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The regulation of sugar and organic acid metabolism during fruit development has a major effect on high-quality fruit production. The reduction of leaf area is a common feature in plant growth, induced by abiotic and biotic stresses and disturbing source/sink ratio, thus impacting fruit quality. Here, we induced carbohydrate limitation by partial leaf defoliation at the beginning of the second stage of mandarin development (before the citrate peak). Resulting changes were monitored in the short-term (48 h and 1 week) and long-term (7 weeks) after the defoliation. Short-term response to early defoliation implied metabolic settings to re-feed TCA for sustaining respiration rate. These features involved (i) vacuolar sucrose degradation (high acid invertase activity and mRNA expression level) and enhanced glycolytic flux (high ATP-phosphofructokinase activity), (ii) malic and citric acid utilization (increased phosphoenolpyruvate kinase and NADP-Isocitrate dehydrogenase) associated with vacuolar citric acid release (high mRNA expression of the transporter CsCit1) and (iii) stimulation of GABA shunt pathway (low GABA content and increased mRNA expression of succinate semialdehyde dehydrogenase). A steady-state proline level was found in ED fruits although an increase in P5CS mRNA expression level. These results contribute to a better knowledge of the molecular basis of the relationship between defoliation and sugar and organic acid metabolism in mandarin fruit.

Terminal heat stress has detrimental effect on the growth and yield of wheat. Very limited information is available on heat stress-associated active proteins (SAAPs) in wheat. Here, we have identified 159 protein groups with 4271 SAAPs in control (22 ± 3 °C) and HS-treated (38 °C, 2 h) wheat cvs. HD2985 and HD2329 using iTRAQ. We identified 3600 proteins to be upregulated and 5825 proteins to be downregulated in both the wheat cvs. under HS. We observed 60.3% of the common SAAPs showing upregulation in HD2985 (thermotolerant) and downregulation in HD2329 (thermosusceptible) under HS. GO analysis showed proton transport (molecular), photosynthesis (biological), and ATP binding (cellular) to be most altered under HS. Most of the SAAPs identified were observed to be chloroplast localized and involved in photosynthesis. Carboxylase enzyme was observed most abundant active enzymes in wheat under HS. An increase in the degradative isoenzymes (α/β-amylases) was observed, as compared to biosynthesis enzymes (ADP-glucophosphorylase, soluble starch synthase, etc.) under HS. Transcript profiling showed very high relative fold expression of HSP17, CDPK, Cu/Zn SOD, whereas downregulation of AGPase, SSS under HS. The identified SAAPs can be used for targeted protein-based precision wheat-breeding program for the development of 'climate-smart' wheat. [ABSTRACT FROM AUTHOR]

Aim: The present study was conducted in grapevines to evaluate the influence of source/sink disturbance on reserve restoration in the entire plant (trunk, roots) and the consequences on reproduction, yield, sugar yield, potential alcohol content and total acidity over four successive years of treatment. Methods and results: At véraison, either total defoliation or total fruit removal was performed on Chardonnay plants grown in vineyards. The impact was measured each year on reproductive parameters and after four years on both plant weight and carbohydrate content. Defoliation induced an alteration in carbohydrate distribution in the entire plant, as revealed by decrease of starch content and parallel increase of soluble sugar content. These modifications affected the number of inflorescences/clusters per plant the year after. By contrast, fruit removal resulted in a significant increase of carbohydrate reserves in the whole plant, although the efficiency of sexual reproduction was not improved the year after. Conclusion: Results confirm the close correlation between carbohydrate reserves and the efficiency of sexual reproduction. Moreover, grapevine is able to adapt the number of both inflorescences and flowers according to the amount of available carbohydrate reserves in perennial organs. Significance and impact of the study: The quality of the crop is affected by defoliation, as shown by the decrease in yield and sugar yield. However, the impact on potential alcohol content and total acidity was less pronounced.

