Photosynthate Partitioning Research Articles

Adaptive Responses of Biofortified Common Bean Lines to Acidic Soil and High Temperatures in the Colombian Amazon Region

One of the strategies to combat micronutrient malnutrition is by developing biofortified common bean lines (Phaseolus vulgaris L.) capable of tolerating different stress conditions. In this study, the adaptive responses of different biofortified bean lines grown under combined stress of acidic soil and high-temperatures were evaluated in the Colombian Amazon. A total of 247 common bean lines from the Mesoamerican gene pool were used to determine the adaptive response in terms of phenological, physiological, and agronomic behavior under combined stress conditions. The lines tested were obtained from different single crosses, double crosses, and backcrosses between different bean materials, of which 146 were obtained from F4 families with high iron (Fe) content in seed and 99 common bean lines from F5 families. Different bean lines had grain yields (GY) higher than 1400 kg ha−1 from the F5 (lines: 859, 805, 865, and 657) and F4 (lines: 2853 and 2796) families. The superior performance of these lines was related to a higher photosynthate partitioning that has allowed an increase in pod formation (pod partitioning index, PPI) from the canopy biomass (CB) and grain filling (pod harvest index, PHI; harvest index, HI), resulting in higher values of GY. Values of GY were correlated with CB (r = 0.36), PPI (r = 0.6), PHI (r = 0.68), and HI (r = 0.8, p < 0.001). This increase in agronomic performance is due to a greater allocation of energy to the photosynthetic machinery (ΦII) and its dissipation in the form of heat (ΦNPQ), with increases in the leaf temperature difference (LTD). Based on the results obtained, six biofortified lines of common bean (lines F5: 859, 805, 865, and 657; lines F4: 2853 and 2796) showed traits of tolerance to combined stress and can serve as progenitors to increase Fe and Zn concentration in the seeds of lines that tolerate the combined stress from acidic soil and high temperature in the Colombian Amazon region.

Role of Foliar Growth Retardants on Source Sink Relationship and Photosynthate Partitioning in Pigeonpea (Cajanus cajan L.) Genotypes

Role of Foliar Growth Retardants on Source Sink Relationship and Photosynthate Partitioning in Pigeonpea (Cajanus cajan L.) Genotypes

Form and contour: breeding and genetics of organ shape from wild relatives to modern vegetable crops.

Shape is a primary determinant of consumer preference for many horticultural crops and it is also associated with many aspects of marketing, harvest mechanics, and postharvest handling. Perceptions of quality and preference often map to specific shapes of fruits, tubers, leaves, flowers, roots, and other plant organs. As a result, humans have greatly expanded the palette of shapes available for horticultural crops, in many cases creating a series of market classes where particular shapes predominate. Crop wild relatives possess organs shaped by natural selection, while domesticated species possess organs shaped by human desires. Selection for visually-pleasing shapes in vegetable crops resulted from a number of opportunistic factors, including modification of supernumerary cambia, allelic variation at loci that control fundamental processes such as cell division, cell elongation, transposon-mediated variation, and partitioning of photosynthate. Genes that control cell division patterning may be universal shape regulators in horticultural crops, influencing the form of fruits, tubers, and grains in disparate species. Crop wild relatives are often considered less relevant for modern breeding efforts when it comes to characteristics such as shape, however this view may be unnecessarily limiting. Useful allelic variation in wild species may not have been examined or exploited with respect to shape modifications, and newly emergent information on key genes and proteins may provide additional opportunities to regulate the form and contour of vegetable crops.

Cotton Seed Size – What is the “Fuzz” all About?

