Flower quality and fruit size in kiwifruit (Actinidia deliciosa)

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1 New Zealand Journal of Crop and Horticultural Science ISSN: (Print) (Online) Journal homepage: Flower quality and fruit size in kiwifruit (Actinidia deliciosa) H. G. Mcpherson, A. C. Richardson, W. P. Snelgar, K. J. Patterson & M. B. Currie To cite this article: H. G. Mcpherson, A. C. Richardson, W. P. Snelgar, K. J. Patterson & M. B. Currie (2001) Flower quality and fruit size in kiwifruit (Actinidia deliciosa), New Zealand Journal of Crop and Horticultural Science, 29:2, , DOI: / To link to this article: Published online: 22 Mar Submit your article to this journal Article views: 634 View related articles Citing articles: 9 View citing articles Full Terms & Conditions of access and use can be found at

2 New Zealand Journal of Crop and Horticultural Science, 2001, Vol. 29: /01/ $7.00 The Royal Society of New Zealand Flower quality and fruit size in kiwifruit (Actinidia deliciosa) H. G. MCPHERSON The Horticulture and Food Research Institute of New Zealand Ltd Mt Albert Research Centre Private Bag Auckland, New Zealand A. C. RICHARDSON The Horticulture and Food Research Institute of New Zealand Ltd Kerikeri Research Centre P. O. Box 23 Kerikeri, New Zealand W. P. SNELGAR K.J. PATTERSON M. B. CURRIE The Horticulture and Food Research Institute of New Zealand Ltd Mt Albert Research Centre Private Bag Auckland, New Zealand Abstract Kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R, Ferguson 'Hayward') vines were grown at five sites that represented the climatic range of the major kiwifruit growing regions of New Zealand. Hydrogen cyanamide was applied to half the vines at three of the sites. Measurements of flower quality over two seasons were used to determine if this was linked to fruit weight at harvest. There was a progressive increase in ovary fresh weight and ovary dry weight from warmer to cooler sites. Hydrogen cyanamide increased ovary fresh weight by between 6 and 20% and fruit weight by up to 11% Corresponding author. H00010 Received 13 April 2000; accepted 30 March 2001 at the two warmest sites. Variation in ovary fresh weight and dry weight accounted for some of the variation in fruit weight 170 days from flowering in the first season, but over both seasons, by itself, had no predictive value. The highest correlation between fruit weight and flower quality across both seasons was with the ratio of pedicel length to seed number (r 2 = 0.56). The relatively consistent relationships that have previously been found between crop load and average fruit weight and between flower quality and fruit weight at harvest did not apply over different seasons and regions. Keywords Actinidia deliciosa; kiwifruit; flower quality; fruit size; fruit growth; hydrogen cyanamide INTRODUCTION Season-to-season variation in the fruit size of kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson 'Hayward') poses difficulties in management of vines and distribution and marketing of the fruit. Changes in the relationship between mean fruit size and crop load from year to year, provides an indication of the magnitude of seasonal variation. Cooper & Marshall (1990) reported a 20 g range in mean fruit weight over 3 years for vines with a similar crop load and management, whereas Snelgar et al. (1986) found a 17 g difference over two seasons and Van Oostrom (1985) found a 10 g difference. A significant amount of seasonal variation in kiwifruit size at harvest is established early in the fruit growth period. Hall et al. (1996) found that c. 75% of the variation in mean fruit volume and 80% of the standard deviation at harvest were already determined by 50 days after flowering. This is about the time that the second, slower phase of fruit growth starts and is only one third of the way through the fruit growth period. Fruit size is determined by cell number and cell size, so factors which influence it are likely to be active during periods of substantial cell division and

3 94 New Zealand Journal of Crop and Horticultural Science, 2001, Vol. 29 expansion before and after anthesis. Unlike most deciduous fruit crops where flower bud differentiation occurs in the season before their emergence, in kiwifruit it occurs only c. 3 weeks before budbreak (Linsley-Noakes & Allan 1987; Snowball & Walton 1992) which is typically 7-12 weeks before anthesis in New Zealand (McPherson et al. 1992). Therefore flower quality is likely to be influenced during the weeks before anthesis. Almost one third of the number of cells present in mature kiwifruit are present at flowering (Hopping 1976) and the majority of cell division has been completed 50 days from flowering (Hopping 1976; Woolley et al. 1992; Currie 1997). The size and quality of kiwifruit flowers has been shown to be important in determining final fruit size. Several authors have found that early flowers had larger ovaries with more locules and ovules than late flowers on the same vine and they produced larger fruit (Lai et al. 1990; Lawes et al. 1990; Cruz- Castillo et al. 1991). Comparisons between early and late flowers may be a result of competition for resources within the vine and positional effects (Smith et al. 1994). It has not been established whether these relationships between flower and fruit size apply between regions and seasons. Processes that occur during the 7-week period of rapid fruit growth immediately after anthesis may also affect fruit size at harvest. The effectiveness of pollination is important. Currie (1997) found that poorly pollinated kiwifruit had fewer cells and a lower fruit growth rate. Individual fruit weights are highly correlated with seed number and increases in fruit weight of between 3.6 and 5.6 g/100 seeds have been found (Hopping 1990; Snelgar et al. 1991; Snelgar & Martin 1997). Vascular development of the pedicel or fruit may also influence fruit growth. Fruit size was found to be highly correlated (r ) with the diameter of fruit pedicels (Lai et al. 1990) however because the pedicel measurements were made at harvest it was not clear when their influence may have been important. In satsuma mandarins, Marsh et al. (1999) found that 9 weeks after anthesis, the cross-sectional area of vascular bundles was highly correlated (r 2 = 0.98) with fruit volume at harvest. It is not clear whether this is due to assimilate transport limitations or merely an effect of sink strength. A further consideration in assessing the impact of flower quality on fruit growth is the widespread commercial use of hydrogen cyanamide. Hydrogen cyanamide is applied before budbreak to promote flower production by reducing abortion of basal flower buds (Walton & Fowke 1993). Increases in fruit size have also been reported. Henzell et al. (1992) found that in the Bay of Plenty, New Zealand, the mean weight of fruit increased by from 1 to 15% over five seasons when hydrogen cyanamide was used despite a 20% increase in average crop load. Costa et al. (1997) found that, in southern Italy, hydrogen cyanamide increased average fruit size and the percentage of marketable fruits, increasing the yield of marketable fruit by between 8 and 515% over four seasons. As the fruit size at harvest has been largely determined by 50 days from flowering (Hall et al. 1996), it must be an expression of differences that exist earlier than that, possibly by the time of fruit set. The objective of this study is to explore variability in flower quality between seasons and regions, and seek relationships with fruit size at harvest. This may provide a basis for understanding the causes of the variation in fruit size at harvest, and to develop predictive tools. Clearly, when withinseason forecasts are required, the earlier in the season the predictions can be made, the better. MATERIALS AND METHODS Kiwifruit vines (A. deliciosa 'Hayward') were grown on three HortResearch Research Orchards (Kerikeri 35 10'S, 'E; Te Puke 37 50'S, 'E; andriwaka 41 07'S, 'E). Two commercial orchards near the Te Puke Research Orchard were also used, one was 120 m higher than the research orchard ("TP Hi", 37 53'S, 'E); and the other 90 m lower ("TP Lo", 37 49'S, 'E). Measurements were made over two seasons 1996/ 97 and 1997/98. All vines were more than 10 years old, trained on T-bar trellises and managed using standard commercial practices (Sale 1983). Pollination was by bees, combined with supplementary pollination using the PollenAid system. At the research orchard sites, five blocks of vines were selected, each with two pairs of vines. Hydrogen cyanamide was applied randomly to one of each pair used at a rate of 3.12 kg active ingredient per 100 litres, between 34 and 65 days before natural budbreak. In the commercial orchards, 10 vines in a single row were used with no application of hydrogen cyanamide. Two typical fruiting canes were chosen on each vine (one cane per side). At the mid-point of flowering, two fruiting laterals positioned at the midpoint along each fruiting cane, were chosen and

4 McPherson et al. Flower quality and fruit size 95 tagged. On each shoot, two terminal flowers that were at anthesis and at nodes other than the proximal three were tagged close to 50% flowering. One flower from each pair was chosen at random, and harvested for destructive flower quality assessments. The remaining flower of each pair was left on the vine and used for fruit growth measurements throughout the season. Flowers sampled for quality measurements were immediately placed in "ziptopped" plastic bags, transported to the laboratory in cooled polystyrene containers and analysed within 24 h of harvest. In the laboratory, pedicel and ovary dimensions were measured with electronic callipers (Bower Instruments, Bradford, United Kingdom). The callipers were modified to prevent compression of flower tissues by reducing the spring tension between the measuring arms and adding large flat plates to the calliper jaws. Ovaries were removed from flowers by trimming off the stylar whorls, stamens, and sepals at the junction with the ovary. Measurements were made of ovary maximum diameter, minimum diameter, and fresh weight. Ovary dry weight was measured after drying in a fan oven at 65 C to constant weight. Carpel number was assessed for each flower by counting the number of styles and assuming a 1:1 style:carpel ratio (McNeilage 1988). Measurements were also made of pedicel length, maximum diameter, and minimum diameter (measured mid-way along the pedicel). Fruit growth measurements were made on the remaining fruit of each pair (n = 40 for each treatment at each site). Fruit length, maximum diameter, and minimum diameter were measured non-destructively with hand-held electronic callipers (Mitutoyo Instruments, Kawasaki, Japan) at weekly intervals from 2 to 9 weeks after flowering and then at 2-weekly intervals thereafter. Fruit fresh weight was estimated from the relationship: FW = LxD m^_ xd^ where: FW = fruit fresh weight (g); L = length of fruit (mm); D max = maximum diameter of the fruit at the equator of the fruit (mm); and D min = minimum diameter of the fruit at the equator of the fruit (mm) (Snelgar et al. 1992). At harvest, all the monitored fruit were picked and weighed. In addition, all the remaining fruit on the experimental vines were picked and graded to determine fruit number, mean fruit weight, and crop load (number of fruit/m 2 of canopy area). Seed numbers were estimated by first extracting the seeds from each fruit using a pectolytic enzyme (Rohapect VR-C enzyme, Carter Associates, Auckland, New Zealand) at c. 5 g/litre with a fungicide (Captan, 1 g/litre) added to inhibit fungal growth. Once separated by sieving and drying at 60 C, the seeds from each fruit were weighed and a sample of 50 seeds counted and weighed. The total number of seeds was then estimated by multiplying the average seed weight from the sample by total seed weight. Fruit size at harvest was estimated for 170 days from flowering because, by this stage, fruit growth had stopped or nearly stopped (below 0.3 g/day). The estimate was made using linear interpolation between the two fortnightly measurements that were closest to 170 days from flowering and which fell either side of it. On three sets of data measurements did not quite extend to 170 days, so it was necessary to extrapolate by 2-6 days. Data analysis was based on treatment means for each site (i.e., mean of four fruit from each of 10 vines). It should be noted that the sampling system used in this experiment provided a focus on modal units in order to reduce variability. This was done as follows. Vines were chosen near the centre of blocks to avoid the effects of shading. Typical fruiting canes were selected and from them, fruiting laterals positioned near the mid-point of the canes were chosen. Only terminal flowers from lateral node positions 4 and higher were used for analysis. Results for fruit weights are of individual tagged fruit, not the average fruit weight of all fruit on the vine (except for calculation of crop load, that was based on whole vine harvests). The results should be interpreted in this light. If the design had aimed to randomly sample from each block, a much wider range of flower and fruit attributes would have resulted. RESULTS AND DISCUSSION Crop load In this experiment the site mean crop load for each treatment varied between 23 and 53 fruit/m 2 and it seemed appropriate to consider normalising our fruit weight data to a common crop load. The relationship between fruit weight and crop load shows that with the same vines and treatment, substantial increases in crop load can occur with either no change in fruit weight, a decrease in mean fruit weight, or even an

5 - \ ' ' ' ' - -,.. \ \ '. ' " " :, _ 96 New Zealand Journal of Crop and Horticultural Science, 2001, Vol. 29 : 3> 1) 5 c CO <D Control Hydrogen cyanamide T2 i K 1 \ T2m \ L2 /... \ R2tt Vi / 1,.L1'» i - >»K2 am H i» - Fig. 1 Effect of crop load on fruit weight at: Kerikeri (K); Te Puke (T); Riwaka (R); Te Puke Hi (H); and Te Puke Lo (L) in 1996/97 (1) and 1997/98 (2), with and without application of hydrogen cyanamide. 80- i i Crop load (fruit/m) increase in mean fruit weight between seasons (Fig. 1). These results suggest that, in making comparisons across seasons and regions, crop load does not have a sufficiently consistent impact on fruit size to warrant normalising fruit weight to a common crop load. This is consistent with the finding of Cooper et al. (1988) and Cooper & Marshall (1990) that the relationship between crop load and fruit size varies from year to year and possibly with other variables such as site and plant density. The data of Richardson & McAneney (1990) showed a 0.6 g decrease in fruit weight for each fruit/m 2 increase in crop load over the range of crop loads found in this experiment. However there was considerable variability in their data, which had been measured in different seasons at different sites. Non-destructive estimates of ovary weight Some linear dimensions of ovaries, that can be measured non-destructively, were correlated with ovary fresh weight and dry weight. This could prove useful where non-destructive, in situ estimates of ovary fresh and dry weight are required. Ovary maximum and minimum diameters were a useful predictor of ovary fresh weights (FW) across all sites: ovary FW (mg) = ovary max. diam. (mm), r 2 = 0.90 ovary FW (mg) = ovary min. diam. (mm), r 2 = 0.75 This opens the possibility of studying relationships on an individual fruit basis, rather than on a population basis. For ovary dry weight, the predictive value of ovary maximum and minimum diameters was substantially lower (r 2 = 0.62 and r 2 = 0.60, respectively). Pedicel maximum diameter was also correlated with ovary fresh weight and dry weight (DW): ovary FW (mg) = pedicel max. diam. (mm), r 2 =0.58 ovary DW (mg) = pedicel max. diam. (mm), r 2 = 0.69 Regional and seasonal variation Fruit weights were lower in 1996/97 (99 g) than in 1997/98 (111 g) when averaged across all sites (P < 0.05). The range in the first year (31 g) was much greater than in the second (18 g). Fruit weight variability was dominated by relatively low fruit weights in the first season at the three sites in the Te Puke region (Fig. 2A). The differences between years were much smaller at the most northern and southern sites (Kerikeri and Riwaka). We have no explanation for the lower fruit weights in that one region, in one year. Ovary fresh weight increased progressively from warmer to cooler sites in the absence of hydrogen cyanamide (Fig. 2B). Ovary dry weights also increased from the warmer to the cooler sites (Fig. 2C). This may result from the longer period taken from budbreak to flowering at the cooler sites (McPherson et al. 1992). It is interesting to note that the fresh weight and dry weight of dormant buds at Riwaka is actually lower than at the warmer sites (McPherson et al. 1997). The differences in ovary

6 McPherson et al. Flower quality and fruit size 97 Fig. 2 Several fruit and flower variables at Kerikeri, Te Puke Hi (TP Hi), Te Puke Research Orchard (TR), Te Puke Lo (TP Lo), and Riwaka for: 1996/97 (Y1), and 1997/98 (Y2) with and without application of hydrogen cyanatnide. A, fruit weight; B, ovary fresh weight; C, ovary dry weight; D, pedicel length; and E, seed number/fruit. Asterisks denote a significant difference between the control and hydrogen cyanamide treatment (P< 0.05). _ CD r 110 en 100 I 90- LL e r Q ra O E CD 0_ (0 O c I * * * *. * 1 * * t Control Hydrogen cyanamide.m "* * \.. v * * * * t * / / / ' Ji? / D E Y1 Y2 Y1 Y2 Y1 Y2 Y1 Y2 Y1 Y2 * * Kerikeri TP Hi TR TP Lo Riwaka fresh weight and dry weight between years varied from site to site. There were no noticeable trends in pedicel length between sites and seasons, however pedicels where shortest in the control vines at the warmest site, Kerikeri (Fig. 2D). The number of seeds in each fruit was 13% higher (P < 0.05) in the second year of the experiment than the first (Fig. 2E) but there was no trend from site to site. In the present experiment, ovary fresh weight varied from 0.3 to 0.4% of fruit fresh weight 170 days from anthesis, which is similar to the results of Gould et al. (1992). In the first year ovary fresh weight averaged 0.38% of final fruit weight and in the second year, which had larger fruit on average, it was only 0.33%. This implies that factors other than flower size have a major impact on final fruit size.

7 98 New Zealand Journal of Crop and Horticultural Science, 2001, Vol. 29 S ' " i i 1996/ / Fig. 3 Fruit weight as a function of the ratio of pedicel length to seed number/fruit. 90H 80-? = 56% Fruit weight = pedicel length/seed number 70 -> 1 1 i Pedicel length/seed number (mm/fruit) Hydrogen cyanamide Applications of hydrogen cyanamide to vines were associated with significant increases in fruit weight at Kerikeri in 1997/98 (11% increase) and 9% increases in fruit weight on vines at Te Puke in both seasons (Fig. 2A). Greater fruit size was associated with increases in ovary fresh and dry weight, pedicel length and seed number, although differences were not always significant (Fig. 2B,C,D,E). An analysis of the growth of fruit at the Kerikeri site in 1997/98 showed that effects of hydrogen cyanamide could be seen throughout fruit growth (Patterson et al. 1999). A 6% decrease in the size of fruit on hydrogen cyanamide treated vines at Riwaka, possibly because of late application of chemical, was associated with smaller ovaries in flowers and a significantly shorter pedicel. It seems likely that hydrogen cyanamide effects on fruit size reported in this and previous studies (Henzell et al. 1992; Costa et al. 1997) are the result of flower size, although differences in flowers, for example at the Kerikeri site in 1996/97, were not always translated into fruit size. Effects of flower quality on fruit weight In 1996/97 the flower attribute most closely correlated with fruit size was pedicel length at anthesis. Short pedicels were correlated with large fruit size: fruit weight (g) = pedicel length (mm), r 2 = 0.62 When ovary dry weight was introduced as a second variable, 89% of the variation in final fruit weight was accounted for: fruit weight (g) = ovary DW (mg) pedicel length (mm) Other regressions involving pedicel minimum and maximum diameter, various combinations of maximum and minimum diameter, seed number and ovary fresh weight, in combinations of two variables, gave correlations of between 0.71 and Carpel number varied from 36.4 to 43.1 per fruit but showed no useful correlation with fruit weight. The high correlations established between flower quality and fruit weight 170 days from flowering in 1996/97 suggested that flowers could provide a valuable early indicator of fruit size at harvest. However, in the following season (1997/98) flower quality had limited predictive value. The highest correlation found between fruit weight and flower quality across both seasons was with the ratio of pedicel length to seed number (r 2 = 0.56, Fig. 3). Pedicel length was negatively correlated with fruit weight and seed number was positively correlated with fruit weight. By including ovary fresh weight

8 McPherson et al. Flower quality and fruit size 99 as an additional variable, a higher proportion of the variance was accounted for: fruit weight (g) = ovary FW pedicel length (mm)/seed number, r 2 = 0.67 Patrick (1988) suggested that the supply of assimilate to meristematic sinks will be primarily affected by the source-path system and that for expansion of storage sinks, sink processes are likely to dominate in regulation of partitioning. Both source-path and sink strength limitations could regulate kiwifruit growth during the period of up to 50 days from anthesis. The negative correlation between pedicel length and fruit weight in the present experiment is consistent with the concept of a sink-path limitation that resistance to assimilate flow is proportional to the length. However, the difference in pedicel length may simply be a consequence of the sink strength. A similar correlation was found between the cross-sectional area of dorsal vascular bundles 9 weeks after anthesis and final fruit volume in satsuma mandarins (Marsh et al. 1999). Such affects on assimilate transport may be hormonally regulated (Patrick 1987). Burge et al. (1990) have shown that application of GA 3 to kiwifruit canes after budbreak increased pedicel length whereas PP333 decreased it, with a corresponding decrease or increase in fruit weight. The positive correlation between seed number and fruit weight in the present experiment is consistent with significant regulation by sink strength. Currie (1997) found some evidence that poorly pollinated kiwifruit had fewer cells and a lower fruit growth rate throughout development, including the period up to 42 days from full bloom. It is therefore possible that seeds act to regulate post-anthesis cell division that sets the potential fruit weight by 50 days after full bloom. Previous studies (Lai et al. 1990; Lawes et al. 1990; Cruz-Castillo et al. 1991) have found a correlation between the weight and dimensions of the ovary and the size of the fruit. However their comparisons were made between early and late flowers on the same vines, where resource limitation and positional effects may predominate. Variation in ovary fresh weight and dry weight accounted for some of the variation in final fruit weight in the first season of this study, however, there was a low correlation over both years. These comparisons were made between five sites, two seasons, and with hydrogen cyanamide applied to one set of vines. Sampling was also restricted to flowers opening near peak flowering to eliminate time of flowering effects. The low importance of ovary weight (i.e., "starting capital" for fruit growth) across seasons and regions, implies that the differences in fruit size at Day 50 that are found to be highly correlated with fruit size at harvest (Hall et al. 1996) are the result of something that happens either: (1) after flowering and during the first 50 days of fruit growth; or (2) before flowering but is not expressed during the first 50 days of fruit growth; or (3) before flowering and is expressed before flowering but was not detected by our measurements. CONCLUSIONS We had anticipated that crop load, hydrogen cyanamide applications, and differences in flower quality would explain a large proportion of the variation in the size of kiwifruit at harvest. However this was not the case. The number of fruit carried by vines did not have a consistent effect on final fruit size, although a consistent relationship is needed as the basis for thinning techniques. Application of hydrogen cyanamide to vines did influence fruit size, both positively and negatively, and this appears to be because of the size of flowers. As most of the variation in fruit size has been determined by 50 days from mid-bloom (Hall et al. 1996), factors that influence cell division and expansion before this time predominantly, influence final fruit size. In this study, development of the pedicel (assimilate transport) and seed number (sink strength) appear to be key determinants of growth, whereas ovary size is of lesser importance. Although flower attributes were correlated with final fruit size in some cases, the relationship was not robust enough to be used predictively. Clearly, either the experimental approach taken did not sufficiently explore the relationship between flower quality and fruit size or there are other factors, which have a significant impact on fruit development up to 50 days after anthesis and hence final fruit size. ACKNOWLEDGMENTS We thank the following staff who maintained vines and collected data: Robyn McQueen and Ted Dawson, Kerikeri; Wendy Scott, Philip Martin, and Joanne Craig, Te Puke; Heather Adams, John Campbell, Joanne Stokes, and Greg Lupton, Riwaka. Thanks also to Helen Paul for

9 100 New Zealand Journal of Crop and Horticultural Science, 2001, Vol. 29 collating and checking data. We thank Grahame Hopcraft, Kiwifruit Investments and Ken Arnold, Beresford Farms for the use of their orchards. This work was funded by the New Zealand Foundation for Research, Science and Technology, Contract No. CO6622. REFERENCES Burge, G. K.; Spence, C. B.; Broadbent, N. D. 1990: Effects of gibberellic acid and paclobutrazol on fruit size, shape, locule number and pedicel length of kiwifruit. Scientia Horticulturae 42: Cooper, K.; Marshall, R. 1990: Improving fruit size through crop-loading and canopy management. New Zealand Kiwifniit Special Publication No. 3: Cooper, K. M.; Marshall, R.; Atkins, T. A. 1988: Controlling fruit size for profit. New Zealand Kiwifruit Special Publication No. 2: 7-8. Costa, G.; Vizzotto, G.; Lain, O. 1997: Fruiting performance of kiwifruit cv. Hayward affected by use of cyanamide. Acta Horticulturae 444: Cruz-Castillo, J. G.; Lawes, G. S.; Woolley, D. J. 1991: The influence of the time of anthesis, seed factors, and the application of a growth regulator 50: mixture on the growth of kiwifruit.actahorticulturae Marsh, K. B.; Richardson, A. C.; MacRae, E. 297: A. 1999: Currie, M. B. 1997: Source-sink relations in kiwifruit: carbohydrate and hormone effects on fruit growth at the cell, organ and whole plant level. Unpublished PhD thesis, Massey University, Palmerston North, New Zealand. Gould, K. S.; Watson, M.; Patterson, K. J.; Barker, K. A. 1992: Fruit cell type juice or flavour. New Zealand Kiwifruit Special Publication No. 4: Hall, A. J.; McPherson, H. G.; Crawford, R. A.; Seager, N. C. 1996: Using early-season measurements to estimate fruit size at harvest in kiwifruit (Actinidia deliciosa). New Zealand Journal of Crop and Horticultural Science 24: Henzell, R. F.; Briscoe, M. R.; Gravett, I. 1992: Improving kiwifruit vine productivity with plant growth regulators. Acta Horticulturae 297: Hopping, M. E. 1976: Structure and development of fruit and seeds in Chinese gooseberry (Actinidia chinensis Planch.). New Zealand Journal of Botany 14: Hopping, M. E. 1990: Floral biology, pollination and fruit set. In: Warrington I. J.; Weston. G. C. ed. Kiwifruit science and management. Auckland, Ray Richards. Pp Lai, R.; Woolley, D. J.; Lawes, G. S. 1990: The effect of inter-fruit competition, type of fruiting lateral and time of anthesis on fruit growth of kiwifruit. Journal of Horticultural Science 65: Lawes, G. S.; Woolley, D. J.; Lai, R. 1990: Seeds and other factors affecting fruit size in kiwifruit.ac Linsley-Nokes, G. C.; Allan, P. 1987: Effects of winter temperatures on flower development in two clones of kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson). Scientia Horticulturae 33: McNeilage, M.A.I 988: Cytogenetics, dioecism and quantitative variation in Actinidia. Unpublished PhD thesis, University of Auckland, Auckland, New Zealand. McPherson, H. G.; Hall, A. J.; Stanley, C. J. 1992: The influence of current temperature on the time from bud break to flowering in kiwifruit (Actinidia deliciosa). Journal of Horticultural Science 67: McPherson, H. G.; Snelgar, W. P.; Manson, P. J.; Snowball, A. M. 1997: Bud respiration and dormancy of kiwifruit (Actinidia deliciosa). Annals of Botany Early- and mid-season temperature effects on the growth and composition of satsuma mandarins. Journal of Horticultural Science and Biotechnology, 74: Patrick, J. W. 1987: Are hormones involved in assimilate transport? In: Hoad G. V.; Jackson, M. B.; Lenton, J. R. ed. Hormone action in plant development: a critical appraisal. London, Butterworths. Pp Patrick, J. W. 1988: Assimilate partitioning in relation to crop productivity. Hortscience 23: Patterson, K. J.; Snelgar, W. P.; Richardson, A. C; McPherson, H. G. 1999: Flower quality and fruit size of Hayward kiwifruit. Acta Horticulturae 498: Richardson, A. C.; McAneney, K. J. 1990: Influence of fruit number on fruit weight and yield of kiwifruit. Scientia Horticulturae 42: Sale, P. 1983: Kiwifruit culture. Wellington, P.D. Hassleberg, Government Printer. Smith, G. S.; Gravett, I. M.; Edwards, C. M.; Curtis, J. P.; Buwalda, J. G. 1994: Spatial analysis of the canopy of kiwifruit vines as it related to the physical, chemical and postharvest attributes of the fruit. Annals of Botany 73:

10 McPherson et al. Flower quality and fruit size 101 Snelgar, W. P.; Manson, P. J.; Martin, P. J. 1992: Influence of time of shading on flowering and yield of kiwifruit vines. Journal of Horticultural Science Van Oostrom, A. J. 1985: Kiwifruit (Actinidia chinensis Planch.) water use characteristics, and physiological responses to the presence and absence or irrigation 67: in an Ohinepanea Loamy Sand. Snelgar, W. P; Martin, P. J. 1997: Relationship between Unpublished MSc thesis, University of Waikato, leaf area index and fruit size in kiwifruit.actahorticulturae Hamilton, New Zealand. 444: Snelgar, W. P.; Martin, P. J.; Manson, P. J. 1991: Influence of shelterbelts on pollination of kiwifruit. Acta Horticulturae 297: Snelgar, W. P.; Thorpe, T. G.; Patterson, K. J. 1986: Optimal leaf:fruit ratios for fruit growth in kiwifruit. Acta Horticulturae 175: Snowball, A. M.; Walton, E. F. 1992: Flowering in kiwifruit. New Zealand Kiwifruit Special Publication No. 4: Walton, E. F.; Fowke, P. J. 1993: Effect of hydrogen cyanamide on kiwifruit shoot flower number and position. Journal of Horticultural Science 68: Woolley, D. J.; Lawes, G. S.; Cruz-Castillo, J. G. 1992: The growth and competitive ability of Actinidia deliciosa "Hayward' fruit: carbohydrate availability and response to the cytokinin-active compound CPPU. Acta Horticulturae 297: