Delayed Fruit Development Research Articles

Enhancing Uniform Sprouting, Yield, and Quality in Grapevines: The Impact of Hydrogen Cyanamide (50% S.L) Treatment

Grape (Vitis vinifera L.) is considered as one of the most important commercial fruit crops in temperate, tropical and subtropical regions of the world. In India grape cultivation in tropical and subtropical regions assumes great significance, but one of the biggest issues preventing grapes from being produced in warm climates has been the lack of or insufficient winter chilling. Under these circumstances, there is uneven bud bursting, flowering, and delayed fruit development. The most crucial component of grape development is, consistent bud breaking is required to increase grape quality and maturity. Many plant growth regulators are used to promote bud burst and increase the proportion of bud break. Several locations across the world utilize plant growth regulators to intentionally cause bud break. The application of Hydrogen Cyanamide (H2CN2) during pruning time of grapes, helps to enhance growth uniformity, encourage earlier and more even bud break, raises the proportion of fruit buds, berry set, number of clusters per vine, weight of clusters, and dimensions of clusters. It also gives positive response to various metabolic activities; maximize yield and Maturity, Fruit quality, as well as production efficiency. In grape orchards, it is commonly used to promote consistent and improved bud burst, shortened flowering period, and boost output.

Heat Stress Leads to Poor Fruiting Mainly Due to Inferior Pollen Viability and Reduces Shoot Photosystem II Efficiency in “Da Hong” Pitaya

High summer temperatures (day/night: 40 °C/30 °C) are known to cause poor fruiting, reduced fruit/seed weight, and delayed fruit development in the “Da Hong” red-fleshed pitaya (Hylocereus polyrhizus); however, the mechanisms of these effects are unknown. This study examined how high temperature (HT, 40 °C/30 °C) affects stamen and pistil fertility through pollination combinations and fruit set in “Da Hong” pitaya and evaluated photosystem II (PSII) efficiency in yellowed shoots (cladodes). The in-vitro pollen germination rate was significantly higher at optimal temperature (OT, 30 °C/20 °C) than at HT, which was also associated with a reduced flower length, poor fruit set, small fruit size, and low number of seeds after self-pollination. Meanwhile, fruit set and fruit development were remarkably improved by using the pollens taken from plants grown at OT and moderate temperature (MH, 35 °C/25 °C) after mutual cross pollination, indicating that the reduction in seed number caused by incomplete fertilization due to inferior pollen viability was the main cause of poor fruiting under HT rather than pistil or photoinhibition, although HT treatment was linked to reductions of PSII efficiency at both the adaxial and abaxial ends of shoots. The results suggested that pollen viability was most affected under HT stress; thus, yielding remarkably reduced fruiting.

Semi-Transparent Organic Photovoltaics Applied as Greenhouse Shade for Spring and Summer Tomato Production in Arid Climate

Recognizing the growing interest in the application of organic photovoltaics (OPVs) with greenhouse crop production systems, in this study we used flexible, roll-to-roll printed, semi-transparent OPV arrays as a roof shade for a greenhouse hydroponic tomato production system during a spring and summer production season in the arid southwestern U.S. The wavelength-selective OPV arrays were installed in a contiguous area on a section of the greenhouse roof, decreasing the transmittance of all solar radiation wavelengths and photosynthetically active radiation (PAR) wavelengths (400–700 nm) to the OPV-shaded area by approximately 40% and 37%, respectively. Microclimate conditions and tomato crop growth and yield parameters were measured in both the OPV-shaded (‘OPV’) and non-OPV-shaded (‘Control’) sections of the greenhouse. The OPV shade stabilized the canopy temperature during midday periods with the highest solar radiation intensities, performing the function of a conventional shading method. Although delayed fruit development and ripening in the OPV section resulted in lower total yields compared to the Control section (24.6 kg m−2 and 27.7 kg m−2, respectively), after the fourth (of 10 total) harvests, the average weekly yield, fruit number, and fruit mass were not significantly different between the treatment (OPV-shaded) and control group. Light use efficiency (LUE), defined as the ratio of total fruit yield to accumulated PAR received by the plant canopy, was nearly twice as high as the Control section, with 21.4 g of fruit per mole of PAR for plants in the OPV-covered section compared to 10.1 g in the Control section. Overall, this study demonstrated that the use of semi-transparent OPVs as a seasonal shade element for greenhouse production in a high-light region is feasible. However, a higher transmission of PAR and greater OPV device efficiency and durability could make OPV shades more economically viable, providing a desirable solution for co-located greenhouse crop production and renewable energy generation in hot and high-light intensity regions.