Breeding efforts to improve lint yields in cotton may have shifted photosynthate partitioning to fibers during seed development resulting in a reduction in seed size in modern cotton cultivars. While the textile industry is the main consumer of cotton, changes in seed quality including size and composition could negatively impact other sectors of the agriculture industry that utilize cotton raw materials other than fiber. There is evidence of smaller cotton seeds impacting germination and seedling vigor as well as a reduction in oil content as seed size decreases. Moreover, downstream sectors of the cotton industry such as gins, crushers, and feedlots have been trying to draw attention to the consequences of having extremely small seeds to their operations, such as reduced ginning efficiency, seedcoat fragments, challenges in the delinting and decortication process, changes in meal nutrition, etc. This review focuses on the impacts of pursuing ever-increasing lint percent in modern cotton cultivars at the expense of seed size and attempts to highlight some of the less-known concerns of downstream cotton industry sectors.

Seasonal Changes in Photosynthate Partitioning in High Yielding Sweet Potato Varieties under Varied K Nutrition Levels

Background: Potassium is a major nutrient needed by the crops including tuber crops. It is essential for tuber initiation and bulking process. Varietal differences in potassium uptake and utilization in many crops were reported. As many varieties of sweet potato are released so far, studies on understanding the variations in potassium accumulation and its influence on tuber yield are essential. Methods: Field experiments were conducted during kharif and rabi seasons, 2021 with an objective to assess the seasonal influence and potassium nutrition [0 kg K2O/ha (K1), 50 kg K2O/ha (K2), 75 kg K2O/ha (K3) and 100 kg K2O/ha (K4)] on growth and tuber yield of five sweet potato varieties - four high yielding varieties (HYV) and one local variety [Bhu Krishna (V1), Sree Arun (V2), Sree Bhadra (V3), Bhu Sona (V4) and Kanjanghad Local (V5)]. There were 20 treatment combinations replicated thrice in a randomized block design. Result: Significantly higher tuber yield (17.01 t/ha) during kharif season was recorded by variety Bhu Sona. But during rabi season, Sree Arun was superior with a tuber yield of 23.92 t/ha. The potassium nutrition up to 75 kg K2O/ha increased the yield of sweet potato in rabi season. Interaction effect of two factors was also significant with respect to tuber yield, total chlorophyll content and tuber K content. Potassium Harvest Index (%) and Potassium Accumulation Value (g/plant) also significantly varied between varieties and K levels.

Cucumber STACHYOSE SYNTHASE is regulated by its cis-antisense RNA asCsSTS to balance source-sink carbon partitioning.

Photosynthate partitioning between source and sink is a key determinant of crop yield. In contrast to sucrose-transporting plants, cucumber (Cucumis sativus) plants mainly transport stachyose and stachyose synthase (CsSTS) synthesizes stachyose in the vasculature for loading. Therefore, CsSTS is considered a key regulator of carbon partitioning. We found that CsSTS expression and CsSTS enzyme activity were upregulated in the vasculature and downregulated in mesophyll tissues at fruiting. In situ hybridization and tissue enrichment experiments revealed that a cis-natural antisense noncoding transcript of CsSTS, named asCsSTS, is mainly expressed in mesophyll tissues. In vitro overexpression (OE), RNA interference (RNAi), and dual luciferase reporter experiments indicated that CsSTSs are negatively regulated by asCsSTS. Fluorescence in situ hybridization revealed that asCsSTS transcript localized in leaf cytoplasm, indicating that the regulation of CsSTS by asCsSTS is a posttranscriptional process. Further investigation revealed that this regulation occurred by reducing CsSTS transcript stability through a DICER-like protein-mediated pathway. Chemically induced OE and RNAi of asCsSTS led to promotion or inhibition, respectively, of assimilate export from leaves and altered fruit growth rates. Our results suggest that the regulation of CsSTSs between the mesophyll and vasculature reduces sugar storage in mesophyll tissue and promotes assimilate export from the leaf when the plant carries fruit.