High grain nitrogen (N) concentration in crops may require to translocate more N from the vegetative tissues, cause faster plant senescence, alter sink-source balance during grain filling, and ultimately lower grain yield. Previous studies have shown that indica hybrid rice (IH) have shorter grain-filling period, and lower biomass and grain yield, compared with japonica/indica hybrid rice (JIH) and japonica conventional inbred rice (JC) in China. We hypothesise that these are caused by early senescence and poor sink-source balance after heading in IH as a result of its high grain N concentration. In this study, two JIH, two JC, and two IH varieties were grown in 2013 and 2014 at Ningbo, and in 2015 and 2016 at Yangzhou, China, and the observed dynamics of grain and crop biomass were fitted to mathematical equations to quantify sink-source relationships during grain filling. Compared with JC and IH varieties, JIH varieties showed higher sink growth and source capacity and 7.5–21.6% higher grain yield across years and sites. In JIH and JC genotypes, total source during grain filling was higher than the total sink value, whereas opposite was observed for IH genotypes. Source-sink difference, source/sink ratio, and grain-filling duration all negatively (P < 0.01) correlated with grain N concentration at maturity. Compared with JIH and JC, IH accumulated more N in grains and translocated more N from leaf during the period from heading to maturity. We conclude that early senescence and poor sink-source balance after heading of IH was linked to its high grain N concentration, and sink-source relationships during rice grain filling were associated with grain N concentration. Further breeding and cultivation programmes should aim at improving sink-related traits in JIH and JC genotypes, whereas for IH varieties, whether yield was set by sink size or by any limited availability of pre-heading reserves remains to be further examined. [ABSTRACT FROM AUTHOR]

The regulation of sugar and organic acid metabolism during fruit development has a major effect on high-quality fruit production. The reduction of leaf area is a common feature in plant growth, induced by abiotic and biotic stresses and disturbing source/sink ratio, thus impacting fruit quality. Here, we induced carbohydrate limitation by partial leaf defoliation at the beginning of the second stage of mandarin development (before the citrate peak). Resulting changes were monitored in the short-term (48 h and 1 week) and long-term (7 weeks) after the defoliation. Short-term response to early defoliation implied metabolic settings to re-feed TCA for sustaining respiration rate. These features involved (i) vacuolar sucrose degradation (high acid invertase activity and mRNA expression level) and enhanced glycolytic flux (high ATP-phosphofructokinase activity), (ii) malic and citric acid utilization (increased phosphoenolpyruvate kinase and NADP-Isocitrate dehydrogenase) associated with vacuolar citric acid release (high mRNA expression of the transporter CsCit1) and (iii) stimulation of GABA shunt pathway (low GABA content and increased mRNA expression of succinate semialdehyde dehydrogenase). A steady-state proline level was found in ED fruits although an increase in P5CS mRNA expression level. These results contribute to a better knowledge of the molecular basis of the relationship between defoliation and sugar and organic acid metabolism in mandarin fruit., Competing Interests: The authors declare no competing interests., (© 2023 The Authors. Published by Elsevier Ltd.)

A large proportion of soybean flowers abort during development. Pod set is significantly affected by the availability of assimilate and cytokinin in the flowers, but their synergistic effects on pod set remain unclear. The objective of this study was to examine whether pod set at specific nodes of a plant is enhanced by increasing the source-sink ratio and applying cytokinin to the nodes. The source-sink ratio was manipulated by removing floral buds excluding the specific nodes. As the ratio increased, the number of pods per node of control plants increased curvilinearly, reaching a plateau at high source/sink ratios. By contrast, in the cytokinin-applied plants, the number of pods per node increased without the plateau with increasing source/sink ratio, either by increasing the number of flowers or by increasing the pod-set percentage depending on the year. The results indicated that cytokinin plays a promotive role in increasing pod number in the plants with high levels of assimilate availability.

Understanding the role of branch architecture in carbon production and allocation is essential to gain more insight into the complex process of assimilate partitioning in fruit trees. This mini review reports on the current knowledge of the role of branch architecture in carbohydrate production and partitioning in apple. The first-order carrier branch of apple illustrates the complexity of branch structure emerging from bud activity events and encountered in many fruit trees. Branch architecture influences carbon production by determining leaf exposure to light and by affecting leaf internal characteristics related to leaf photosynthetic capacity. The dynamics of assimilate partitioning between branch organs depends on the stage of development of sources and sinks. The sink strength of various branch organs and their relative positioning on the branch also affect partitioning. Vascular connections between branch organs determine major pathways for branch assimilate transport. We propose directions for employing a modelling approach to further elucidate the role of branch architecture on assimilate partitioning.

