1% success in the standard and 94% in the dark treatment (Table 3). In the riginal experiment (Fig. 2), the sil treatment seeds were slwer t germinate than thse f the standard treatment and fewer germinated. Nne f the in-fruit treatment seeds germinated. Plagianthus Plagianthus fruit may persist n the parent tree, in sheltered places, frm December t April r May and smetimes thrugh the winter. Seeds were cllected in February and the first f these germinated in the standard treatment nearly tw mnths after the experiment began (Fig. 3). N germinatin ccurred frm early mid May t early July, but there was a flush in mid July. The last few seeds germinated spradically frm then until mid August. In this test, n Plagianthus dark treatment seeds germinated. In tw supplementary tests (Table 3), sets f dark treatment seeds cllected in December 1994 and April 1995 each germinated in late winter-early spring 1995, with 6% and 88% success, respectively. Seeds frm these cllectins, in the standard treatment, als underwent a flush f germinatin in late winter-early spring; a few seeds germinated earlier, in autumn and winter. In the riginal experiment, the sil and in-fruit treatment seeds f Plagianthus germinated mre slwly than in standard cnditins, with markedly lwer final success (Fig. 3). Pseudpanax arbreus Individual Pseudpanax arbreus plants flwer at varius times frm mid winter t well int the summer and different individuals in a ppulatin are bearing fruit ver a lng perid frm autumn thrugh t the fllwing spring. In 199, P. arbreus seeds were cllected in autumn. The first standard treatment seeds germinated in June, sme six weeks after the start f the experiment (Fig. 4). All seeds had germinated by the beginning f August. The dark and sil treatment seeds behaved similarly t ne anther, with lwer final success than the standard. N in-fruit treatment seeds germinated. In a secnd set fp. arbreus seeds cllected in spring, the standard treatment seeds began t germinate within 52 days (abut a week lnger than the first set); all seeds germinated ver a shrt perid (Fig. 4). Pittsprum tenuiflium Open capsules cntaining abundant seeds are maintained n Pittsprum tenuiflium plants until the seeds are remved by birds, usually by mid winter. Smetimes seeds persist in capsules until the fllwing spring r summer, 12 mnths r mre after flwering. In 1989 in the standard treatment, P. tenuiflium seeds cllected in autumn tk abut 12 weeks t cmmence germinatin (Fig. 5). During the pre-germinatin perid the mucilage-surrunded seeds were cvered by clnies f fungi and bacteria which appeared t be using the mucilage as a nutritive substrate. Germinatin ccurred at a steady rate and the last seeds t d s germinated by early Octber. The relatively lw germinatin success resulted frm lss f sme seeds which apparently were killed by fungi. Bth the dark and sil treatment seeds behaved very similarly t thse in the standard treatment. The seeds kept in-fruit (wet, with capsule valves) all failed t germinate.

9 362 New Zealand Jurnal f Btany, 1996, Vl ~ Plagianthus regius Prt Hills, Banks Peninsula Fig. 3 Germinatin curves fr Plagianthus regius seeds. Symbls as in Fig. 2. ~15- ~.. 2- ~lo- =g :~ 5-9 ~, ~ ~ A x a,./.,,, T~,, ' I I 21 I 2 I 2 3' l 2 s J 2 s I s FEB APR I MAY I JUL I AUG 199 In a later test frm an April 1995 cllectin f P. tenuiflium, in the standard treatment, the first seeds t germinate did s within 1 weeks, the last seeds germinated in August (Table', 3). Dark treatment seeds in this experiment behaved similarly t thse in the standard treatment, thugh the germinatin rate was slwer. Seeds cllected in Nvember 1994 were placed in standard cnditins in early December Only ne seed (2%) germinated, 77 days after the beginning f the experiment (Table 3). Carpdetus The fruit n individual Carpdetus trees are maintained green fr abut a year and ripen at varius times frm autumn t spring. Carpdetus standard treatment seeds began t germinate in August, ver tw mnths after the experiment started (Fig. 6). Althugh the germinatin patterns fr dark and sil treatments were similar t that in the standard, the percentage success was much lwer. N seeds germinated in the in-fruit treatment. In a subsequent standard treatment trial with Calpdetus seeds cllected in autumn (March 1994), sme germinated within a mnth, there was a halt in germinatin thrugh the cldest part f the winter, a flush in September-Octber, and cmpletin f germinatin in Nvember ('Fable 3). The pattern is very similar t that fr Plagianthus in the main tests as utlined abve. Pseudpanax crassiflius Pseudpanax crassoc'lius fruit ripen thrugh the winter and persist frm May t August. The P. crass!