Translocation Of Photoassimilates Research Articles

Halotolerant Microorganism-Based Soil Conditioner Application Improved the Soil Properties, Yield, Quality and Starch Characteristics of Hybrid Rice under Higher Saline Conditions.

Soil salinity represents a significant factor affecting agricultural productivity and crop quality. The present study was conducted to investigate the effects of soil conditioner (SC) comprising halotolerant microorganisms on the soil fertility, yield, rice quality, and the physicochemical and structural properties of starch in hybrid rice under saline conditions. The experimental treatments were composed of two high-quality hybrid rice varieties, i.e., 'Y Liangyou 957' (YLY957) and Jing Liangyou 534 (JLY534), and two soil amendment treatments, i.e., the application of SC at control levels and 2250 kg hm-2, or 'CK and SC', respectively. The crop was subjected to a mixture of fresh and sea water (EC 11 dS/m). The results demonstrated that the application of SC significantly enhanced the rice yield under salt stress conditions owing to an increase in the number of grains per panicle. Furthermore, SC was found to be effective in improving the organic matter and soil nutrient content. Furthermore, the application of SC resulted in an improvement in antioxidant defense, higher leaf SPAD values, and greater crop biomass, as well as the translocation of photo-assimilates at the heading stage. The application of SC not only improved the milling and appearance quality but also enhanced the taste value of rice by increasing the amylose and reducing the protein content. Furthermore, the application of SC also decreased the indentations on the surfaces of starch granules and cracks on the edges of the granules. The rice varieties subjected to SC exhibited excellent pasting properties, characterized by reduced proportions of amylopectin short chains and a lower gelatinization temperature and enthalpy of gelatinization. Overall, these findings serve to reinforce the efficacy of soil conditioner as a valuable tool to improve rice productivity and sustainability with improved rice grain quality under saline conditions.

Drought stress reduces the photosynthetic source of subtending leaves and the transit sink function of podshells, leading to reduced seed weight in soybean plants.

Drought stress is the key factor limiting soybean yield potential. Soybean seed formation involves a coordinated "subtending leaf-podshell-seed" process, but little is known about the assimilation and transport of photoassimilates in subtending leaves, podshells and seeds or their relationships with soybean seed formation under drought stress. To address these research gaps, two-year experiments with two soybean cultivars, Wandou 37 (drought tolerant) and Zhonghuang 13 (drought sensitive), were conducted under three soil water content (SWC) conditions in 2020 and 2021 based on the responses of their yield to drought. We analyzed the photosynthetic assimilation and translocation of photoassimilates in subtending leaves, podshells and seeds by stable isotope labeling. Compared with those under 75% SWC, 60% SWC and 45% SWC significantly decreased the Wandou 37 seed weight by 19.4% and 37.5%, respectively, and that of Zhonghuang 13 by 26.9% and 48.6%, respectively. Compared with those under 75% SWC, drought stress decreased the net photosynthetic rate and the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SuSy), which in turn decreased the photosynthetic capacity of the subtending leaves. The podshells ensure the input of photoassimilates by increasing the SuSy activity, but the weakened source-sink relationship between podshells and seeds under drought stress leads to a decrease in the translocation of assimilates from podshells to seeds. The lack of assimilates under drought stress is an important factor restricting the development of soybean seeds. We conclude that the decrease in seed weight was caused by the decrease in the photosynthetic capacity of the subtending leaves and the decrease in the overall availability of photoassimilates; moreover, by a decrease in the translocation of assimilates from podshells to seeds.

Effects of Fulvic Acid on Growth and Nitrogen Utilization Efficiency in M9T337 Seedlings