Synchronised interaction of carbon and nitrogen provides drought tolerance in Cyamopsis tetragonoloba

Drought is a major adverse environmental factor that limits plant productivity. Concomitant assimilation of carbon (C) and nitrogen (N) in illuminated leaves requires the regulated partitioning of reductant and photosynthate to sustain the demands of amino acid and carbohydrate biosynthesis. The short-term exposure to drought and its responses of photosynthesis and photosynthate partitioning to N enrichment was studied in Cyamopsis tetragonoloba (L.) Taub (guar). Four contrasting varieties of guar, HG-563, RGC-986 (drought-tolerant) and RGC-471, Varsha (drought-sensitive) were subjected to 15 days water stress and leaf tissues were studied in order to contemplate the counter strategy engaged under drought conditions. In guar plants, sensors trigger a signalling cascade that activates numerous proteins to induce the expression of certain genes involved in carbon and nitrogen metabolism.The levels of glucose, starch, and Glutamate dehydrogenase (GDH), Aspartate aminotransferase (AspAT), isocitrate dehydrogenase (ICDH), Nitrate Reductase (NR), and Nitrite reductase (NiR) activities were determined biochemically during 15 days drought treatment, at three stages. Further, the carbon (oxidative phosphorylation and TCA cycle) - nitrogen metabolic pathway interaction was studied at the molecular level. The respiratory pathway genes were upregulated, while the nitrogen metabolic pathway genes were downregulated under all stages of drought in guar plants. The physiological, biochemical and molecular data suggests that the high rates of dark respiration was insufficient to provide extra carbon required to assist amino acid synthesis but rather sufficed by a rapid metamorphosis in the photosynthetic carbon partitioning to amino acid metabolism via the nitrogen metabolism. • Drought causes NADH DEHYDROGENASE gene to escalate dark respiration. • Nitrogen assimilation reduces under drought in leguminous Cyamopsis tetragonoloba. • Drought triggers protein kinase cascade signalling in guar plants. • Drought regulates nitrogen metabolic genes in guar. • Drought triggers increase in sugar content at the cost of amino acids.

Effect of foliar application of nutrients on growth and productivity of rabi maize (Zea mays L.)

Maize being the third important cereal crop after rice and wheat in terms of area and production plays an important role in food security. Like other cereal crops it utilizes greater amount of nutrients from soil. Still the farmers are not getting potential yield in summer maize. Foliar application of nutrients like nitrogen and potassium can enhance the yield and profit of farmers as it can accelerate the crop growth and help in partitioning of photosynthate in sink having a linear relationship of these nutrients with net assimilation ratio. Keeping in the view of the above points, this experiment was conducted at Bagusala Research Farm of Centurion University of Technology and Management, Paralakhemundi, Odisha using Randomized Block Design comprising three replications and nine treatments i.e., T1: Control, T2: Urea 0.5%, T3: Urea 1%, T4: K2SO4 0.5%, T5: K2SO4 1%, T6: Urea 0.5% + K2SO4 0.5%, T7: Urea 0.5% + K2SO4 1%, T8: Urea 1% -4 K2SO4 0.5% and Tg: Urea 1% + K2SO4 1%. All the foliar applications were done at tasseling stage of the crop. Crop growth parameters (plant height, dry matter accumulation/m2, leaf area index and stem girth), yield parameters (number of cobs/plant, number of grains/cob, cob length, cob girth and test weight) and yield (grain yield, stover yield and harvest index) were recorded and economics (net return and benefit cost ratio) were calculated. All the treatments significantly influenced the growth, yield parameters and yield. Among the treatments, foliar application of Urea 1% - K2SO4 1% performed the best achieving higher growth and grain yield (5.80 t/ha) and obtaining the highest net return (Rs. 62,597/-) and benefit cost ratio (1.37).