{lius standard treatment seeds all germinated in August, starting five weeks after the experiment was initiated (Fig. 7). Sil treatment seeds were slwer t germinate and with lwer percentage success. The dark treatment fr this species was accidentally expsed t light, s n results frm the main series are available. Hwever, in tests with seeds cllected in July 1995 (Table 3), 88% f the standard treatment seeds germinated in late winterearly spring f the same year, while 72% f the dark treatment seeds did s ver the same perid. Only 2% f the in-fruit treatment seeds in the riginal experiment germinated. Pittsprum eugeniides Pittsprum eugeniides green fruit (already abut six mnths ld) begin t ripen in summer but seeds may remain n the trees in dry fruit fr a further 6 mnths r mre befre being remved r shed. Pittsprum eugeniides seeds behaved differently in the standard treatment, accrding t the time f cllectin (Fig. 8). Amng seeds frm ripe fruit cllected in Octber 1989, sme germinated nearly tw mnths after the experiment started. The rate levelled ff in summer 1989/9 and there was n germinatin frm early January t mid May 199. The remaining seeds germinated in the winter f 199. A secnd set f seeds frm the same lcality, cllected in early July 199 and placed in standard cnditins, all germinated in August 199. N results are available fr the main series dark treatment seeds fr P. eugeniides as they were accidentally expsed t light during the curse f the experiment. Hwever, seeds cllected in July 1995 germinated in September f the same year in bth standard and dark cnditins, with 8% and 9% success, respectively (Table 3). The sil treatment fr P. eugeniides was als accidentally lst thrugh flding when a water pipe cnnectin brke. Germinatin success n sil fr seeds cllected in July 1995 was 65%. Seeds in the riginal in-fruit

10 Burrws---Germinatin f seven wdy plant species 363 P$udpnax rbreus Prt Hills, Banks Peninsula Pseudpanax arbrus Prt Hills, Banks Peninsula "1 2- ~* E IO-,-g IE z~ _~_ e x x x_ 31 ~ ~) ' '3'O' 13'I ' IO 2 3 I 2 I 2 I 2 I 2 i 3 APR I JUN I JUL I AUG I SEPT 1989 A ~n "~ 2] Fig. 4 Germinatin curves fr Pseudpanax arbreus seeds. Symbls as in Fig. 2. treatment (kept mist, tgether with the capsule 25- valves) failed t germinate, but in a set f seeds in this treatment cllected in July 1995, 2% germi- It} ~ 2-1:} nated (Table 3). In standard treatment cnditins, the,, final germinatin percentage fr seeds frm the ~ ~ /93 flwering, cllected in December 1994, was 8 t.- [= J- 9 12% (Table 3). c~ 5- ~ c- I "t 9! 1 I '1 I I 2 s i 2 s l OCT Nv l DEC I JAN Pittsprum tnuiflium Prt Hills, Banks Peninsula 9 9 t OZ~ DISCUSSION The results are cnsidered here (Tables 2, 3, Fig. 2-8) within the cnceptual framewrk utlined by Burrws (1994a, b), in which delayed germinatin f seeds, and resultant spread f germinatin thrugh time, is attributed t ne r mre f fur main causes. They are: physical cnstraint, impsed by thick, water-impervius (and gas- and light-impervius) seed cats; envirnmental cnstraint, due t unsuitable external cnditins in which the seeds find themselves; immaturity f embrys; true drmancy, impsed by relatively cmplex bichemical means, which may include the presence f inhibitry cmpunds in the seed cntents, testa, r investing materials (cf. Bewley & Black 1982; Mayer & Pljakff-Mayber 1989). Fr three species (Pseudpanax arbreus, Pittsprum eugeniides, and Carpdetus), each with presence f ripe fruit spread ver lng perids, there are intraspecific differences in germinatin respnse amng individuals in a ppulatin f adults accrding t the time when the seeds were cllected. Such differences may be related t crrespnding envirnmental differences experienced by each chrt f seeds, prir t the tests. 