Both fulvic acid (FA) and nitrogen (N) play important roles in agricultural production in China. Plants typically show a higher nitrogen utilization efficiency (NUE) under FA application. However, the role of FA application in apple growth and NUE remains unclear. A hydroponic culture experiment was performed, and M9T337 seedlings (a dwarf apple rootstock) were used as the experimental subjects. The biomass, photosynthesis, accumulation, and distribution of photosynthates, N absorption and assimilation, and relative gene expression in the seedlings were examined after treatment with five different concentrations of FA (0, 60, 120, 180, and 240 mg·L−1, represented by CK, FA1, FA2, FA3, FA4, respectively). The results showed that the seedling dry weight and 15NUE were enhanced by FA, and both were highest under the FA2 (the concentration of fulvic acid is 120 mg·L−1) treatment. Further analysis revealed that under the FA2 treatment, the root morphology was optimized, and the root activity was relatively high. Compared with CK (control, the concentration of fulvic acid is 0 mg·L−1), the FA2 treatment strengthened photosynthesis, elevated the key enzyme activities related to C metabolism, upregulated the gene expression of sugar transport proteins, and increased the root sorbitol and sucrose contents, which suggested that the FA2 treatment optimally affected the root growth and N absorption because it enhanced photosynthate synthesis and the leaf-to-root translocation of photoassimilates. The seedlings in the FA2 treatment group also showed a significantly higher NO3− influx rate and NRT (nitrate transporter) gene expression in the roots. Moreover, relatively high N metabolism-related enzyme activities in the leaves and roots were also observed under the FA2 treatment. The isotope labeling results showed that the optimal FA2 supply not only promoted seedling 15N absorption but also optimized the distribution of C and N in the seedlings. These results suggested that an optimal FA supply (120 mg·L−1) enhanced seedling NUE by strengthening photoassimilate synthesis and transport from leaves to roots, regulating N absorption, assimilation, and distribution.

Potassium transporter OsHAK18 mediates potassium and sodium circulation and sugar translocation in rice.

High-affinity potassium (K+) transporter (HAK)/K+ uptake permease (KUP)/K+ transporter (KT) have been identified in all genome-sequenced terrestrial plants. They play an important role in K+ acquisition and translocation and in enhancing salt tolerance. Here, we report that plasma membrane-located OsHAK18 functions in K+ and sodium (Na+) circulation and sugar translocation in rice (Oryza sativa). OsHAK18 was expressed mainly, though not exclusively, in vascular tissues and particularly in the phloem. Knockout (KO) of OsHAK18 reduced K+ concentration in phloem sap and roots but increased K+ accumulation in the shoot of both 'Nipponbare' and 'Zhonghua11' cultivars, while overexpression (OX) of OsHAK18 driven by its endogenous promoter increased K+ concentration in phloem sap and roots and promoted Na+ retrieval from the shoot to the root under salt stress. Split-root experimental analysis of rubidium (Rb+) uptake and circulation indicated that OsHAK18-OX promoted Rb+ translocation from the shoot to the root. In addition, OsHAK18-KO increased while OsHAK18-OX reduced soluble sugar content in the shoot and oppositely affected the sugar concentration in the phloem and its content in the root. Moreover, OsHAK18-OX dramatically increased grain yield and physiological K+ utilization efficiency. Our results suggest that-unlike other OsHAKs analyzed heretofore-OsHAK18 is critical for K+ and Na+ recirculation from the shoot to the root and enhances the source-to-sink translocation of photo-assimilates.

Cotton harvest aids promote the translocation of bur-stored photoassimilates to enhance single boll weight

The application of harvest aids is an important prerequisite for realizing cotton mechanical harvesting. It is necessary to clarify the impact of harvest aid application on photoassimilate translocation and partitioning in the cotton boll–leaf system to reduce the negative impacts of harvest aids on seed cotton yield. The objective of this study was to determine the effects of harvest aids on photoassimilate repartitioning in the cotton boll–leaf system and its relationship with boll weight formation in the late growth stage of cotton. The leaf photosynthetic rate decreased sharply 1 d after applying harvest aids, and was only 0.91–6.30 μmol m−2 s−1 3 d after spraying. In addition, the synthesis and transport of leaf photosynthates were rapidly restricted. The contribution rate of leaf photosynthates to boll weight under ethephon application was 0.52–1.97%, showing a positive contribution. The application of harvest aids significantly reduced the single boll weight by 0.21–0.58 g, and the fiber weight per boll and the cottonseed weight per boll were 1.59–1.81 g and 2.19–2.60 g, respectively. About 0.09–0.15 g of photoassimilates in the bur were repartitioned after harvest aid application, and the contribution to the boll weight was 4.47–10.33%. The probability of increasing the boll weight by increasing the photoassimilate translocation rate in the bur was 33.8–46.1%. When the bur weight decreased by 0.10 g, the boll weight increased by 0.01–0.40 g. Therefore, improving the photoassimilate translocation rate in burs is a crucial approach to enhancing the single boll weight under harvest aid application.

Effect of herbicide stress on synchronization of carbon and nitrogen metabolism in lentil (Lens culinaris Medik.)