Waning advantages of CO2 enrichment on photosynthesis and productivity due to accelerated phase transition and source-sink imbalance in sweet pepper

CO2 concentration, which can be raised by CO2 enrichment, has been considered to affect photosynthetic physiology, morphology, and yield of crops in greenhouses. However, inconsistent influence of CO2 enrichment on crop productivity has been demonstrated owing to the complicated and dynamic interaction between physiological and morphological responses of crops. Therefore, integrative analysis on the systemic responses of crops to CO2 enrichment is required for clarifying the reasons for the inconsistency. The objective of this study was to analyze the effect of CO2 enrichment on the photosynthesis and yield of sweet pepper plants according to growth phase and to investigate how photosynthetic physiology and plant morphology contribute to the CO2 enrichment effect via functional structural plant model (FSPM), an integrative plant modeling tool. CO2 was enriched to sweet pepper plants with a daily average concentration of about 900 μmol mol−1. Growth, yield, and photosynthesis were periodically measured during the cultivation. The structural and photosynthetic properties obtained through 3D-phenotyping and gas-exchange measurement were applied to the 3D-framework for FSPM. The change in the CO2 enrichment efficiency for photosynthesis and the contribution of photosynthetic and morphological acclimation to CO2 enrichment effect were calculated. The overall influence of CO2 enrichment on the plants changed by growth stage mostly mediated by photosynthate source-sink balance. In early stages, CO2 enrichment accelerated the growth phase transition and increased the fruit yield through the increase in photosynthate partitioning to fruits. In later stages, however, the efficiency of CO2 enrichment on fruit yield gradually decreased due to the restricted leaf area expansion caused by excessive photosynthate partition to fruits. The systemic influence of CO2 enrichment on the plants including photosynthetic acclimation, structural acclimation, and fruit yield could be reasonably elucidated through the method used in this study. Thus, balancing the photosynthate source-sink balance in the early stages with appropriate cultivation practices could improve the long-term productivity of sweet pepper under CO2 enrichment.

The prokaryotic and fungal communities of oat rhizosphere responded contrastingly to different irrigation regimes at pre- and post-anthesis stages

The transition from the vegetative stage to reproductive stage of plants and variations in soil water regimes can alter the community feedbacks of rhizosphere microbiomes by affecting the partitioning of photosynthates to roots. However, little is known about how different rhizosphere microbiota respond to the growth stages of drought-resistant crops under different irrigation regimes. To address these issues, we investigated the effects of irrigation regimes on the rhizosphere prokaryotic and fungal communities at the pre- and post-anthesis stages of oats in a semi-arid region of northeastern China. The prokaryotic and fungal community traits of the oat rhizosphere were characterized by Illumina high-throughput sequencing. The results revealed that the prokaryotic diversity was primarily regulated by oat growth stage, while the fungal diversity was mainly increased by irrigation regimes. Similarly, all prokaryotic phyla responded significantly to oat growth stages rather than irrigation regimes, while the composition of the fungal taxa was largely regulated by irrigation regimes. Approximately 2–3-fold higher proportions of the predominating pathogenic Fusarium genus were identified under dryland farming conditions than under irrigation treatment. In addition, functional predictions suggested that the contrasting responsive traits of prokaryotes and fungi were attributed to their functional guilds, which were related to oat growth stages and soil water conditions. However, the properties of the prokaryotic networks mainly responded to irrigation regimes while the fungal networks were regulated by oat growth, implying distinct determination mechanisms for microbial diversity and community stability. Our results indicate that rhizosphere prokaryotic and fungal communities differentially responded to oat growth stages and soil water history, highlighting the significance of irrigation in manipulating rhizosphere microbes in semi-arid regions.

Water Use, Leaf Cooling and Carbon Assimilation Efficiency of Heat Resistant Common Beans Evaluated in Western Amazonia.

In our study, we analyzed 30years of climatological data revealing the bean production risks for Western Amazonia. Climatological profiling showed high daytime and nighttime temperatures combined with high relative humidity and low vapor pressure deficit. Our understanding of the target environment allows us to select trait combinations for reaching higher yields in Amazonian acid soils. Our research was conducted using 64 bean lines with different genetic backgrounds. In high temperatures, we identified three water use efficiency typologies in beans based on detailed data analysis on gasometric exchange. Profligate water spenders and not water conservative accessions showed leaf cooling, and effective photosynthate partitioning to seeds, and these attributes were found to be related to higher photosynthetic efficiency. Thus, water spenders and not savers were recognized as heat resistant in acid soil conditions in Western Amazonia. Genotypes such as BFS 10, SEN 52, SER 323, different SEFs (SEF 73, SEF 10, SEF 40, SEF 70), SCR 56, SMR 173, and SMN 99 presented less negative effects of heat stress on yield. These genotypes could be suitable as parental lines for improving dry seed production. The improved knowledge on water-use efficiency typologies can be used for bean crop improvement efforts as well as further studies aimed at a better understanding of the intrinsic mechanisms of heat resistance in legumes.