9 ;~/~_r_c~_r_.x ', --, ~x---r--x--r I 2 s I 2 3 I 2 s i MAY JUL I AUG I SEPT I OCT 1989 Fig. 5 Genninatin curves fr Pittsprum tenuiflium seeds. Symbls as in Fig. 2. Causes f bth interspecific and intraspecific variability f germinatin patterns will invlve cmplex interactins between the inherent physilgy f the seeds (partly affected by differential maternal influences n individuals amng chrts f seeds, cf. Gutterman (1992)) and the variable external envirnment, especially temperature and pssibly daylength. The causes f initial germinatin delay fr seeds in temperature, light, and misture cnditins suitable fr germinatin, are addressed first. In all f the seeds tested (including Plagianthus and Pseudpanax crassiflius, fr which at least sme seeds germinated when surrunded by pericarp), presence f the pericarp tissue inhibited germinatin. This phenmenn is widely knwn nw in New Zealand species (cf. Bannister & Jamesn 1994; Burrws 1994a, 1994b, 1994c, 1995a, 1995b, 1995c). Bannister & Jamesn (1994) fund that less

11 364 New Zealand Jurnal f Btany, 1996, Vl Carpdetus serratu$ Mruia Springs, Buller (/) Fig. 6 Germinatin curves fr Carpdetus serratus seeds. Symbls as in Fig. 2. ~ 15 '*- 9 OEc I c~ IDA Zh 9 5,,/~_, 9 ~ x, z 2' ' ' ' 3' ; ' ' ' ' JUN AUG I SEPT I OCT I NOV 199 i 2 I 3, I 2 I 2 3 s 2 3 than 1% f Pseudpanax crassiflius but abut 2% f P. arbreus seeds germinated when surrunded by the fleshy per9 tissue. In the present experiments, germinatin values fr these species infruit were 2% and zer, respectively. The differences in these tw sets f results may be attributable t real differences amng the seed prvenances used, r t differing cnditins under which the experiments were carried ut. These 'were nt specified in the Bannister & Jamesn (1994) accunt, but presumably were similar t thse emplyed by Mre et al. (1994) (seeds maintained in petri dishes n filter paper ver cttn wl, thrughly wet, 16 hur phtperid, 21 ~ In ther experiments (C. J. Burrws unpubl, data) it was fund that, if seeds f certain species (e.g., Cprsma rbusta, Griselinia littral9 Carpdetus serratus) were kept in the in-fi-uit treatment during the perid in 'which all standard treatment seeds germinated, there was n germinatin. Hwever, a few in-fruit seeds germinated after a further perid f tw mnths r mre. The in]hibitry effect f the per9 tissue, thus, was partly dissipated with time. Burrws (1993b) recrded vivipary in Cprsma rbusta and Ripgnum scandens seeds cllected late in the fruiting seasn. The mst likely cause f blckage f germinatin in the in-fruit treatments is the ccurrence f chemical inhibitrs in the fleshy fruit tissues r in the mucilage and capsule walls f Pittsprum spp. (cf. Burrws 1995c). Similar findings assciated with chemical inhibitrs in the fruit wall have been dcumented fr Eremphila in Australia (Richmnd & Ghisalberti 1994). It is f sme interest that the leachate frm capsule valves f dry-fruited Pittsprum eugeniides and P. tenu!flium, kept in a wet preparatin adjacent t the seeds, als inhibited their geixninatin. In a biassay experiment using lettuce seeds t test 25- " 2- e- g~gg ~ 5- - Ps e udpanax crassif lius Prt Hills, Banks Peninsula Lx 9 T.~,/~,X,-,,, 2 3' i,; 3',b 2' 3' JUL AUG I SEPT I OCT 199 Fig. 7 Germinatin curves fr Pseudpanax crass#hi9 seeds. Symbls as in Fig. 2. the effects f the capsule valve leachate frm P. tenuiflium, it was fund that nly 5% f the seeds had germinated after fur days and n rt hairs were present n the seedlings. In cntrast, 92% f seeds in the cntrl germinated within tw days and all had very lng rt hairs (C. J. Burrws unpubl, data). Tests f the mucilage which surrunds Pittsprum seeds are needed t ascertain whether it has inhibitry effects n seed germinatin. G. C. Platt (pers. cmm.) reprts that the germinatin f seeds f Pittsprum spp. is imprved by remval f the mucilage with detergent. Natural remval f this mucilage, as well as the inhibitry fleshy per9 frm ther seeds, is nnnally by passage thrugh birds (cf. Burrws 1994c). In the case f Plagianthus, r seeds f the ther species which fall directly t the grund still enclsed in fruit, remval f the per9 is by decay. This may be slw, thus prlnging the perid befre germinatin can start. In the present experiments, fungi and bacteria were respnsible fr remval f the mucilage frm the X x