Weed invasion causes significant yield losses in lentil. Imazethapyr (IM), a broad-spectrum herbicide inhibits the biosynthesis of branched chain amino acids necessary for plant growth. Plant growth depends upon translocation of photo-assimilates and their partitioning regulated by carbon and nitrogen metabolism. This study aimed to investigate the impact of imazethapyr spray on carbon and nitrogen metabolism in tolerant (LL1397 and LL1612) and susceptible (FLIP2004-7L and PL07) lentil genotypes during vegetative and reproductive development. Significantly higher activities of invertases and sucrose synthase (cleavage) in leaves and in podwall and seeds during early phase of development in tolerant genotypes were observed as compared to susceptible genotypes under herbicide stress that might be responsible for providing hexoses required for their growth. Activities of sucrose synthesizing enzymes, sucrose phosphate synthase and sucrose synthase (synthesis) increased significantly in podwalls and seeds of LL1397 and LL1612 genotypes during later phase of development towards maturity while the activities decreased in FLIP2004-7L and PL07 genotypes under herbicide stress. Activities of nitrate and nitrite reductase, glutamine 2-oxoglutarate aminotransferase, glutamine synthetase and glutamate dehydrogenase were increased in leaves, podwalls and seeds of LL1397 and LL1612 under herbicide stress. A proper synchronization of carbon and nitrogen metabolism in tolerant lentil genotypes during vegetative and reproductive phase might be one of the mechanisms for their recovery from herbicide stress. This first ever comprehensive information will provide a basis for future studies on the molecular mechanism of source sink relationship in lentil under herbicide stress and will be utilized in breeding programmes.

Phloem Unloading in Developing Rice Caryopses and its Contribution to Non-Structural Carbohydrate Translocation from Stems and Grain Yield Formation.

Phloem unloading plays an important role in photoassimilate partitioning and grain yield improvements in cereal crops. The phloem unloading strategy and its effects on photoassimilate translocation and yield formation remain unclear in rice. In this study, plasmodesmata were observed at the interface between the sieve elements (SEs) and companion cells (CCs), and between the SE-CC complex and surrounding parenchyma cells (PCs) in phloem of the dorsal vascular bundle in developing caryopses. Carboxyfluorescein (CF) signal was detected in the phloem of caryopses, which showed that CF was unloaded into caryopses. These results indicated that the SE-CC complex was symplasmically connected with adjacent PCs by plasmodesmata. Gene expression for sucrose transporter (SUT) and cell wall invertase (CWI), and OsSUT1 and OsCIN1 proteins were detected in developing caryopses, indicating that rice plants might actively unload sucrose into caryopses by the apoplasmic pathway. Among three rice recombinant inbred lines, R201 exhibited lower plasmodesmal densities at the boundaries between cell types (SE-CC, SE-PC and CC-PC) in developing caryopses than R91 and R156. R201 also had lower expression of SUT and CWI genes and lower protein levels of OsSUT1 and OsCIN1, as well as CWI activity, than R91 and R156. These data agreed with stem non-structural carbohydrate (NSC) translocation and grain yields for the three lines. The nitrogen application rate had no significant effect on plasmodesmal densities at the interfaces between different cells types, and did not affect CF unloading in the phloem of developing caryopses. Low nitrogen treatment enhanced expression levels of OsSUT and OsCIN genes in the three lines. These results suggested that nitrogen application had no substantial effect on symplasmic unloading but affected apoplasmic unloading. Therefore, we concluded that poor symplasmic and apoplasmic unloading in developing caryopses might result in low stem NSC translocation and poor grain yield formation of R201.

Influence of nutrients and plant growth regulators on growth parameters and yield of Pigeonpea (Cajanus cajan (L.) Millsp.)