Adaptation of Interspecific Mesoamerican Common Bean Lines to Acid Soils and High Temperature in the Amazon Region of Colombia.

Knowledge of the physiological basis for improved genetic adaptation of common bean (Phaseolus vulgaris L.) lines to acid soils and high temperature conditions in the Amazon region of Colombia is limited. In this study, we evaluated the differences among 41 common bean lines in energy use, leaf cooling, photosynthate partitioning to pod formation and grain filling, and grain yield over two seasons under acid soil and high temperature stress in the Amazon region of Colombia. Common bean lines evaluated included medium and large seeded interspecific lines of Mesoamerican and Andean gene pools with different levels of adaptation to abiotic stress conditions and some lines are improved for iron and zinc (biofortified) concentration in seeds. We found three bean lines (GGR 147, SMG 21 and SMG 12) that were superior in their photosynthetic response, leaf cooling, photosynthate partitioning ability to pod formation and grain filling, resulting in grain yields exceeding 1900 kg ha−1 under acid soil and high temperature stress conditions. The superior photosynthetic performance was attributed to the efficient use of absorbed energy on the electron level in thylakoids, which is mainly oriented to a higher quantum yield of PSII (ΦII), lower energy dissipation in the form of heat (ΦNPQ), high linear electron flow (LEF) and high fraction of PSI centers in open state (PSIopen). We speculate that these photosynthetic and photosynthate partitioning responses of superior bean lines are part of the genetic adaptation to acidic soils and high temperature stress conditions. Among the evaluated bean lines, three lines (GGR 147, SMG 21 and SMG 12) combined the desirable attributes for genetic improvement of stress tolerance and biofortification. These lines can serve as parents to further improve traits (energy use efficiency and multiple stress resistance) that are important for bean production in the Amazon region.

Production and carbon allocation in clonal Eucalyptus plantations under different planting spacings

Wood productivity in plantation forests depends on successful choices of genetic materials and silvicultural practices. Wisely defining the intitial tree spacing according to edaphoclimatic conditions is important as spacing influences the amount of water, nutrients and light available for each tree. Resource availability, in turn, influences some important processes controlling wood production such as tree survival, CO2 uptake, and partitioning of photosynthates to stem wood and other tree compartments. Different genotypes may respond differently to tree spacing, due to possible differences in their canopy structure, physiology, and strategies for soil ressources acquisitions and carbon allocations. Our objective in this study was to investigate the interactive effects of genotype and tree spacing on wood production of fast-growing clonal eucalypt plantations in Southeastern Brazil. Tree growth, gross primary production (GPP) and partitioning of GPP to total belowground carbon flux (TBCF), wood and leaf production, and aboveground respiration were assessed in an experimental trial involving three commercial E. urophylla clones (AEC 0144, AEC 224 and COP 1404) planted at two spacings (3 m × 2 m; 3 m × 4 m). We hypotetized that (1) the most productive genotypes are those with both the highest GPP and the highest carbon partitioning to stem wood production; and (2) at closer spacing, leaf area index (LAI) and GPP are higher, but the partitioning to wood production is lower, and the belowground partitioning is higher, due to reduced soil water and nutrients availability per tree. Biomass and LAI were measured at ages 40 months (mid-rotation) and 52 months, and GPP, TBCF, wood production and leaf production were estimated between these two stand ages. Stem biomass and LAI were higher, for all clones, at the closer spacing (3 m × 2 m), as we could have expected since this spacing (corresponding to a stocking of 1667 tree ha−1) is the most commonly chosen in industrial eucalypt plantations in this region. Consistently with clonal ranking established in other studies, at spacing 3 m × 2 m clones were ranked as AEC 0144 > AEC 224 > COP 1404 for their wood production, but this ranking almost vanished at wide spacing. Our first hypothesis was supported by data: at spacing 3 m × 2 m the most productive clones (AEC 0144 > AEC 224 > COP 1404) were those with both the highest GPP (6.14 > 4.63 > 4.57 kg C m−2 year−1) and the highest carbon partitioning to wood production (0.33 > 0.29 > 0.26), although the differences between COP 1404 and AEC 224 were not significant (at P = 0.05). Our second hypothesis was only partially supported by data: wood biomass at age 40 months was higher at the closer spacing, but this positive effect of tight spacing seemed to decrease with stand age, as wood production and GPP measured between ages 40 and 52 months remained higher at the closer spacing only for clone AEC 0144. There was no consistent difference in the partitioning of GPP to wood production between the two spacings. The age-related decrease of the positive effect of high stockings may result from a faster depletion of deep soil water reserves in dense stands.