Understanding the role of branch architecture in carbon production and allocation is essential to gain more insight into the complex process of assimilate partitioning in fruit trees. This mini review reports on the current knowledge of the role of branch architecture in carbohydrate production and partitioning in apple. The first-order carrier branch of apple illustrates the complexity of branch structure emerging from bud activity events and encountered in many fruit trees. Branch architecture influences carbon production by determining leaf exposure to light and by affecting leaf internal characteristics related to leaf photosynthetic capacity. The dynamics of assimilate partitioning between branch organs depends on the stage of development of sources and sinks. The sink strength of various branch organs and their relative positioning on the branch also affect partitioning. Vascular connections between branch organs determine major pathways for branch assimilate transport. We propose directions for employing a modelling approach to further elucidate the role of branch architecture on assimilate partitioning. [ABSTRACT FROM AUTHOR]

Source/sink ratios are known to be one of the main determinants of oil palm growth and development. A long-term experiment (9 years) was conducted in Indonesia on mature oil palms subjected to continuous bunch ablation and partial defoliation treatments to artificially modify source/sink ratios. During the experiment, all harvested bunches were dissected and phenological measurements were carried out to analyse the effect of source/sink ratios on yield components explaining variations in bunch number, the number of fruits per bunch and oil dry weight per fruit. An integrative variable (supply/ demand ratio) describing the ratio between the assimilate supply from sources and the growing organ demand for carbohydrate was computed for each plant on a daily basis from observations of the number of developing organs and their sink strength, and of climate variables. Defoliation and bunch ablation affected the bunch number and the fruit number per bunch. Variations in bunch number per month were mainly due to variations in the fraction of aborted inflorescence and in the ratio between female and male inflorescences. Under fluctuating trophic conditions, variations in fruit number per bunch resulted both from changes in fruit-set and in the number of branches (rachillae) per inflorescence. For defoliated plants, the decrease in the number of developing reproductive sinks appeared to be sufficient to maintain fruit weight and oil concentration at the control level, without any major decrease in the concentration of non-structural carbohydrate reserves. Computation of the supply/demand ratio revealed that each yield component had a specific phase of sensitivity to supply/demand ratios during inflorescence development. Establishing quantitative relationships between supply/demand ratios, competition and yield components is the first step towards a functional model for oil palm. [ABSTRACT FROM AUTHOR]

It is recognized that soybean remobilizes carbohydrates and protein compounds from vegetative to reproductive organs during the last half of the seed filling period. However, reports quantifying how much of final yield is constituted by these remobilized materials under field conditions are lacking. The objective of the current study was to determine the contribution of remobilized total dry matter (TDM) to final yield under field conditions. Using five field studies conducted from 1987 through 1995 near Baton Rouge, LA (30°N latitude), % remobilized yield was determined by using crop growth rate during the final half of seed filling (CGR[R6.2-R7]) to calculate how much of the final 50% of seed weight was contributed by remobilized TDM. The % remobilized yield was then calculated as 100 x (remobilized seed TDM/yield). Results indicated that % remobilized yield varied from 15% to 30% and tended to increase as growing conditions improved and plant size increased. Percent remobilized yield also increased when source/sink ratio declined during the rapid seed filling period (R6-R7). In conclusion, a substantial portion of final yield is derived from remobilized TDM. [ABSTRACT FROM PUBLISHER]

Abstract: Nitrogen supply can improve crop growth and yield. An over-use of nitrogen fertilizer in greenhouse crop productions, however, causes many environmental problems. The aim of this study was to quantify the effects of nitrogen on fruit growth and yield so as to facilitate the optimization of nitrogen management for cucumber (Cucumis sativus) crop in greenhouses. Four experiments with different levels of nitrogen treatments, substrates and planting dates on cucumber (cv. Deltastar) were conducted in greenhouses located at Shanghai during 2005 and 2007. Using data of one experiment, seasonal time courses of leaf nitrogen content (N L), leaf area per plant (LA), and the number of fruits growing per plant (n FG), as well as time course of the length of individual fruit growing on the plant (L F(i)) under different levels of nitrogen supply conditions were, respectively, determined as functions of a photo-thermal index (PTI). The impact of N L on LA was determined by curve fitting to the experimental data. The source/sink ratio (LA/n FG), an indicative of the source size per fruit, was then derived from the seasonal time courses of LA and n FG. The impact of N L on L F(i) was indirectly quantified by the relationship between source/sink ratio (LA/n FG) and the elongation rate of individual fruit (R FL(i)). Both the harvest date and fresh weight (W F(i)) of individual fruit growing at different node, and number of harvested fruits (n FH) were then calculated as functions of the fruit length. These quantitative relationships were assembled to form a model for predicting the effects of nitrogen on fruit growth and yield (fruit fresh weight per plant). Independent data from other experiments were used to validate the model. Our model gives satisfactory predictions of cucumber fruit growth and yield under different levels of nitrogen supply and growing season conditions. The coefficient of determination (r 2) and the relative root mean squared error (rRMSE) between the predicted and measured values are, respectively, 0.92 and 0.22 (r 2, rRMSE) for leaf area per plant, 0.90 and 0.24 for the number of fruits growing on the plant, 0.91 and 0.22, 0.90 and 0.23, and 0.92 and 0.21, respectively, for the length, harvest date and fresh weight of individual fruit growing on the plant, 0.94 and 0.20 for yield. The model may be used for the optimization of nitrogen management for cucumber production in greenhouses. Further model calibration and test would be needed when applying this model to a wider range of conditions. [Copyright &y& Elsevier]

Abstract: Final kernel weight (KW) is closely related to maximum kernel volume (KV) and maximum kernel water content (KWC). It is not clear, however, how changes in the reproductive sink capacity, assimilate availability during grain filling and physical restriction to kernel expansion affect the relationship between KW and KWC or between KW and KV. Three experiments were conducted at Balcarce, Argentina and Ames, USA. Defoliation, thinning, plant density, restricted pollination and volume restriction treatments were imposed to manipulate KV, sink and source capacity. KW varied from 111 to 436mg across all hybrid–treatments combinations and was related to the source/sink ratio during grain filling (r 2 =0.85). Treatment variation in KW was related primarily to changes in kernel growth rate, except for the complete defoliated treatment, which also shortened the duration of grain filling. KW was correlated with maximum KWC (r 2 =0.77, p <0.001) and with maximum KV (r 2 =0.91, p <0.001). The developmental patterns for KW, KWC and KV during grain filling were not affected by the source/sink manipulations, except for severe defoliation. In the latter case, maximum KWC was not a good estimate of final KW. KV, however, was sensitive to reductions in carbohydrate supply during grain filling and was closely correlated to KW. Physical restriction to kernel expansion reduced kernel weight 13% relative to its control (p <0.01). But restricting kernel expansion did not alter the general relationships between KW and KWC or between KW and KV, because kernel density was not affected. [Copyright &y& Elsevier]

ABSTRACT With the advent of black sigatoka in commercial banana crops in the “Vale do Ribeira” region, state of São Paulo, the monitoring the severity and chemical control of the disease in susceptible varieties have become more frequent in order to avoid leaf loss. This study simulated the effect of defoliation caused by the disease on the yield and quality of ‘Prata Comum’ banana fruits, depending on the formation period and fruit position in the bunch. The experimental design was completely randomized in a 2 x11 factorial scheme (period of bunch formation x number of leaves at flowering), 6-16 leaves at flowering in two periods of bunch formation with six replicates. In Period 1, flowering occurred at 04/15/13 and in Period 2 at 01/07/14, although in Period 1, bunch mass was higher and in Period 2, higher average maximum and minimum daily temperatures, precipitation and radiation were observed. Regardless of formation period, the number of leaves at flowering affected bunch mass, which ranged from 18 to 23 kg plant-1. Defoliation affected the size of fruits of hand 1 and last hand of the bunch, but not the variability in fruit size due to the position the fruit occupies in the bunch and physicochemical characteristics.

ABSTRACT: Defoliation caused by Black Sigatoka in yield and quality of banana 'Nanica' was stimulated in this study. A completely randomized 2x8 factorial design with six repetitions was used, in which period of bunch formation and number of leaves at flowering were established as factors. Plants for defoliation were selected on 04/05/2013 (Period 1), and on 07/01/2014 (Period 2). Six to to 13 leaves remained per plant by removing those with more than 50% of blade with injury or senescence. More appropriate climatic conditions before and after flowering, promoted greater mass accumulation in the bunch in Period 2. The increased number of leaves at flowering increased the length of the fruit and the mass of 4th hand, as well as the bunch mass and postharvest period. Defoliation is suggested only for non-functional leaves as well as the maintenance of at least 10 leaves per plant, independent of the period of bunch formation.