Pigeonpea is the second most important pulse crop after chickpea in India. The yield of pigeonpea is very low due to indeterminate growth habit and poor source-sink relationship. Plant growth regulators are known to influence the source-sink relationship and stimulate the translocation of photo-assimilates thereby helping in effective flower formation, fruit and seed development and ultimately enhance productivity of the crops. With this background, a field experiment was conducted with pigeonpea (CO Rg 7) under irrigated condition in Tamil Nadu Agricultural University, Coimbatore. An experiment was aimed at determining the effect of various nutrients and growth-promoting hormones on the growth parameters and yield of pigeonpea (Cajanus cajan (L.) Millsp.). The Factorial Randomised Block Design was used in the field trial and was replicated three times. At the vegetative stage, the treatments included foliar sprays of growth inhibitors such as M2-Mepiquat chloride (MC) @ 500 pp, M3-Chlormequat chloride (CC) @ 500 ppm and M1- Control. At flower initiation and 15 days later, various plant growth regulators, such as T2-SA (100 ppm), T3-BR (0.1 ppm), T4-Napthyl acetic acid (40 ppm), T5-Nutrients (ZnSO4 @ 0.5 percent + H3BO3 @ 0.3 percent, T6-Mono Ammonium Phosphate @ 2 percent, and T7-TNAU Pulse Wonder @ 1 percent), T8-Nutrient consortia I (1%) and T9-Nutrient consortia II (1%), were used. Among the treatments, the combination of Chlormequat chloride and nutrient consortia treatments (M3T8&M3T9) had better performances in growth parameters and yield of pigeonpea (CO Rg 7). Foliar application of M3T8-Chlormequat chloride and Nutrient consortia I (1%) resulted significantly (P<0.05) in the highest Total dry matter production (64.85; 82.96 g plant-1), Leaf area (1629; 1873 cm-2 plant-1), Leaf area index (1.358; 1.561), Specific leaf weight (7.29; 10.34 mg cm-2) and Seed yield (1133 kg ha-1) when compared to other treatments. The present study that the application of a combined formulation of hormones and nutrients present in the nutrient consortia at the flowering and pod formation stages influenced the growth parameters and resulted in higher seed yield.

Role of heterosis for photosynthetic traits and sink organs in seed yield enhancement in safflower

Abstract Genetic basis of heterosis has been exploited for yield improvement in safflower (Carthamus tinctorius L.) but little is known about physiological basis of heterosis for yield. The objective of this study was to quantify the physiological basis of heterosis for seed yield in safflower by examining 19 safflower hybrids and their parents for photosynthetic traits, and yield and its components. The results showed that heterosis for yield and its components was high and positive but was low and negative for photosynthetic traits in most of the hybrids studied. There were weak and non-significant relations between photosynthetic traits and yield and its components. Hybrids were more efficient in translocating photoassimilates to two major sink organs viz., number of seeds and number of capitula despite having low net photosynthesis than parents. Seed yield increase in safflower is more sink-than source-limited and was necessary through heterosis for sink organs. Heterosis breeding for larger sink size with parallel increase in effectiveness of sink organs in translocation of photo-assimilates is suggested for yield improvement in safflower.

Phloem connectivity and transport are not involved in mature plant resistance (MPR) to Potato Virus Y in different potato cultivars, and MPR does not protect tubers from recombinant strains of the virus

The aims of this study were: i) to investigate mature plant resistance (MPR) against four strains of Potato virus Y (PVYO, PVYN, PVYNTN and PVYN−Wi) in potato cultivars that differ in maturity (e.g. early or maincrop) at different developmental stages, and ii) to determine whether phloem translocation of photoassimilates at different stages including the source-sink transition influences MPR. The data showed that MPR was functional by the flowering stage in all cultivars, and that the host-pathogen interaction is highly complex, with all three variables (potato cultivar, virus strain and developmental stage of infection) having a significant effect on the outcome. However, virus strain was the most important factor, and MPR was less effective in protecting tubers from recombinant virus strains (PVYNTN and PVYN−Wi). Development of MPR was unrelated to foliar phloem connectivity, which was observed at all developmental stages, but a switch from symplastic to apoplastic phloem unloading early in tuber development may be involved in the prevention of tuber infections with PVYO. Recombinant virus strains were more infectious than parental strains and PVYNTN has a more effective silencing suppressor than PVYO, another factor that may contribute to the efficiency of MPR. The resistance conferred by MPR against PVYO or PVYN may be associated with or enhanced by the presence of the corresponding strain-specific HR resistance gene in the cultivar.

Low Nitrogen Enhances Apoplastic Phloem Loading and Improves the Translocation of Photoassimilates in Rice Leaves and Stems.