Shortening Internodes Near Ear: An Alternative to Raise Maize Yield

Plant growth retardants (mainly with active ingredient of ethephon) prevent maize (Zea mays L.) lodging as plant density increases, but frequently reduce grain yield if lodging is not a problem, in relation to application time. To explore the effects of ethephon application time on maize yield, literature published in the past 35 years concerning ethephon or ethephon-related plant growth retardant in maize were collected for meta-analysis. In addition, field experiments, including ethephon application time from 8- to 15-leaf stages, were conducted in 2018 and 2019. Exogenous application of ethephon decreased lodging as a function of reduced plant and ear height and enhanced bending strength and rind penetration resistance of basal stem internodes. Lodging rate was at the lowest level at the 8–10 leaf application of ethephon and then significantly increased with the delayed application. The degree of reduction of internode length was related to application time; ethephon application at n-leaf stage started to work at the n-2 internode and reduced the n internode length the most. Grain yield increased with the delayed application time and reached the highest level with application at the 14-leaf stage in 2019 (32.6%) compared with control treatment, mainly owing to the increased kernel/ear and kernel/m2. The internode length from the plant bottom to the top was negatively correlated with kernel/ear and kernel/m2, and the correlations were significant nearby and below the ear. Applying ethephon after the 13-leaf stage can avoid damaging floret number (potential kernel number per ear), at which time floret initiation has terminated. Besides, delayed ethephon application enabled stem growth to compete less with floret growth by reducing stem internode elongation during the critical period, and accelerated photosynthate partitioning from leaves to the ear, providing enough assimilate for kernel formation and growth. Taken together, delayed ethephon application (i.e., after 60% leaf age index) in combination with lodging resistant hybrids can further raise maize yield in the context of continuously increased plant densities.

Springtime Drought Shifts Carbon Partitioning of Recent Photosynthates in 10-Year Old Picea mariana Trees, Causing Restricted Canopy Development