Overexpression of an EIN3-binding F-box protein2-like gene caused elongated fruit shape and delayed fruit development and ripening in tomato

Ethylene signaling converges on the ETHYLENE-INSENSITIVE3 (EIN3)/EIN3-like (EIL) transcription factors to regulate a wide range of developmental processes in plants. EBF1/2 (EIN3-binding F-box protein 1 and 2) negatively regulate the ethylene signaling pathway by mediating the degradation of EIN3/EIL proteins. We uncovered previously that SlEBF1 and SlEBF2 are involved in ethylene response, plant senescence, and fruit ripening in tomato. The present study reports on the identification of a novel tomato F-box gene, designated as SlEBF2-like due that its encoded protein is greater similarity to SlEBF2. The SlEBF2-like promoter region contains three ethylene-response elements (EREs). SlEBF2-like is upregulated by ethylene and downregulated by ethylene inhibitors in tomato seedlings. It is dynamically expressed in flowers during bud-to-anthesis and anthesis-to-post-anthesis transitions, and at the onset of fruit ripening, suggesting its role in these situations where ethylene is required for flower opening and fruit ripening. SlEBF2-like overexpression leaded to fruit elongation, caused ripening and color change to start from fruit bottom and expand gradually to the pedicel, and strongly delayed fruit development and ripening in tomato. Our study indicates that the novel EBF gene, SlEBF2-like, is involved in fruit development and ripening via regulating the ethylene response in tomato.

Cluster illumination differentially affects growth of fruits along their ontogeny in highbush blueberry ( Vaccinium corymbosum L.)

Abstract Shading highbush blueberry plants generally leads to a delayed fruit development. Experiments have been performed to study the effects of light on fruit growth independently from the rest of the canopy. Clusters were shaded during different fruit growth periods. The equatorial diameter of the fruits as a function of days after full bloom followed a double-sigmoidal growth pattern, being fitted using a Gompertz II nonlinear mixed model, and absolute growth rates were obtained from each fitted model. Both whole-cycle shaded and second-stage shaded fruits showed a delayed peak in absolute growth curves with respect to both first-stage shaded and whole-cycle unshaded controls. Our results suggest that deficiency of light during the last stage of highbush blueberry fruits may lead to a substantial delay (of about 10–16 days) in harvest as compared with well-illuminated fruits. In order to estimate the contribution of intrinsic fruit photosynthesis to its own growth at different stages, clusters were subjected to girdling on their peduncles at different times. Girdling just before the second-stage resulted in fruits gaining between 35 and 40% of dry weight in comparison with the controls. This suggests that fruit photosynthesis may play a relevant role in fruit growth during the second sigmoidal stage, which in turn may contribute to explain the delayed growth observed in shaded fruits.

Haloxylon ammodendron (Amaranthaceae) fruit development delay caused by post-flowering non-inductive photoperiod

Haloxylon ammodendron (C. A. Mey.) is one of the economically and ecologically important desert trees used for sand fixation. The ovary of H. ammodendron is found not to swell after flowering in spring until at the end of August or early September in western China. However, what happens for ovary at anatomic level in that period and which crucial ecological factor regulates the phenomenon of H. ammodendron have not been fully understood. To characterize the phenomenon and explore the crucial environmental regulating factors, we carried out the morphological and anatomic observations at the different development stages of the fruits and three single-factor experiments (low air temperature, sufficient soil moisture, and short day length). Our results showed that under the natural conditions, the ovary of H. ammodendron after flowering developed slowly and the morphological changes of fruits were not significant for the period from May to August and after late August or early September; and then the ovary developed rapidly and matured in October. Cell division in embryo was observed to start approximately 25 days after flowering (DAF) and just developed to globular embryo stage at mid-August. Photoperiod was identified as the pivotal environmental factor regulating the fruit development of H. ammodendron. Moreover, the threshold value of day length for the fruit development was 14.0 h. A long day (>14.0 h) treatment began from 5 DAF could delay fruit development of H. ammodendron while a short day (<14.0 h) treatment could accelerate it. Moreover, a further longer day treatment (>15.0 h) could also delay fruit development even when they had developed for a long time (110 DAF). The present study indicated that H. ammodendron adopted a reproductive strategy of delayed fruit development and this strategy helps it survive and obtain offspring in harsh desert habitats.

Partner choice through concealed floral sugar rewards evolved with the specialization of ant-plant mutualisms.

Obligate mutualisms require filtering mechanisms to prevent their exploitation by opportunists, but ecological contexts and traits facilitating the evolution of such mechanisms are largely unknown. We investigated the evolution of filtering mechanisms in an epiphytic ant-plant symbiotic system in Fiji involving Rubiaceae and dolichoderine ants, using field experiments, metabolomics, X-ray micro-computed tomography (micro-CT) scanning and phylogenetics. We discovered a novel plant reward consisting of sugary sap concealed in post-anthetic flowers only accessible to Philidris nagasau workers that bite through the thick epidermis. In five of the six species of Rubiaceae obligately inhabited by this ant, the nectar glands functioned for 10d after a flower's sexual function was over. Sugar metabolomics and field experiments showed that ant foraging tracks sucrose levels, which only drop at the onset of fruit development. Ontogenetic analyses of our focal species and their relatives revealed a 25-fold increase in nectary size and delayed fruit development in the ant-rewarding species, and Bayesian analyses of several traits showed the correlated evolution of sugar rewards and symbiosis specialization. Concealed floral nectar forestalls exploitation by opportunists (generalist ants) and stabilizes these obligate mutualisms. Our study pinpoints the importance of partner choice mechanisms in transitions from facultative to obligate mutualisms.

PHYSIOLOGICAL RESPONSE OF VACCINIUM CORYMBOSUM 'ELLIOTT' TO SHADING NETS IN MICHIGAN

Plants of the ‘Elliott’ highbush blueberry (16-year-old, planted at 3 x 1 m) were grown in a sandy loam soil under colored shade nets (white, red, black and no net) of different density (25, 50 and 75% of shading) in Gobles, Michigan, USA, during 2006-07. Treatments were assigned randomly with 3 reps, and established as a continuum of 4 rows with 6 plants in each row. Nets (provided by Polysack Plastic Industries, Israel) were established horizontally from July to October at 3 m height. Leaf chlorophyll content increased and the ratio Chl a/Chl b decreased as shading intensity increased, with the black nets giving the largest changes. Also, leaf photosynthesis, measured at the actual light intensity under the nets, decreased as shading intensity increased, with the red and black 70% having the lowest values. Fluorescence (Fv/Fm) was significantly lower in plants without shading (control) compared with plants under 70% shading (white, black or red). Nets retarded fruit development; thus, on August 10, the proportion of ripe fruit was 26.9% without shading, while less than 10% of the fruit were ripe under black 70%, black 50%, red 70% and red50%. On August 23, the separation between the controls and the most delayed fruit development (black 70%) was over 30%. In general, the various shading treatments increased fruit weight compared to the controls, but decreased fruit soluble solids, with the black 50 and 70% having the greatest impact. Thus it is clear that colored shade nets alter blueberry physiology and could be a valuable tool to displace peak harvest season in blueberries. INTRODUCTION Blueberries grow naturally in the understory. When plants are subject to open field conditions, they might be stressed due to excess radiation, temperature and moisture deficit. Colored shading nets have been investigated in ornamentals and fruit crops (OrenShamir et al., 2001; Shahak et al., 2004); in these crops, depending upon the degree of shading and color used, they have changed light quantity and quality received by plants, which has altered branching, shoot extension, time of harvest, fruit set and fruit quality. In this context, the use of shading nets could alleviate environmental stresses faced by blueberries, increase yields and delay harvest. MATERIALS AND METHODS The trial was conducted in Gobles, Michigan using a commercial 16-year-old field of ‘Elliott’ planted in a sandy loam soil at 3 x 1 m. A completely randomized design was used with 3 replications of each treatment. The treatments were applied to 4 rows of 6 plants each and data were collected from the 12 plants in the middle two rows. Combination of 3 colors of net (white, red and black) and 3 intensities (25, 50 and 75%) of shading nets (provided by Polysack Plastic Industries, Israel), plus control treatment (without net), generated 10 treatments (Fig. 1). The trial was established horizontally at 3.5 m height after fruit set (July 7, 2006) and removed at the onset of leaf drop.

Air Temperature and Illumination During Transportation Affect Quality of Mature Tomato Seedlings

Increasing numbers of greenhouse vegetable growers purchase transplants from specialized transplant propagators. Possible deterioration of transplants during transportation limits the market size as well as the potential sources of high-quality transplants. To determine the best conditions for transportation of seedlings, tomato (Lycopersicon esculentum Mill., cv. Durinta) seedlings with visible flower trusses were placed for 4 days inside growth chambers to evaluate the effects of short-term exposure to different air temperatures (6, 13, or a conventional transportation temperature of 19 °C) under darkness or illumination at 12 μmol·m–2·s–1 PPF. Plants were evaluated for visual quality, photosynthetic ability, growth, and fruit yield. Lower temperatures and illumination significantly maintained visual quality of the seedlings. Lower temperature maintained high photosynthetic ability of seedlings during the 4-day treatment. After transplanting in the greenhouse, a significant number of trusses exhibited flower abortion or delayed fruit development when seedlings were treated at 19 °C regardless of light intensity. Results suggested that 6 to 13 °C was the best transportation temperature for up to 4 days, which was later validated by an actual transportation trial between British Columbia and Arizona.

Application of 1-MCP for Quality Preservation of Tomato (Lycopersicon esculentum) Seedlings during Long-distance Transportation

Increasing numbers of vegetable growers purchase their seedlings from specialized transplant producers. However, early yield reduction due to abnormal first fruit truss development was often observed after long-distance transportation of seedlings. 1-Methylcyclopropene (1-MCP), an inhibitor of ethylene-mediated reactions, is widely used for postharvest management. If ethylene accumulated in trailers causes such abnormal first truss fruit development, application of 1-MCP to seedlings may prevent such problems. To test this hypothesis, `Durinta' tomato seedlings with visible flower buds were placed in chambers for 4 days under one of the following conditions: 1) conventional transportation air temperature of 18 °C without 1-MCP, 2) 18 °C with 1-MCP, 3) 12 °C without 1-MCP, and 4) nonstored control. The target initial 1-MCP concentration was 1 μmol·mol-1 inside the chamber, and the concentration was estimated to reach 0.2 μmol·mol-1 after 96 h. Three weeks after transplanting, 81.3% of first trusses on the plants treated at 18 °C without 1-MCP exhibited an abnormal, delayed fruit development. Both 1-MCP application and 12 °C air temperature successfully reduced the symptom to 4.7% and 3.1%, respectively; not significantly different from the nonstored control (1.6%). The average first truss yield was the lowest for 18 °C without 1-MCP (223 g per truss), followed by 18 °C with 1-MCP (582 g), and was the greatest (609–637 g) for 12 °C without 1-MCP or the control. Ethylene accumulation was the primary cause of the delayed fruit development causing yield reduction. Application of 1-MCP during transportation was shown to prevent such undesirable yield loss, although lowering temperature was the most effective under the present experimental conditions.

Can Cover Crop-based Systems Reduce Vegetable Crop Fertilizer Nitrogen Requirements in the Southeastern United States?

Poor water- and nutrient-holding capacity of sandy soils, combined with intense leaching rainfall events, may result in excessive N-fertilizers losses from vegetable production systems. Three cover cropping (CC) systems were used to assess supplemental N-fertilizer requirements for optimal yields of selected vegetable crops. Fertilizer N-rates were 0, 67, 133, 200, and 267; 0, 131, and 196; and 0, 84, 126,168, and 210 kg N/h for sweet corn (Zea mays var. rugosa), broccoli (Brassica oleracea), and watermelon (Citrullus lanatus), respectively. Crop rotations consisted of sunn hemp (Crotalaria juncea) in Fall 2003 followed by hairy vetch (Vicia villosa), and rye (Secale cereale) intercrop or a fallow. During Spring 2004, all plots were planted with sweet corn, followed by either cowpea (Vigna unguiculata) or pearl millet (Pennisetum glaucum), which preceded a winter broccoli crop. Hairy vetch and rye mix benefited from residual N from a previous SH crop. This cropping system provided a 5.4 Mg/ha yield increment for sweet corn receiving 67 kg N/ha compared to the conventional system. For the 133 N-rate, CC-based systems produced similar yields compared to conventional systems amended with 200 kg N/ha. Pearl millet accumulated 8.8 Mg/ha—but only 69 kg N/ha—and potential yields with this system were 16% lower compared to cowpea system. For a subsequent watermelon crop, trends were reversed, possibly due to a delay in mineralization for pearl millet. Because of its persistent growth after mowing, hairy vetch hampered initial growth and shading also delayed fruit development. Although CC may accumulate up to 131 kg N/ha actual N benefits, N-fertilizer benefits were only 67 kg N/ha, which may be related to a lack of synchronization between N release and actual crop demand.

Preliminary Observations on Particle Film and Mycorrhizae Use in Tomato Production

Kaolin cover sprays and mycorrhizal inoculation of tomatoes at transplanting were evaluated for their efficacy in improving tomato plant water status and agronomic performance in a supraoptimal, semiarid environment. Seven-week-old `Heatmaster' tomato plants (Lycopersicon esculentum Mill.) were transplanted with or without a vesicular-arbuscular mycorrhizal inoculant (Gomes intaradices Schenk &amp; Smith) on 19 Feb. 99 into a Raymondville clay loam soil in Weslaco, Texas (lat. 26°12′). One-half of the inoculated and one-half of the uninoculated plants were sprayed between 16 Mar. and 1 June with seven applications of the kaolin-based particle film “Surround.” The trickle-irrigated plots were 5.6 m2 in size and treatments replicated four times in a RCB design. Commercial cultural practices were followed, but no fungicides were used. Results indicated that mycorrhizal inoculation tended to accelerate fruit maturation and that particle film applications delayed fruit development relative to the control treatment. Mycorrhizal (only) treated plants had the highest yields at the second (of eight) harvests compared to the other treatments. There were no significant differences between treatments in leaf temperature, diffusive resistance, transpiration rate, water potential, and soil profile moisture, except between sampling dates. Fruit mineral nutrients, pigments, dry matter, average weight, total marketable and total season yields were not significantly affected by any treatment. When fruits were sectioned into proximal and distal halves, 10 out of the 14 nutrients measured, in addition to dry matter, and total carotenoids were higher in the distal end.

292 Effect of Pre-plant Application of VAM and Particle Film Applications on Tomato in a Supra-optimal, Semi-arid Environment

A reflectant particle film material, `Surround', which also has biocide properties, and mycorrhizal root inoculation of tomatoes at transplanting were evaluated for their efficacy in improving tomato plant water status and agronomic performance in a supra-optimal, semi-arid environment. Seven-week-old `Heatmaster' tomato plants (Lycopersicon esculentum Mill.) were transplanted with or without a VAM inoculant (Gomes intaradices, Schenk &amp; Smith) on 19 Feb. 1999 into a Raymondville clay loam soil in Weslaco, Texas (Lat. 26°12'). One-half of the inoculated and one-half of the uninoculated plants were sprayed between 16 Mar. and 1 June with seven applications of `Surround.' The trickle-irrigated plots were 5.6 m2 in size and treatments replicated four times in a RCB design. Recommended cultural practices were followed, but no fungicides were used. Results indicated that mycorrhizal treatment tended to accelerate fruit maturation and that particle film applications delayed fruit development relative to the control treatment. Mycorrhizal-treated plants had the highest yields at the second (of eight) harvest compared to the other treatments. There were no significant differences between treatments in leaf temperature, diffusive resistance, transpiration rate, water potential, and soil profile moisture, except between sampling dates. Fruit mineral nutrients, pigments, dry matter, average weight, total marketable and total season yields were not significantly effected by any treatment. When fruits were sectioned into proximal and distal halves, 10 out of 14 nutrients measured, in addition to dry matter, and total carotenoids were higher in the distal end.

Effect of GA3 Bloom Sprays on Fruit Set and Yield of Rabbiteye Blueberry

Field and growth chamber experiments, and grower trials, were conducted to determine the effects of GA3 sprays on yield and fruit quality of rabbiteye blueberry (Vaccinium ashei Reade) in northern Florida and southern Georgia. Multiple GA3 sprays at various stages of flower development increased fruit set and yield in field experiments (Florida) and grower trials (Georgia) when compared to controls. Nonpollinated rabbiteye flowers sprayed with GA3 had greater percent fruit set and delayed fruit development compared to hand pollination. Percent fruit set and average fruit weight were reduced at 21C night temperature when compared to 10C night temperature for both hand-pollinated and GA3-treated fruit. Overall, yields were increased by multiple applications of GA3 during bloom, but average fruit size was reduced and the fruit development period was lengthened.

Development time of parthenocarpic tomato (Lycopersicon esculentumMill.) fruits chemically and genetically induced

SummaryFruit development time was studied on the parthenocarpic cvs Severianin and 75/59 and on the non-parthenocarpic cvs 75/59 × Severianin and Severianin × 75/59 with three treatments: manual flower emasculation, synthetic auxin application and control; and four replications for each genotype. The plants were grown in an unheated polyethylene greenhouse in winter-spring and flowering lasted from the beginning of December to the end of February. The fruit development period (DP) decreased as the anthesis date advanced, associated with an increase in temperature. Cv 75/59 DP varied between 80 days (December) and 55 days (end of January), but was longer for Severianin (82 and 70 days). The DP of hybrids was intermediate between those of their parents. Low minimum temperatures delayed fruit development, particularly when they occurred in the first or second week after anthesis. The application of growth regulators reduced DP, both in parthenocarpic and non-parthenocarpic genotypes, although the reduction was greater in the latter. Moreover, it also reduced the number of fruits with seeds in non-parthenocarpic genotypes. When considering some integral of temperature measurement to correlate with fruit development as a whole, the temperature effect was less on fruit set using auxin than with untreated ones. For artificially set seedless fruits, there was a positive correlation between fruit weight and DP; such a correlation also exists for all the seeded fruits.

Cenizero Tree (Leguminosae: Pithecellobium saman) Delayed Fruit Development in Costa Rican Deciduous Forests

Pithecellobium saman (Leguminosae: cenízero) is one of several species of Costa Rican deciduous forest large trees that flower at the end of the dry season and then bear dormant tiny fruits through the following rainy season, to then abruptly enlarge and mature them during the first third of the next year's dry season. I postulate that this pattern of fruit development in P. saman minimizes the duration of exposure of immature seeds to parrot and insect seed predators, increases the tree's flexibility in the use of photosynthates accumulated for later fruit maturation, increases resource storage costs, and decreases the photosynthetic contribution that fruit and immature seeds can make to the parent tree's resource budget. These consequences imply that the fruiting phenology of P. saman, like that of other trees, is evolutionarily determined by its interactions with the habitat as well as by internal physiological factors.

The relationship between fruit growth and apical senescence in the G2 line of peas

In the G2 line of peas (Pisum sativum L.), senescence of the shoot apex (which precedes leaf senescence) only occurs in long days (LD) though flowering is independent of photoperiod. It has been suggested that the photoperiodic control of senescence in G2 is mediated through different rates of seed growth. In LD seed growth is more rapid than in short days (SD) and this places a greater nutrient drain on the plant. In addition, more flowers develop into fruits in LD than in SD: 32% of flower buds abort in SD while almost none abort in LD. Senescence is associated with early seed growth and does not occur in deflowered or deseeded plants. Seed development is completed in 30d in LD while it takes 40d in SD, though the seed weights are similar. The maximum rate of fresh-weight gain of all the growing seeds of eight fruits on a plant in SD (1,440 mg/d) does not reach the maximum rate of weight gain of a similar fruit complement in LD (1,720 mg/d). The appearance of senescence symptoms in the shoot apices of LD-grown G2 plants occurs, however, prior to the time of the greatest rate of seed-weight gain. In LD, four fruits with a combined maximum growth rate of 1,250 mg/d are sufficient to cause the appearance of senescence symptoms. This is a lower combined seed growth rate than in SD where senescence does not occur. The seeds in up to 12 fruits can be growing at any time in SD with a combined maximum seed-growth rate (1,660 mg/d), only slightly less than the maximum in LD, with no sign of senescence. It is concluded that the different rates of seed growth occasioned by different photoperiods bear no relation to senescence. However, photoperiod does alter the spatial relationship of the shoot apex and the filling fruits. In LD apical growth becomes slower as fruiting proceeds so that the distance between the filling fruits and the apex is decreased to only two nodes while in SD, because of the delayed fruit development compared to LD, the spatial separation between the fruits and the shoot apex is nine nodes. Even if the growth rate of the plant had remained constant in LD it is calculated that an equivalent fruit complement would still be located three nodes further from the apex in SD than in LD. This increased spatial separation of fruits and apex in SD compared to LD probably alters the source/sink distribution of photosynthate and leaf derived hormones so that larger amounts are available to the apex in SD than LD. Also any "senescence factor" exported from fruits is less likely to reach the apex in SD. In continuously deflorated plants of G2 the two uppermost expanded stipules enclose the apex in SD while in LD they open out. The effect is reversible. Thus photoperiod probably affects the apex and its growth, directly, i.e. independent of fruit development, and this is accentuated by the differing spatial relationships of the apex and fruits resulting from different fruit growth rates under the different photoperiodic conditions.