The grain filling of rice depends on photoassimilates from leaves and stems. Phloem loading is the first crucial step for the transportation of sucrose to grains. However, phloem loading mechanisms in rice leaves and stems and their response to nitrogen (N) remain unclear. Here, using a combination of electron microscopy, transportation of a phloem tracer and 13C labeling, phloem loading was studied in rice leaves and stems. The results showed that the sieve element-companion cell complex lacked a symplastic connection with surrounding parenchyma cells in leaves and stems. The genes expression and protein levels of sucrose transporter (SUTs) and sugars will eventually be exported transporters (SWEETs) were detected in the vascular bundle of leaves and stems. A decrease in the 13C isotope remobilization from leaves to stems and panicles following treatment with p-chloromercuribenzenesulfonic acid indicated that rice leaves and stems actively transport sucrose into the phloem. Under low-N (LN) treatment, the activities of α-amylase, β-amylase and sucrose phosphate synthase (SPS) in stems and activity of SPS in leaves increased; genes expression and protein levels of SUTs and SWEETs in leaves and stems increased; the 13C isotope reallocation in panicles increased. These indicated that LN enhanced apoplastic phloem loading in stems and leaves. This improved the translocation of photoassimilates and consequently increased grain filling percentage, grain weight and harvest index. This study provides evidence that rice leaves and stems utilize an apoplastic loading strategy and respond to N stimuli by regulating the genes expression and protein levels of SUTs and SWEETs.

Comparative Yield and Photosynthetic Characteristics of Two Corn (Zea mays L.) Hybrids Differing in Maturity under Different Irrigation Treatments

Effective irrigation strategies are of great significance for improving crop yields. There is an increasing concern that short-season corn hybrids are gradually being encouraged to plant in the North China Plain (NCP) with the development of mechanized grain harvesting, but the photosynthetic characteristics and productivity of short-season hybrids are not well documented. The objective of the study was to investigate the effects of different irrigation treatments on photosynthetic characteristics, dry matter accumulation (DMA) and photo-assimilate translocation (PAT/PT), grain yield (GY) and water productivity (WP) of two corn hybrids differing in maturity. In the experiment plots under the rainout shelter facility, short-season hybrid Denghai518 (DH518) and medium- and full-season hybrid Denghai605 (DH605) were grown under three irrigation levels (severe water stress, T1; mild water stress, T2; and non-stress, T3) by two irrigation methods (flood irrigation, FI; surface drip irrigation, SDI) in 2020 and 2021. The results indicated that non-stomatal limitation (NSL) was the main factor leading to the reduction in photosynthesis during the reproductive stage. Severe water stress significantly decreased net photosynthetic rate (Pn) and chlorophyll soil-plant analysis development (SPAD) value, resulting in lower DMA and GY. The contribution rate of vegetative organ photosynthate before flowering (CRP) decreased with the irrigation levels increasing. DMA, GY and WP of SDI increased by 16.23%, 21.49% and 51.31%, respectively, compared to FI. The yields of DH518 were 7.22% lower than those of DH605. The WP penalty for DH605 was attributed to a relatively larger ET. It suggested that applying the optimum irrigation level (T3) under SDI could increase DMA, GY and WP of summer corn in the NCP.

Effects of CO2 Enrichment on Yield, Photosynthetic Rate, Translocation and Distribution of Photoassimilates in Strawberry ‘Sagahonoka’

The method of automatically controlling the CO2 concentration in a greenhouse depending on ventilation was examined in order to efficiently improve the productivity of strawberries under the weather conditions in the northern part of Kyushu in Japan. The effects of CO2 enrichment on the yields, fruit Brix, and economic value of the strawberry ‘Sagahonoka’ were investigated. In addition, in order to clarify the physiological response of ‘Sagahonoka’ to the CO2 concentration, the photosynthetic rate, translocation, and photoassimilate distribution rate were measured. It was found that maintaining the CO2 concentrations above 800 μmol mol−1 and 400 μmol mol−1 during no ventilation and ventilation, respectively, resulted in 25% increases in marketable fruit yields and a 0.2–1.2% higher fruit Brix compared to control, which was kept in 400 μmol mol−1 CO2 or above all day regardless of ventilation. Additionally, the economic value of ‘Sagahonoka’ was increased. The photosynthetic rate of ‘Sagahonoka’ increased linearly up to 800 μmol mol−1 CO2, and high CO2 concentrations affected the distribution for the primary fruit, the most significant sink. It was clarified that CO2 enrichment at 800 μmol mol−1 for ‘Sagahonoka’ was effective in increasing the photosynthetic rate and distribution of photoassimilates to fruits, and the yields of strawberries could be increased efficiently by automatically controlling the CO2 concentration depending on ventilation in a southern region of Japan.

Root:shoot balance controls flush phenology and carbohydrate translocation dynamics in citrus (Citrus x sinensis) trunk.