Springtime bud-break and shoot development induces substantial carbon (C) costs in trees. Drought stress during shoot development can impede C uptake and translocation. This is therefore a channel through which water shortage can lead to restricted shoot expansion and physiological capacity, which in turn may impact annual canopy C uptake. We studied effects of drought and re-hydration on early season shoot development, C uptake and partitioning in five individual 10-year old Picea mariana [black spruce] trees to identify and quantify dynamics of key morphological/physiological processes. Trees were subjected to one of two treatments: (i) well-watered control or (ii) drought and rehydration. We monitored changes in morphological [shoot volume, leaf mass area (LMA)], biochemical [osmolality, non-structural carbohydrates (NSC)] and physiological [rates of respiration (Rd) and light-saturated photosynthesis (Asat)] processes during shoot development. Further, to study functional compartmentalization and use of new assimilates, we 13C-pulse labeled shoots at multiple development stages, and measured isotopic signatures of leaf respiration, NSC pools and structural biomass. Shoot water potential dropped to a minimum of −2.5 MPa in shoots on the droughted trees. Development of the photosynthetic apparatus was delayed, as shoots on well-watered trees broke-even 14 days prior to shoots from trees exposed to water deficit. Rd decreased with shoot maturation as growth respiration declined, and was lower in shoots exposed to drought. We found that shoot development was delayed by drought, and while rehydration resulted in recovery of Asat to similar levels as shoots on the well-watered trees, shoot volume remained lower. Water deficit during shoot expansion resulted in longer, yet more compact (i.e., with greater LMA) shoots with greater needle osmolality. The 12C:13C isotopic patterns indicated that internal C partitioning and use was dependent on foliar developmental and hydration status. Shoots on drought-stressed trees prioritized allocating newly fixed C to respiration over structural components. In conclusion, temporary water deficit delayed new shoot development and resulted in greater LMA in black spruce. Since evergreen species such as black spruce retain active foliage for multiple years, impacts of early season drought on net primary productivity could be carried forward into subsequent years.

Photoperiod-dependent transcriptional modifications in key metabolic pathways in Coffea arabica.

Photoperiod length induces in temperate plants major changes in growth rates, morphology and metabolism with, for example, modifications in the partitioning of photosynthates to avoid starvation at the end of long nights. However, this has never been studied for a tropical perennial species adapted to grow in a natural photoperiod close to 12 h/12 h all year long.We grew Coffea arabica L., an understorey perennial evergreen tropical species in its natural 12 h/12 h and in a short 8 h/16 h photoperiod, and we investigated its responses at the physiological, metabolic and transcriptomic levels. The expression pattern of rhythmic genes, including core clock genes, was affected by changes in photoperiod. Overall, we identified 2859 rhythmic genes, of which 89% were also rhythmic in Arabidopsis thaliana L. Under short-days, plant growth was reduced, and leaves were thinner with lower chlorophyll content. In addition, secondary metabolism was also affected with chlorogenic acid and epicatechin levels decreasing, and in agreement, the genes involved in lignin synthesis were overexpressed and those involved in the flavanol pathway were underexpressed.Our results show that the 8 h/16 h photoperiod induces drastic changes in morphology, metabolites and gene expression, and the responses for gene expression are similar to those observed in the temperate annual A. thaliana species.Short photoperiod induces drastic changes in gene expression, metabolites and leaf structure, some of these responses being similar to those observed in A. thaliana.

Genotypic variance in 13C-photosynthate partitioning and within-plant boll distribution in cotton

BackgroundPhotosynthate partitioning and within-plant boll distribution play an important role in yield formation of cotton; however, if and how they interact to mediate yield remains unclear. The objective of this study was to investigate the genotypic variance in photosynthate partitioning and within-plant boll distribution, with a focus on their interactions with regard to yield and yield components. A field experiment was conducted in the Yellow River region in China in 2017 and 2018 using a randomized complete block design with three replicates. Photosynthate partitioning of three commercial cultivars (DP 99B, Lumianyan 21 and Jimian 169), varying in yield potential, to different organs (including bolls) at early flowering, peak flowering, and peak boll-setting stages, as well as within-plant boll distribution at harvest, and their effects on yield formation were examined.ResultsLint yield of Jimian 169 was the highest, followed by Lumianyan 21 and DP 99B. Similar differences were observed in the number of inner bolls and boll weight among the three cultivars. J169 partitioned significantly more photosynthate to the fruit and fiber than Lumianyan 21 and DP 99B and allocated over 80% of assimilates to the inner bolls. Additionally, Lumianyan 21 allocated a higher proportion of photosynthate to bolls and fiber, with 12.5%–17.6% more assimilates observed in the inner bolls, than DP 99B.ConclusionsGenotypic variance in lint yield can be attributed to differences in the number of inner bolls and boll weight, which are affected by photosynthate partitioning. Therefore, the partitioning of photosynthate to fiber and inner bolls can be used as an important reference for cotton breeding and cultivation.

Improved Yield and Photosynthate Partitioning in AVP1 Expressing Wheat (Triticum aestivum) Plants.

A fundamental factor to improve crop productivity involves the optimization of reduced carbon translocation from source to sink tissues. Here, we present data consistent with the positive effect that the expression of the Arabidopsis thaliana H+-PPase (AVP1) has on reduced carbon partitioning and yield increases in wheat. Immunohistochemical localization of H+-PPases (TaVP) in spring wheat Bobwhite L. revealed the presence of this conserved enzyme in wheat vasculature and sink tissues. Of note, immunogold imaging showed a plasma membrane localization of TaVP in sieve element- companion cell complexes of Bobwhite source leaves. These data together with the distribution patterns of a fluorescent tracer and [U14C]-sucrose are consistent with an apoplasmic phloem-loading model in wheat. Interestingly, 14C-labeling experiments provided evidence for enhanced carbon partitioning between shoots and roots, and between flag leaves and milk stage kernels in AVP1 expressing Bobwhite lines. In keeping, there is a significant yield improvement triggered by the expression of AVP1 in these lines. Green house and field grown transgenic wheat expressing AVP1 also produced higher grain yield and number of seeds per plant, and exhibited an increase in root biomass when compared to null segregants. Another agriculturally desirable phenotype showed by AVP1 Bobwhite plants is a robust establishment of seedlings.

Starch: A Flexible, Adaptable Carbon Store Coupled to Plant Growth.

Research in the past decade has uncovered new and surprising information about the pathways of starch synthesis and degradation. This includes the discovery of previously unsuspected protein families required both for processes and for the long-sought mechanism of initiation of starch granules. There is also growing recognition of the central role of leaf starch turnover in making carbon available for growth across the day-night cycle. Sophisticated systems-level control mechanisms involving the circadian clock set rates of nighttime starch mobilization that maintain a steady supply of carbon until dawn and modulate partitioning of photosynthate into starch in the light, optimizing the fraction of assimilated carbon that can be used for growth. These discoveries also uncover complexities: Results from experiments with Arabidopsis leaves in conventional controlled environments are not necessarily applicable to other organs or species or to growth in natural, fluctuating environments.

Seasonal irrigation affects the partitioning of new photosynthate carbon in soil

Long-term irrigation of temperate pastures has been reported to either increase or decrease soil organic carbon (SOC) stocks when compared with dryland systems. Understanding the short-term effects of irrigation on the fixation and partitioning of carbon (C) to plant and soil components may be important to explaining the observed differences. Continuous 13CO2 pulse labelling of ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) planted mesocosms was used to quantify the net accumulation and partitioning of new photosynthate C to above- and below-ground components of the plant-soil system, including soil particle size fractions: > 250 μm, 53–250 μm, 20–53 μm, 5–20 μm and <5 μm, under simulated irrigation and dryland conditions.After the 13CO2 labelling, irrigation increased the quantity of 13C partitioned into herbage by 16%, while reducing the quantity partitioned into roots in the 15–25 cm soil depth by 35%. However, less new photosynthate C was observed in rhizosphere soil (0–15 cm depth), while more new photosynthate C was partitioned into the 53–250 μm and <5 μm soil fractions under irrigation. Despite these differences, the net amount of new photosynthate C in the whole soil (0–25 cm depth) was similar between treatments (2511 kg new C ha−1 dryland and 2509 kg new C ha−1 irrigated). Therefore, irrigation did not increase the net amount of new photosynthate C in the soil despite increased above-ground pasture productivity.Based on our results, we hypothesise that the recently reported losses of SOC from irrigated pastures may be driven by faster turnover of root-derived C, which may explain the increase in photosynthate C in the fine POM soil size fraction (53–250 μm), rather than a reduction in photosynthate C inputs to the soil.