12 Burrws---Germinatin f seven wdy plant species ~ c ~ ElO C i,. =g Pittsprum eugeniides Riccartn Bush, Christchurch Pittsprum eugeniides Riccartn Bush, Christchurch ~ ~E,- ~ 5- i e 3 I 2' 3 I z 3 i e 3 i OCT Nv l DEC IJAN MAY I JUN I JUL Fig. 8 Germinatin curves fr Pittsprum eugeniides seeds. Symbls as in Fig ~ l i l I i i 3O I 2 3 I 2 JUL I AUG 199 Pittsprum seeds. Sme seeds appeared t succumb t the micr-rganisms. Once the pericarp inhibitin effects are remved, delay f seed germinatin is cntrlled in ther ways. One f these is the inability t imbibe water. Nne f the seeds studied here appear t have cats which are quite impervius t water because they swell nticeably when wet. Hwever, water and gas entry t Plagianthus seeds may be slwed smewhat bth by the presence f the investing pericarp tissue and the hard seed cat. Tw ther pssible causes f germinatin delay are immature embrys, r inhibitrs in seed cats r embrys which blck the bichemical pathways fr germinatin (i.e., true drmancy, cf. Burrws 1994a, 1994b). Bth inhibitrs and immature embrys may ccur in the same seed. The nly infrmatin indicating that embry immaturity culd be invlved is the case f the tw Pittsprum species. The embrys in newly mature seeds are very small. It is difficult t find them when slicing the seeds t carry ut tretrazlium tests. By the time the seeds were abut t germinate, the embrys were at least an rder f magnitude larger. This alne culd be the main cause f the delay betbre these species began t germinate. True drmancy is a likely cause f germinatin delay in the ther species. One f the cmmnest ways in which seed drmancy f wild temperateclimate species can be vercme is by subjecting them t chilling treatment t simulate the winter cld perid which is needed befre germinatin ccurs (Mayer & Pljakff-Mayber 1989). Hwever, there are nly slight indicatins frm the present experiments that chilling is needed t encurage mst f the species being tested t germinate. Mst seeds f a winter cllectin f Carpdetus and spring cllectins f Pittsprum eugeniides and Pseudpanax arbreus germinated in warm seasns. In supplementary experiments fr Pittsprum eugeniides, P. tenuiflium, Plagianthus, and Pseudpanax crassiflius, standard treatment seeds underwent flushes f germinatin in late winter-early spring as temperatures were rising (Table 3). Mst seeds f Cprsma, Pittsprum tenuiflium, Pseudpanax crassiflius, a winter cllectin f Pittsprum eugeniides, and an autumn cllectin f Pseudpanax arbreus seeds germinated in winter. These winter-germinating seeds, therefre, are nt inhibited by winter cnditins. Hwever, lw temperature effects befre the seeds were remved frm the trees might have induced drmancy in seeds f sme f the same species which germinated in spring r summer (see abve). Mre et al. (1994) fund that imbibed seeds f P. eugeniides and P. tenuiflium shwed almst n germinatin and a marked lss f viability when kept mist, in the light, at 21 ~ fr three t fur mnths. Hwever, seeds frm the same sets, after chilling at 4~ fr eight weeks, germinated with 93% and 2% success, respectively, when kept at 21~ After 12 weeks at 4~ 5% fp. tenuiflium and 1% f P. eugeniides seeds germinated in the refrigeratr. These results are nt quite in accrd with cnclusins frm the present experiments that chilling is nt necessarily required t break drmancy in these seeds. The glasshuse minimum temperatures in 1989 and 199, when the experiments were carried ut, were clse t 3~ s natural chilling culd have affected the results. Cntrlled temperature experiments in the 1-2~ range are needed t clarify uncertain pints.