Flush shoot growth presents a fluctuation pattern alternating with root growth. The cyclic pattern determines the balance of root:shoot and can affect the direction and speed of carbohydrate translocation during the vegetative growth period. In this study, we used water deficit to limit corresponding growth in sweet orange (Citrus x sinensis) "OLL 4" grafted on "US-942" rootstock, and then observed the changes of translocation dynamics between two flush statuses. Our first hypothesis was that water deficit would reduce root growth and extend the root growth phase during the growth cycle, delaying the following flush. We then tested the related second hypothesis that shoot flushes would switch the direction and slow the speed of carbohydrate transport due to fluctuation between single and dual sinks. After recovery from a severe deficit, the flush was synchronized and emerged within 2 weeks. Mild and moderate water-deficit plants showed a delayed new flush. Next, we used a 14 C-labeling method to test whether translocation was affected by the presence of new flush. Basipetal translocation was dominant, but the new flush increased the likelihood of acropetal translocation. Translocation speeds were not different in both directions regardless of flushing status, though speed estimates were highly variable, even though 14 C export from the source leaf increased when new flush was present. The results suggest that flush timing across an environmental gradient is governed by source-sink dynamics. The presence of new flush altered the direction of photoassimilate translocation and rate of leaf export, but stem transport speeds were not distinguishably different.

The Physiological and Biochemical Effects on Napier Grass Plants Following Napier Grass Stunt Phytoplasma Infection

Napier grass stunt (NGS) phytoplasma, a phloem-limited bacterium, infects Napier grass leading to severe yield losses in East Africa. The infected plants are strongly inhibited in growth and biomass production. In this study, phytoplasma-induced morphological changes of the vascular system and physiological changes were analyzed and compared with uninfected plants. The study showed that the phytoplasmas are more abundant in source leaves and range from 103 bacteria/μg total DNA in infected roots to 106 in mature Napier grass leaves. Using microscopical, biochemical, and physiological tools, we demonstrated that the ultrastructure of the phloem and sieve elements is severely altered in the infected plants, which results in the reduction of both the mass flow and the translocation of photoassimilates in the infected leaves. The reduced transport rate inhibits the photochemistry of photosystem II in the infected plants, which is accompanied by loss of chloroplastic pigments in response to the phytoplasma infection stress eventually resulting in yellowing of diseased plants. The phytoplasma infection stress also causes imbalances in the levels of defense-related antioxidants, glutathione, ascorbic acid, reactive oxygen species (ROS), and-in particular-hydrogen peroxide. This study shows that the infection of NGS phytoplasma in the phloem of Napier grass has an impact on the primary metabolism and activates a ROS-dependent defense response.

Can calcium and boron leaf application increase soybean yield and seed quality?

ABSTRACT Nutrient leaf application is complementary to soybean nutritional management, mainly at maturity, when plants present high nutritional demand and high nutrients and photoassimilate translocation rates for seed production. The aim of this research was to evaluate the agronomic performance, physiological quality, and nutritional contents of soybean seeds after application of different rates (0, 0.50, 1.0, 1.5, 2.0, and 2.5 kg ha−1) of foliar fertiliser containing calcium (20%) and boron (4%) at the R3 stage (onset of pod formation). This research was carried out in two sites (Guaragi and Floresta) both in Parana State, Brazil, in randomised complete blocks with 4 replicates. Calcium and boron leaf application increased grain sulphur and nitrogen levels (Guaragi) but reduced phosphorus and magnesium (Floresta). Regarding physiological quality, foliar fertilisation increased the index of germination speed. The yield and number of pods increased up to the rate of 0.6 and 1.2 kg ha−1 of leaf fertiliser in Floresta. Foliar fertilisation with calcium and boron showed advantages, however, results depended on the site, indicating different levels of soil fertility and climatic characteristics.

ABA and BAP improve the accumulation of carbohydrates and alter carbon allocation in potato plants at elevated CO2.

Elevated CO2 interactions with other factors affects the plant performance. Regarding the differences between cultivars in response to CO2 concentrations, identifying the cultivars that better respond to such conditions would maximize their potential benefits. Increasing the ability of plants to benefit more from elevated CO2 levels alleviates the adverse effects of photoassimilate accumulation on photosynthesis and increases the productivity of plants. Despite its agronomic importance, there is no information about the interactive effects of elevated CO2 concentration and plant growth regulators (PGRs) on potato (Solanum tuberosum L.) plants. Hence, the physiological response and source-sink relationship of potato plants (cvs. Agria and Fontane) to combined application of CO2 levels (400 vs. 800µmolmol-1) and plant growth regulators (PGR) [6-benzylaminopurine (BAP) + Abscisic acid (ABA)] were evaluated under a controlled environment. The results revealed a variation between the potato cultivars in response to a combination of PGRs and CO2 levels. Cultivars were different in leaf chlorophyll content; Agria had higher chlorophyll a, b, and total chlorophyll content by 23, 43, and 23%, respectively, compared with Fontane. The net photosynthetic rate was doubled at the elevated compared with the ambient CO2. In Agria, the ratio of leaf intercellular to ambient air CO2 concentrations [Ci:Ca] was declined in elevated-CO2-grown plants, which indicated the stomata would become more conservative at higher CO2 levels. On the other hand, the increased Ci:Ca in Fontane showed a stomatal acclimation to higher CO2 concentration. The higher leaf dark respiration of the elevated CO2-grown and BAP + ABA-treated plants was associated with a higher leaf soluble carbohydrates and starch content. Elevated CO2 and BAP + ABA shifted the dry matter partitioning to the belowground more than the above-media organs. The lower leaf soluble carbohydrate content and greater tuber yield in Fontane might indicate a more efficient photoassimilate translocation than Agria. The results highlighted positive synergic effects of the combined BAP + ABA and elevated CO2 on tuber yield and productivity of the potato plants.

Adubação nitrogenada associada à inoculação de Bradyrhizobium japonicum como estratégia para amenizar os efeitos da desfolha na soja

O nitrogênio (N) promove a fotossíntese, a produção e a translocação de fotoassimilados, bem como aumenta a taxa de crescimento das plantas. Este estudo teve como objetivo avaliar a resposta da soja a desfolha e a doses de N, associada à inoculação de B. japonicum. O delineamento experimental utilizado foi o de blocos casualizados, disposto em esquema fatorial 4 × 4, com quatro repetições. Os tratamentos foram constituídos por quatro níveis de desfolha (0, 33, 66 e 99%) realizado no estádio R3 (legume - canivete com 5mm) e quatro doses de nitrogênio (0, 50, 100 e 150 kg ha–1 de N). A fonte de N utilizada foi a ureia (45% de N), sendo realizadas distribuições manuais a lanço dois dias após a desfolha. Quando os grãos estavam perceptíveis ao tato - 10% de granação (estádio R5.1) foram avaliadas a altura das plantas, teor de clorofila, área foliar e matéria seca aérea. Na colheita foram determinados a inserção do primeiro legume, número de legume, número de grãos por legume, massa de mil grãos, produtividade e o teor de proteínas dos grãos. A adubação nitrogenada não teve a capacidade de amenizar o efeito da desfolha na cultura da soja, independentemente do nível de desfolha e das doses de N na aplicação. Níveis de desfolhas a partir de 30% durante a formação do legume (canivete com 5mm) culminaram na redução da área foliar, matéria seca da parte aérea, altura de plantas, número de legumes por planta, número de grãos por legume, massa de mil grão, produtividade dos grãos e o teor de proteína dos grãos.

Tolerance mechanisms for breeding wheat against heat stress: A review

Heat stress is one of the major abiotic stresses affecting the growth and yield-related characters of wheat. Using various genetic approaches we can develop heat tolerant wheat varieties in order to mitigate the effect of heat stress on wheat production. Currently different strategies have been adopted to develop thermotolerance in wheat. Development of thermotolerant wheat varieties is one of the major steps toward the improvement of wheat yield against heat stress. For this purpose, it is important to have a complete and clear concept of the morpho-physiological, biochemical and molecular mechanisms of heat tolerance in wheat. This review may provide better knowledge about heat tolerance through discussing the morphological, physiological, biochemical and molecular mechanisms of heat tolerance in wheat based on different parameters such as grain filling duration, grain yield, leaf senescence, canopy temperature depression, photosynthesis, chlorophyll content, membrane thermostability, translocation of photo-assimilates, starch synthesis, antioxidant response, protein synthesis and omics approaches.

Low Nitrogen Enhances Apoplastic Phloem Loading and Improves the Translocation of Photoassimilates in Rice Leaves and Stems

Low Nitrogen Enhances Apoplastic Phloem Loading and Improves the Translocation of Photoassimilates in Rice Leaves and Stems