Fruit set Hormones Mineral Nutrition HOS 6546 Spring 2012
Julian C. Crane HortScience, Vol. 4(2): 108-111. 1969 California Objective: Determine the relationship of seeds in fruit and the correlation between the seeds and the activity of endogenous growth hormones.
Crane proposed that the developing seeds with their high levels of hormones act as mobilization centers of nutrients required for their growth and surrounding fruit tissues High concentrations of these substances in seeds attracts metabolites to the fruit and enable it to compete with other growing organs of the plant
INDUCTION OF PARTHENOCARPY AND INCREASED FRUIT SET In attempt to increase fruit set in conditions unfavorable for pollination Crane, 1965, using 4-amino-3,5,6-trichloropicolinic acid (strong auxin) demonstrated indirectly that each of the 3 types of endogenous growth promoting hormones can be supplied by plant parts other than the seeds. Clore, 1965, grapes dipped at pre-bloom and post bloom (GA3) produced from 88-96% seedless berries, matured 28 or greater days earlier with lower sugar/acid ratios than controls. Dennis & Egerton, 1966, GA3 reduced fruit set and inhibited flower bud formulation in open pollinated apples. Sparks, 1967, delayed maturity and increased total weight of pecans using Potassium Gibberellate.
Lewis, et al., 1965, fruit set in parthenocarpic navel orange was correlated with a high level of citrus auxin. The period of maximum fruit drop coincided with a change in accumulation pattern of CA and the initial detection of an inhibitor. No citrus auxin, just normal auxin Experiments have shown that exogenous ABA: Promotes abscission of young fruits Causes cessation of extension growth and onset of bud dormancy Promotes parthenocarpy Accelerates senescence Inhibits or promotes flower induction in different species Inhibits auxin-mediated Avena coleoptile growth Inhibits gibberellin controlled responses Interacts with cytokinins
Ethylene concentrations are present in various fruits throughout their development, stimulated by climatic conditions When cytokinins, gibb, auxins decline to low levels in fruit (figs), ethylene mobilizes the continued flow of nutrients to fruit in maturing stages Auxins stimulate ethylene production by roots, stems, leaves and fruits In natural parthenocarpy, the development of specialized structures in the ovaries has been correlated with high auxin levels Following leaf or fruit removal reproductive organs dominate in assimilate distribution vs. vegetative organs
Reproductive organs divert the flow of nutrients from vegetative organs greatly in some situations Mobilization of metabolites and other materials into developing fruits is mediated by their hormonal-directed transport from other organs Developing seeds contain large quantities of hormones and are the richest source of these materials. Enables dominance over vegetative structures Abscission, senescence and polar transport have been related to the mobilization of plant constituents
Eliezer E. Goldschmidt. HortScience, Vol. 11(2)95-98, April, 1976 Israel Objective: Present data on the quantitative estimation of growth substances from citrus organs, review the hormonal balance of citrus tissues in relation to processes of growth and development.
Auxins IAA Gibberellins Cytokinins Abscisic Acid ABA Other growth inhibitors
Auxins Auxins = Indole compounds (generally accepted) Indolylacetic Acid (IAA) Some questions as to the difference of IAA and Citrus Auxin Testing found large amounts of auxin in flower organs, particularly in flower petals High auxin activity in ovaries and fruitlets during anthesis and fruit set Ovaries of seedless cultivars more auxin than seeded Auxins also play a role in the more advanced stages of fruit growth and maturation
Sharp peak in auxin activity at 10 days after bloom. Rapid decrease approaching zero levels after full bloom IAA and Indoleacetamide could not be found 2 months after full bloom
Gibberellins First identified in 1959 in tissue of higher plant Young lemon and orange fruits found to contain at least 3 Gibb like substances - 1965 2 identified as GA1 and GA9 At least 3 Gibb like substances have been described in the flavedo of maturing orange fruits - 1974 Flower parts (petals & stamens) shown to contain at least 3 biologically active Rf zones GA1 & GA3 have been found during the initial stages of fruit development - 1969 Rate of fruit growth proved to be correlated with the concentration of Gibb during the cell division period Total Gibberellins per fruit increased during the cell enlargement stage, slightly preceding the increase in fruit weight and volume
Cytokinins First identified in 1966 in Lemon seed extract Found in all flower organs but particularly higher in petals Similar to Gibberellins in that smooth fruit generally contains less than rough skin fruit, also flavedo more than albedo Assumed that Cytokinins play an important role in rootcanopy relationships, affecting senescence processes
ABA / Growth Inhibitors Large amount are present in citrus Could possibly mask the presence of growth promoters or possibly interfere with their quantitative estimation if not recognized Abscisic acid (ABA) detected in lemon juice in 1967 ABA detected in orange flavedo 1973 Other nuetral (non-polar) growth inhibitors, rather than ABA, found in shoots, developing fruit and leaves An upsurge of ABA occurs in drought-stressed leaves, neutral growth inhibitors remain level Young fruitlets show a peak concentration of ABA during the first few days after anthesis 1975 Generally fruits maintain a stable, low level of ABA until a gradual rise occurs approaching maturation A decrease in ABA-like growth inhibitors has been found in regreening Valencias 1973
Krezdorn, A.H. and H.D. Brown. 1970. Increasing yields of the Minneola, Robinson and Osceola varieties with gibberellic acid and girdling. Proc. Fla. State Hort. Soc. 83:29-34 GA increased set and fruit size in grapes Tested on Orlando tangelo Girdling also worked well on both crops Purpose: To expand tests
Materials and Methods Test concentration, time of application and trees age for GA response, as indicated in tables Evaluate girdling also, as single knife cut
Counting area to evaluate flowers and subsequent set
No statistics
Full bloom was best timing
2, 4-D did not increase set over GA alone
All concentrations equal effect
Girdling and GA equal effect Neither treatment did well in some old, low vigor trees
Summary Girdling and GA both worked well to enhance set Full bloom best timing, but GA concentrations from 10 to 25 ppm equal effect Did not test girdling plus GA on same trees, nor times of girdling
Takahashi, N., I. Yamaguchi, T. Kono, M. Igoshi, K. Hirose and K. Suzuki. 1975. Characterization of plant growth substance in Citrus unshiu and their change in fruit development. Plant and Cell Physiol. 16:1101-1111 Drop waves after bloom noted and varied in 2 years Assume hormonal control Some previous work, but felt re-evaluation justified, particularly integrating measurement of 2 major plant hormones, ABA and auxin
Material& Methods Fruits collected on dry ice, held at -20 C and extracted within 2 weeks for hormones ABA, and auxins analyzed
General fruit size data of samples, not very important
Peaks at 5 and 35 days AFB, not drop data and no ABA in this graph
Peaks at 7-10 and 35 days AFB for auxins and ABA
Method detects IAA, relationship to data not very clear from figure
Same pattern in 1973, higher early peak
Fruit abscission stronger in 30-35 day peak than in 10 day AFB peak.
Summary ABA and IAA changed coincided with abscission waves This is not cause and effect data. Why would auxin increase cause drop? Auxins NAA increases drop at beginning of May-June drop (10 weeks AFB in Florida) No separation of abscising fruitlets from retained
M. Talon and E.J. Primo-Millo,. 1984. Endogenous gibberellins as related to fruit set in citrus varieties of the navel group.. Proc. International Citrus Congress 1984;200-201 All plant growth regulators have been implicated in fruit set and development GA applied effects fruit set, but natural levels in relationship to set not well studied Purpose: to monitor hormonal GA through set period
Materials & Methods Used Washington N and Navelate, a low set strain of navel Samples solvent extracted, tested for total GA, chromatographed and assayed by barley endosperm test
GA activity in different flower or ovary tissue Navalate usually higher in GAs in flower buds and immature ovaries.
Navelate had higher GA in flower buds and immature ovaries
Summary GA higher in FB and immature ovaries of Navalate, which sets poorly Conclude GA may not be most important, but GA lower in mature ovary, after flowering. This is time that Krezdorn got positive response. Points out need to measure all hormones in tissue.
Talon, Zacarias and Primo-Millo. 1990. Hormonal changes associated with fruit set and development in mandarins differing in their parthenocarpic ability. Physiologia Plantarum (ft) 79:400-406 Background: Several authors have suggested that the control of fruit development in seedless and seeded varieties is carried out through the hormonal balance between ABA and auxin-like substances and ABA and GAlike substances, respectively (Garcia-Papi, 1984). Seedless Clementine mandarins are self-incompatible and without cross-pollination show a very low ability to set fruits. On the other hand, exogenous applications of GA in these varieties, increase fruit set. Another study; a treatment of GA3 in pistils in citrus flowers resulted in a stronger mobilization of metabolites of young ovaries, which appears essential for fruit set and development (Powell and Krezdorn, 1977) Varieties with a high male sterility and naturally parthenocarpic, such as Satsuma, have a high fruiting ratio. In these cases, GA applications have not been efficacious in increasing fruit set (Coggins and Hield, 1968)
Purpose & Materials and Methods Purpose: Determine differences in hormonal content of Satsuma and Clementines mandarins in reproductive organs. Study of the relationship of hormonal content and the parthenocarpic ability in each variety. Estimation of GAs, IAA and ABA levels during the early phases of fruit growth. M&M Clementine and Satsuma (seedless cultivars) Fruitlets were collected at different stages: A; bud containing pollen mother cells before the prophase of the first meiotic division (-21 DAA); C: ovary at stage of young pollen (-12 DAA); E: ovary at pollination (0 DAA); F ovary at petal fall (6 DAA) and H & I: developing fruits. 200 fruits were taken at each point for growth.
Hormonal changes associated with fruit set and development in mandarins differing in their parthenocarpic ability Talon, Zacarias and Primo-Millo. 1990. M&M: (cont) To determine ovaries and fruit drop, they took 10 populations of 250 tagged fruits on 10 different trees. Growth and abscission parameters were studied over two consecutive seasons. Hormonal identification and determination are very well described, including all the steps of the extraction and purification. They used appropriate and modern equipment. Hormone estimations were determined twice in fruits from 2 consecutive seasons. (ft) satsuma Results and discussion: Fig 1 show the increase in fruit weight. It is possible to divide it into three stages according to Bain (1958). In both cultivars the period of cell division and slow growth lasted about 1 month including flowering. The following 5 months are rapid growth until the beginning of maturation. There were two waves of drop (Fig 2) in both cultivars; first one at anthesis and petal-fall stages and included the drop of flowers and developing ovaries. Second, developing fruits about 1 month later. Clementine, self-incompatible mandarin had a higher % of fruit drop, setting only 3% of the initial fruits in comparison with 23% in Satsuma.
Hormonal changes associated with fruit set and development in mandarins differing in their parthenocarpic ability Talon, Zacarias and Primo-Millo. 1990. Results and discussion: Table 1 shows the identification of all the GAs found in this study. This was determined by comparison with reference spectra (Takahashi et al, 1986) and from their relative retention times (ft) on capillary GC. All of them are 13-hydroxylated GAs. Meaning it is the major GA biosynthetic pathway in both vegetative and reproductive tissue. The presence of these GAs in Satsuma ovaries suggests that this GA biosynthetic pathway operates in the reproductive tissue of this variety.
Hormonal changes associated with fruit set and development in mandarins differing in their parthenocarpic ability Talon, Zacarias and Primo-Millo. 1990. Results and Discussion: Results by bioassay suggest Clementines have low amounts of GA3 in comparison with Satsuma (fig 3 A&B) The physiologically-active Gas, in the early stage, are probably involved in cell expansion in the fruit (as previous studies showed in peas and tomatoes). These results also suggest that seedless fruit of Clementine do not reach GA threshold levels required during anthesis for adequate fruit set and development. On the other hand, application of GAs are more effective between anthesis and 2 weeks later. Seedless varieties have lower levels of GAs (ft) GA3 in Clementines vs Satsumas Fig 4 show the levels of IAA free and bound. Both trends are similar in free IAA (A) so it seems unlikely that IAA content was a limiting factor in controlling fruit set. The decline of free IAA coincided with the increase of conjugate (B), suggesting a precursor-product relationship between these two substances.
Hormonal changes associated with fruit set and development in mandarins differing in their parthenocarpic ability Talon, Zacarias and Primo-Millo. 1990. Results and discussion: Cohen and Bandurski, suggest that in these tissues conjugates of IAA could act as a temporary storage form, controlling the concentration of free IAA. In this study the correlation does not appear in Satsuma (fig 4 B) Previous reports said that the levels of bound IAA appear to be constant independently of the levels of free IAA; this is a contradiction with the results found here. (ft) Free ABA in both cultivars reached higher levels at the petal fall stage. Developing fruitlets of Clementine contained more free ABA than Satsuma (Fig 5 A). In contrast, Satsuma had a large amount of bound ABA The physiological role of conjugate ABA is not clear. It is assumed to be an inactive storage form by which free ABA may be sequestered (Milborrow, 1983) Total ABA in these two cultivars was similar. satsuma satsuma
Hormonal changes associated with fruit set and development in mandarins differing in their parthenocarpic ability Talon, Zacarias and Primo-Millo. 1990. Overview: Hormonal status of developing fruits of both cultivars studied differed mainly during the stage of cell (ft) division and early stages of cell enlargement. During this period the low ability to set parthenocarpic fruits appears to be related to lower levels of GAs, a low capability to conjugate ABA and a higher ability to conjugate IAA. M & M well explained. Good statistical analysis of all the data
Sagee, O and Erner, Y. 1991. Citrus fruit set: carbohydrate, hormone, and leaf mineral relationships. IN Manipulation of fruiting. Wright, C.J. (ED).233-242 General background: In Citrus almost 95% of reproductive organs abscise within two months after anthesis. There are some cultivars that require pollination and seed development for fruit set while others set seedless fruit. It appears that in seedless cultivars a pollen stimulus is sufficient to set fruit. Monselise (1972) and Krezdorn (1981) hypothesized that in these cultivars, fruit tissue (other than seeds) provide stimuli that establish a high metabolic gradient and divert the flow of nutrients from vegetative to fruitlet. It is proven that leafy inflorescences have a higher fruitset, while abortion is nearly complete on leafless inflorescences (Erner and Bravdo 1983) except in grapefruit and lemon. Lenz, 1966; Moss, Steer and Kriedemann 1972; Sanz et al, 1987 propose that the young leaves supply photosynthates to the developing fruits in amount sufficient to mitigate the effect of competition from other metabolic sinks; while fruitlet borne on leafless inflorescenses have to mobilize their assimilates from one-year-old leaves.
How growth regulators appear in this picture? It is thought that hormones attract assimilates and minerals. GA increased fruit set and yield dramatically when pollination was limiting (Clementine and Orlando); however, neither GA or NAA is capable of increasing fruit set when fruitlets are in leafy inflorescences.
Gibberellins and abs acid contents during flowering and fruit set of Shamouti orange.1991. Sagee, O. and Y. Erner. Background: At this time, the idea was common that fruitlets borne in leafy inflorescences had a better supply of photoassimilates than fruitlets borne in leafless ones. On the other hand, Erner and Bravdo 1983 had suggested that the contribution of inflorescence leaves was perhaps other than just a photosynthate supplier. There were several studies about GA and ABA, sometime showing contradictory results. Comprehensive data of the role of both hormones at the same time was lacking. That is why the purpose of this work was an attempt to examine GA and ABA in inflorescence organs simultaneously during fruit development. The relationship between them and the comparison between both kind of inflorescences was to be studied. M & M: Shamouti orange budded on Palestine sweet lime Samples were taken from both kind of inflorescenses LY (terminal flower with four young leaves) and LS (a single flower) HPLC and GC-EC were used, respectively, to separate and identify the plant hormones.
Gibberellins and abs acid contents during flowering and fruit set of Shamouti orange.1991. Sagee, O. and Y. Erner. Results and discussion: Within 2 months after FO, there weren t significant differences in fruitlet fresh weight between those borne on LY or LS. What about after this period? It is only different in number of fruitlets or those borne in LY are bigger? GA content: GA (ng/g fresh weight) increased during the first week after FO, and then decreased continuously during the following 7 weeks (Table 1). On a fresh weight basis, no significant differences were observed between LY and LS, indicating that changes in GA levels, per se, are probably not the causal factor in the preferential fruit set on LY. TOTAL GA, (ng per fruitlet) consistently increased with time (Table 2). As reported before, GAs have a role in controlling fruit development during the cell division period. decreased sharply without sign. differences between both LY and LS
Gibberellins and abs acid contents during flowering and fruit set of Shamouti orange.1991. Sagee, O. and Y. Erner. Results and discussion: ABA content: Table 1 and 2; both kind of inflorescences have the same tendency but LS had a higher concentration. ABA increased with growth and at 7 and 33 days after FO, it is possible to see significant differences between both LY and LS and GA content at 33 days. This higher ABA, might be connected to metabolic events leading to fruitlet drop (Takahashi, 1975); or may already be an integral part of an ongoing process of abscission in LS.. Table 3 presents the ratios of GA to ABA. In fruitlets borne on LY this ratio was higher than in those on LS. This higher ratios of growth promoter to growth inhibitor in LY during the first two months might be related to their superiority in fruit set.
Gibberellins and abs acid contents during flowering and fruit set of Shamouti orange.1991. Sagee, O. and Y. Erner. Overview: According with their results, fruitlets which survived during the first two months after FO, didn t have significant differences between LY and LS in fresh weight accumulation. This apparent inconsistency is because they didn t include fruitlets that abscise (smaller and most of them in LS). According to this study, during the first two months after FO, the ratio of GA to ABA is in favor of persistence of LY-borne fruitlets and the drop of LS-borne fruitlets. The picture arising is that probably cytokinins from the roots, auxins from shoots, water and nutrients, all together may be involved in controlling fruit set. No sequence of large and small fruitlets at mid abscission times as likely to set and likely to fall categories of each. Also, no data about when majority of fruitlets of leafy and leafless classes fell.
Barry, G.H. and J.P. Bower. 1997. Manipulation of fruit set and stylar-end fruit split in Nova mandarin hybrid. Scientia Hort. 70:243-250 Nova is self incompatible and too seedy if cross pollinated It also tends to split Purpose: GA and girdling trials were conducted to test if increased fruit set occurred and if peel splitting was reduced
Materials & Methods GA 10 or 15 ppm and girdling were applied at petal drop or fruitlet drop Other treatments, such as nutritional sprays were also tested.
Girdling was more effective than GA, which was better than other treatments. No girdling plus GA treatment
Similar results, but no increase from nutritionals added to girdling
Summary Girdling better than GA, but no girdling + GA treatment Are they additive or not? Some tendency for nutrient additions to increase girdling results, usually numerical increases only.
Sanz, A., C. Monerri, J. Gonzalez-Ferrer and J.L. Guardiola. 1987. Changes in carbohydrates and mineral elements in Citrus leaves during flowering and fruit set. Physiol. Plantarum 69:93-98. Under Mediterranean conditions fruit set and not flowering determine yields Many buds drop even before the flowers fully open Spring growth is a large sink for nutrients and carbohydrates Purpose: Assess carbohydrate and mineral changes at this early stage of fruit growth
Materials & Methods Samples collected from 9 orchards over time for analyses of: Nutrients in leaves Carbs Other tests to evaluate sink strengths
N P K N, P and K in young and old leaves during flowering and early fruit set. Old leaf values depressed. Young leaves start low and build up nutrients
Growth rate Dry weight
Old leaves and young leaves have high carbohydrate levels which then decline. Old leaves are high before flowering and decline during early bud development and bloom. Young leaves decline later, supplying to fruitlets? Note starch
Young leaves do not recover even if flowers removed.
Small changes but similar to vegetative, carbohydrates less than in vegetative flush leaves maybe due to smaller leaves, not sign.?
Done later, more like flowering inflorecsenses Clear effect of fruit removal on increased nutrient levels and decreased starch (sink loss reduced Pn)
Summary N and K declined in old leaves and then recovered during flowering Drop periods coincided with lowest old leaf nutrient and carbohydrate levels suggesting possible role in drop (competition). Authors state small leaf size of inflorescence leaves is not due to presence of flower(s) Probably did not compare early enough (pre-flowering sink)
Erner, Y. 1989. Citrus fruit set: Carbohydrate, hormone and leaf mineral relationships. In, Manipulation of fruiting. (Wright, CJ (Ed); pp233-242 Review of earlier work Details of studies on carbohydrates, hormones and nutrition
Hard to follow, how to separate leaf A vs B treatment?
Leafless fruit larger, more sugar and label activity??
Generally more set in leafy and if vegetative shoot nearby(?)
N levels jumping up and down with time; old leaves lower than young, fruitlet N not very different
Small difference in inflorescence type, but large fruit set difference
Higher GA
Higher ABA
Summary Leafy set more but had lower N, dilution? N improved set but not of any type GA higher 7 days in leafless fruitlets, but in leafy mature leaves and young leaves ABA higher in leafless fruitlets through 33 DAFO and their mature leaves 63 DAFO ABA closest relationship to abscission
Albrigo, L.G. 1997. Competition factors influencing fruit set of citrus. IN Citrus Flowering and Fruiting Short Course 73-74 Competition factors probably main reasons for fruit adjustments after pollination-fertilization issues are settled Carbohydrates, nutrients, hormonal levels as influence sink strength and essential requirements?? Water stress may be another important factor Spring foliar nutrients increased yields in flatwoods
Proc. Fla. State Hort. Soc. 120:64 66. 2007..Effect of Winter- and Springtime Applications of Foliar Urea, NPK, or K-phosphite Sprays on Productivity of Citrus in Central Florida L. GENE ALBRIGO Foliar nutrition in spring increased yields in flatwood groves Tested if these sprays would benefit higher producing groves They did not, therefore flatwood response may be due to poor root health and foliar application is a good substitute.
GENERAL OVERVIEW: Fruit set is a complex phenomenon under three levels of regulation Activator of genetic program in seedled fruits is an external stimuli: pollination after activation, carbohydrates, mineral elements and water play an important role in later fruit set
GENERAL OVERVIEW: Pollination-dependent SEEDED FRUIT Parthenocarpic or self-incompatible SEEDLESS FRUIT high content of GA in seeds In general applications do not increase fruit set Valencia, clementines and some mandarins GA applications increase fruit set and yields Grapefruit, Navels, some mandarins and other hybrids