13 366 New Zealand Jurnal f Btany, 1996, Vl. 34 Burrws (1994a) has shwn that seeds f many lwland wdy plants d nt have any particular requirement fr lw temperature treatment befre they will germinate. Germinatin in seasns when the misture supply is reliable seems t have been an evlutinary imperative affecting them. Seeds f sme New Zealand wdy species have a mre clear-cut respnse t artificial chilling (e.g., Hheria glabrata, Haase (1987); Discaria tumatu, Kegh & Bannister (1992)). These are species f mainly inland lcatins which experience mderately lw t severe winter temperatures. In the present experiments, results which may indicate that there is a degree f verwinter drmancy vercme by an episde f chilling are thse fr Plagianthus and an autumn cllectin f Carpdetus. In these tw cases, abut half f the seeds germinated in autumn, nne (,r very few) in early winter, and the last seeds germinated in late winter (when lw temperatures were actually mre severe than earlier in the winter) Amng the seed sets f 9 winter-germinating species, the germinatin rate is ften slw and this is prbably attributable t the slwing effects f lw temperatures n physilgical prcesses (i.e., t envirmnental cnstraint, cf. Burrws 1994a, 1994b). It is pssible, als, that different seed prvenances fr the plant species culd respnd differently t the experimental cnditins. If bichemical blcking, interacting with requirements fr lw temperature treatment, is invlved with delayed germinatin in species such as Carpdetus, Pittsprum eugeniides, r Plagianthus the present results shw that it is manifested in cmplex ways. Further detailed experimentatin is needed t islate the causal factrs. The verall effect f the delays in germinatin (and the differing degrees f expressin f the delays in particular chrts f seeds) is that germinatin f seeds f all the species studied can be well spread ut in time. This applie,; least t sets f seeds f Pseudpanax crassiflius and a winter cllectin f Pittsprum eugeniides, which each cmpleted germinatin f all seeds in the sets within tw weeks. The ptential variatin in germinatin times revealed by the experiments is als likely t be expressed in natural situatins. As illustrated by the experimental results abve, in nature there wuld be a cnsiderable amunt f flexibility f seed germinatin in respnse t the climatic effects experienced thrugh the seasns. It seems likely that n lng-term sil seed banks culd ccur fr tlhe investigated species, except Plagianthus. Hwever, experiments n germinatin f buried seeds are needed t w,~rify this assumptin. All f the species can behave as clnisers int shrub cmmunities, bracken, r even in pen, grassy r stny sites. All species als establish in at least mderately shaded sites under frest canpies. The seed germinatin prperties f these species, revealed in the experiments described here, are in fair agreement with what we knw f their regeneratin eclgy. Further experimentatin n seedlings and saplings is needed t prvide an integrated picture f the relatinships between germinatin and establishment and the relative differences frm species t species. ACKNOWLEDGMENTS Financial assistance fr the wrk described here was btained frm the University f Canterbury Research Cmmittee and the Department f Plant and Micrbial Sciences, University f Canterbury. The paper was prepared with the help f funds frm the Ltteries Grants Bard. I am grateful t David Cnder fr help in maintaining the experiments, t Lee Lenard fr drawing diagrams, t Nancy Gh fr typing the script, and t Guy Richmnd and an unidentified referee fr cmments which helped t imprve the text. REFERENCES Allan, H. H. 1961: Flra f New Zealand. Vl. I. Wellingtn, Gvernment Printer. Bannister, P.; Bridgman, J. 1991: Respnses f three species f Pseudpanax t lw temperature stratificatin, remval f fruit flesh and applicatin f gibberellic acid. New Zealand jurnal f btany 29: Bannister, P.; Jamesn, P. E. 1994: Germinatin physilgy f seeds frm New Zealand native plants. In: Clbear, P.; Crnfrd, C. A.; Pllck, K. M. ed. Seed develpment and germinatin. Agrnmy Sciety f New Zealand special publicatin N. 9. Pp Bewley, J. D.; Black, M. 1982: Seeds; physilgy f develpment and germinatin. New Yrk, Plenum Press. Burrws, C. J. 1993a: Germinatin requirements f the seeds f native trees, shrubs and vines. Canterbury Btanical Sciety jurnal 27: Burrws, C. J. 1993b: Vivipary and effects f maternal tissues n germinatin in sme New Zealand seeds. Canterbury Btanical Sciety jurnal 27: Burrws, C. J. 1994a. The seeds always knw best. New Zealand jurnal f btany 32:

14 Burrws----Germinatin f seven wdy plant species 367 Burrws, C. J. 1994b: Germinatin experiments with seeds frm the native New Zealand wdy plant flra. In: Clbear, P.; Crnfrd, C. A.; Pllck, K. M. ed. Seed develpment and germinatin. Agrnmy Sciety f New Zealand special publicatin N. 9. Pp Burrws, C. J. 1994c: Fruit, seeds, birds and the frests f Banks Peninsula. New Zealand natural sciences 21: Burrws, C. J. 1995a: Germinatin behaviur f the seeds f the New Zealand species Fuchsia excrticata, Griselinia littralis, Macrpiper excelsum, and Melicytus ramiflrus. New Zealand jurnal f btany 33: Burrws, C. J. 1995b: Germinatin behaviur f the seeds f the New Zealand species Aristtelia serrata, Cprsma rbusta, Crdyline australis, Myrtus bcrdata, and Schefflera digitata. New Zealand jurnal f btany 33: Burrws, C. J. 1995c: Germinatin behaviur f the seeds f six New Zealand wdy plant species. New Zealand jurnal f btany 33: Cnnr, H. E.; Edgar, E. 1987: Name changes in the indigenus New Zealand flra, and Nmina Nva IV, New Zealand jurnal f btany 25: Gutterman, Y. 1992: Maternal effects n seeds during develpment. In: Fenner, M. ed. Seeds: the eclgy f regeneratin f plant cmmunities. Wallingfrd Cmmnwealth Agricultural Bureaux Internatinal. Pp Haase, P. 1987: Eclgical studies n Hheria glabrata (Malvaceae) at Arthur's Pass, Suth Island, New Zealand. New Zealand jurnal f btany 25: Hrrell, B. A.; Jamesn, P. E.; Bannister P Prpagatin and regulatin f phase change in sme heterblastic species. Cmbined prceedings f the Internatinal Plant Prpagatrs'Sciety 25: Kegh, J. A.; Bannister, P. 1992: A methd fr inducing rapid germinatin in seed f Discaria tmatu. New Zealand jurnal f btany 3: Mayer, A. M.; Pljakff-Mayber, A. 1989: The germinatin f seeds. 4th ed. Oxfrd, Pergamn. Mre, S.; Bannister, P.; Jamesn, P. E. 1994: The effects f lw temperatures n seed germinatin f sme New Zealand species f Pittsprum. New Zealand jurnal f btany 32: Richmnd, G. S.; Ghisalberti, E. L. 1994: Seed drmancy and germinatin mechanisms in Eremphila (Mypraceae). Australian jurnal Of btany 42: