Carboxylation Efficiency Research Articles

Four distinct leaf types in the Brazilian Cerrado, based on bundle sheath extension morphology

Plant species have been classified as being either heterobaric or homobaric based on the presence or absence (respectively) of bundle sheath extensions (BSE) in leaf veins. These leaf types differ in their physiological performance, and their occurrences tend to be associated with environment. This study investigated the presence/absence of BSE and their structural peculiarities in 49 woody species (28 angiosperm families) in the Brazilian Cerrado using anatomical methods. We measured the gas exchange indices and stomatal density. In addition to typical homobaric (61.2%) and heterobaric (22.4%) species, we also found species with intermediate BSE features. These we call “larger heterobaric” (12.2%) and “semi-heterobaric” (4.1%) species. In the former, BSE occurs around only the secondary veins, whereas in the latter the BSE projects only towards the adaxial leaf surface. The net CO2 assimilation rates, the stomatal conductance, the transpiration rates, and the carboxylation efficiencies were statistically higher in heterobaric than in homobaric species. In the larger heterobaric species, the photosynthetic indices were similar to those in the heterobaric species. Meanwhile, semi-heterobaric species showed photosynthetic indices similar to the homobaric species. We demonstrated that structural variation in the BSE is linked to physiological leaf performance, suggesting some correlation between leaf morphology and plant adaptations.

The photosynthetic and structural differences between leaves and siliques of Brassica napus exposed to potassium deficiency

BackgroundMost studies of photosynthesis in chlorenchymas under potassium (K) deficiency focus exclusively on leaves; however, little information is available on the physiological role of K on reproductive structures, which play a critical role in plant carbon gain. Brassica napus L., a natural organ-succession species, was used to compare the morphological, anatomical and photo-physiological differences between leaves and siliques exposed to K-deficiency.ResultsCompared to leaves, siliques displayed considerably lower CO2 assimilation rates (A) under K-deficient (−K) or sufficient conditions (+K), limited by decreased stomatal conductance (gs), apparent quantum yield (α) and carboxylation efficiency (CE), as well as the ratio of the maximum rate of electron transport (Jmax) and the maximum rate of ribulose 1,5-bisphosphate (RuBP) carboxylation (Vcmax). The estimated Jmax, Vcmax and α of siliques were considerably lower than the theoretical value calculated on the basis of a similar ratio between these parameters and chlorophyll concentration (i.e. Jmax/Chl, Vcmax/Chl and α/Chl) to leaves, of which the gaps between estimated- and theoretical-Jmax was the largest. In addition, the average ratio of Jmax to Vcmax was 16.1% lower than that of leaves, indicating that the weakened electron transport was insufficient to meet the requirements for carbon assimilation. Siliques contained larger but fewer stoma, tightly packed cross-section with larger cells and fewer intercellular air spaces, fewer and smaller chloroplasts and thin grana lamellae, which might be linked to the reduction in light capture and CO2 diffusion. K-deficiency significantly decreased leaf and silique A under the combination of down-regulated stomatal size and gs, chloroplast number, α, Vcmax and Jmax, while the CO2 diffusion distance between chloroplast and cell wall (Dchl-cw) was enhanced. Siliques were more sensitive than leaves to K-starvation, exhibiting smaller reductions in tissue K and parameters such as gs, Vcmax, Jmax and Dchl-cw.ConclusionSiliques had substantially smaller A than leaves, which was attributed to less efficient functioning of the photosynthetic apparatus, especially the integrated limitations of biochemical processes (Jmax and Vcmax) and α; however, siliques were slightly less sensitive to K deficiency.

Gas exchange and antioxidant activity in seedlings of C opaifera langsdorffii Desf. under different water conditions.

The aim of this study was to evaluate gas exchange, efficiency of the photosynthetic apparatus, and antioxidant activity in Copaifera langsdorffii Desf. The seedlings were cultivated under different conditions of water availability, in order to improve the utilization efficiency of available water resources. The seedlings were cultivated in four different water retention capacities (WRC- 25%, 50%, 75%, and 100%), and evaluated at four different time (T- 30, 60, 90, and 120 days). During the experimental period, seedlings presented the highest values for carboxylation efficiency of Rubisco (A/Ci), intrinsic water use efficiency (IWUE = A/gs), chlorophyll index, and stomatal opening, when grown in the substrate with 75% WRC, but the stomatal index (SI) was less the 25% WRC. The efficiency of photosystem II was not significantly altered by the treatments. Comparison between the extreme treatments in terms of water availability, represented by 25% and 100% WRC, represent stress conditions for the species. Water availability causes a high activity of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) in the plant.

Photosynthetic and enzymatic metabolism of Schinus terebinthifolius Raddi seedlings under water deficit

ABSTRACT Schinus terebinthifolius Raddi is a tree species that can be used in the recovery of degraded areas, as it exhibits rapid growth and has a very expansive root system, facilitating water uptake from the deeper layers of the soil. The objective of this study was to evaluate photosynthesis and enzymatic activity in S. terebinthifolius seedlings under conditions of water deficit and their potential to recover following re-irrigation. The experiment was conducted in a greenhouse under a plastic covering where plants were distributed into two groups: Group 1 - control plants, where irrigation was maintained at 70% of the water retention capacity, and Group 2 - stressed plants, where irrigation was suspended until the photosynthetic rate neared zero, followed by rehydration for 12 days, then a further suspension of irrigation. At the beginning of the experiment and during the suspension of irrigation and rehydration, plants were evaluated for gas and antioxidant enzyme exchanges. Hydric stress significantly reduced photosynthesis, stomatal transpiration conductance, carboxylation efficiency of Rubisco, and the chlorophyll content of the S. terebinthifolius plants. Following rehydration, plants recovered the carboxylation efficiency of Rubisco, but not the photosynthetic rate. Antioxidant enzyme activity increased in both the aerial part and the root in response to water deficit.

Morfofisiologia do crescimento vegetativo inicial de cafeeiros arabica submetidos a aplicação via foliar de Paclobutrazol

Objetivou-se com o presente estudo avaliar respostas morfológicas e fisiológicas durante o crescimento vegetativo inicial de plantas cv. Catuaí Vermelho IAC 144 submetidas à aplicação via foliar de quatro concentrações (250, 500, 750 e 1000 mg L-1) de pacloblutrazol (PBZ) e uma testemunha. O experimento foi conduzido em casa de vegetação com uma planta por vaso, em blocos ao acaso. Avaliaram-se o diâmetro do caule, número de folhas, massas fresca e seca da planta, índice SPAD, área foliar, potencial hídrico foliar e trocas gasosas. Os dados foram submetidos à análise de variância geral e da regressão. As características morfológicas foram afetadas pelo PBZ, ocorrendo redução do crescimento da parte aérea e elevação do peso de massa seca de raízes quando comparada à testemunha. Para os parâmetros fisiológicos o PBZ resultou em impactos positivos como a elevação do índice SPAD, do potencial hídrico foliar antemanhã, da fotossíntese líquida e da eficiência de carboxilação. A taxa de fotossíntese líquida potencial foi afetada pela eficiência da carboxilação, e a transpiração foi associada à maior disponibilidade hídrica da planta. O PBZ alterou a relação entre parte aérea e raiz, favorecendo o crescimento das raízes e otimizando as relações de trocas gasosas, devido à elevação do status hídrico da planta. Os efeitos do PBZ foram mais evidentes na morfologia do crescimento inicial dos cafeeiros quando comparados às alterações fisiológicas.

Anatomical, morphological, and physiological responses of two sugarcane genotypes of contrasting susceptibility to Mahanarva fimbriolata (Hemiptera: Cercopidae).

The purpose of this study was to investigate and compare root morpho-anatomical traits and physiological responses of susceptible (SP81-3250) and resistant (H. Kawandang) sugarcane genotypes exposed to the attack by nymphs of spittlebug Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae). Two experiments were conducted to compare the damage caused by spittlebug nymphs on fresh and dry biomass weight; lignin content in stalks; root anatomy; chlorophyll content; photosynthetic rate (A); carboxylation efficiency (A/Ci); stomatal conductance (gS) and transpiration rate (E) of these genotypes. SP81-3250 consistently obtained significantly higher damage scores than H. Kawandang in both experiments, confirming the previously observed level of resistance in each genotype. Attack by spittlebug nymphs had a much higher effect on both fresh and dry biomass weight, chlorophyll content, A, A/Ci, gs and E of SP81-3250, than that on H. Kawandang. Anatomical studies indicated the presence of aerenchyma tissue in the root cortex of SP81-3250, a feature which may facilitate penetration of the nymph's stylet into the vascular cylinder. In contrast, roots of H. Kawandang are characterized by having more dense and compact parenchyma cells. In addition, infested plants of this genotype contained an unidentified mucilaginous compound in the vascular cylinder of the roots. We conclude that resistance of H. Kawandang to spittlebug is related to the ability of this genotype to maintain normal chlorophyll content, as well as stomatal conductance and photosynthesis, thus, allowing for biomass accumulation under spittlebug attack, in contrast to SP81-3250. In addition, the presence of more compact and denser parenchymal cells, as well as that of an induced mucilaginous compound in the root's vascular cylinder, are likely to hinder host-feeding activity in nymphs, causing higher nymph mortality and therefore, reduced damage in plants of this genotype.

Gas Exchanges of Yellow Capsicum Fertilized with Yellow Water and Cassava Wastewater

Wastewater reuse has increasingly become a sustainable alternative to the efficient use of water as well as the mitigation of the negative environmental impacts generated by the release of the water to the environment in an indiscriminate way. Thus, it is very important to know and evaluate the physiological variables of gas exchanges of plants cultivated with these waters, in order to obtain precise answers their effects on plant physiology. The present study aimed to evaluate the gas exchange of yellow capsicum cultivated in soil fertilized with human urine and cassava wastewater. The experiment was conducted in a protected environment at the Federal University of Campina Grande, Campina Grande - PB. A completely randomized design with eight treatments and five replications was used. The treatments were cattle manure (T1); NPK (T2); human urine treated (T3); cassava wastewater (T4); (T3)+(T4); 2x(T3); 2x(T4); 2x(T3+T4). The volumes of the biofertilizers were defined according to the nitrogen and potassium contents of urine and cassava wastewater, respectively. At 15 and 30 days after transplanting, the variables of gas exchange, the efficient use of water and the instantaneous efficacy of carboxylation were evaluated. The data were submitted to Tukey test at 5% probability. The results indicated that there wasn’t statistical difference for efficient use of water (UEA) evaluated at 30 DAT.The treatment 5 provided the best results in relation to gas exchange, for the variables internal concentration of CO2 (Ci), net assimilation rates of CO2 (A), stomatal conductance (gs), leaf transpiration (E), higher efficiency of water use (UEA) and instantaneous carboxylation efficiency at 15 DAT, so for 30 DAT the biofertilizer that provided the best results was the T4 treatment, although there weren’t significant statistical differences among the treatments for (UEA), except for of T5.

Physiological changes modulated by rootstocks in atemoya (Annona x atemoya Mabb.): gas exchange, growth and ion concentration

Incompatibility reactions of grafted plants are triggered at the moment of grafting and/or at the early stages of re-establishment vascular connections plants; moreover, incompatibility may occur after years in orchard. The objective of this study was to evaluate the gas exchange, growth and ion concentrations on early stage after grafting to atemoya scion (Annona x atemoya Mabb.), an interspecific hybrid between cherimoya (Annona cherimola Mill.) and sweetsop (Annona squamosa L.), commonly used in food industry and for ‘in natura’ consumption, grafted onto biriba rootstock [Annona mucosa (Bail.) H. Rainer] and Annona emarginata (Schltdl.) H. Rainer var. terra-fria and mirim rootstocks to elucidate the physiological mechanisms between grafted plants. Different types of rootstocks evaluated caused variations on scion gas exchange 60 days after grafting (DAG), and these variations reflected in changes in growth at 90 DAG, which was also influenced by differential ion accumulation for each rootstock. The biriba rootstock demonstrated an increase in net carbon assimilation related to carboxylation efficiency and transpiration; however, this rootstock did not result in increased water-use efficiency. The rootstocks exhibited differences in scion leaf ion accumulation, particularly phosphorus and potassium, in biriba and araticum-de-terra-fria, respectively. We concluded that biriba rootstocks increased gas exchange and ion concentration in the atemoya scion, which were reflected directly in the vegetative growth of the scion, indicating that the physiological changes caused by this rootstock to scion do not trigger early incompatibility.

Acclimation to higher VPD and temperature minimized negative effects on assimilation and grain yield of wheat

Adapting to climate change and minimizing its negative impact on crop production requires detailed understanding of the direct and indirect effects of different climate variables (i.e. temperature, VPD). We investigated the direct (via heat stress) and indirect effects (through increased VPD) of high temperature on growth, physiology and yield of two wheat cultivars (Taifun and Vinjett) at two watering levels; well-watered: WW (100% evapotranspiration (ET)) and drought stress: DS (50% of WW ET). Three climate treatments were applied for five days, starting at one week after anthesis. Treatments included hot humid (HH: 36°C; 1.96kPa VPD), hot dry (HD: 36°C; 3.92kPa VPD) and normal (NC: 24°C; 1.49kPa VPD). Difference between HH and HD was considered as the indirect effect of temperature through increased VPD. HD increased transpiration by 2–22% and decreased photosynthetic water-use efficiency (WUEp) by 24–64% over HH during stress but whole-plant WUE at final harvest was not affected. HD reduced grainfilling duration (3days), resulted in relatively lower green leaf area (GLA) after the stress and showed a tendency of lower net assimilation rate during the stress compared to HH. However, yield and yield components were not affected under WW conditions due to two reasons (i) acclimation of the photosynthesis, stomatal conductance and rubisco carboxylation efficiency to high temperature and VPD and (ii) translocation of assimilates from stem/leaf to grains after the stress episode. Five days of high temperature stress alone (HH) reduced GLA, grainfilling duration (5days) and thousand-grain weight (17%), which ultimately reduced grain yield by 17%. DS mainly affected GLA, grainfilling duration and reduced grain yield by 7% vis-à-vis WW. Two cultivars differed only for GLA (lower for Vinjett under HH) and WUEp (higher for Vinjett under DS). This indicates that the temperature induced increase in VPD has little effect on growth and yield, if sufficient soil moisture is available, because acclimation and tolerance mechanisms tend to alleviate stress effects. These compensatory mechanisms should also be considered when modelling climate effects on crops. However, heat waves and drought events during sensitive crop developmental stages (i.e. anthesis, grainfilling) are important climate variables that need to be considered for adaption to climate change.

Influence of High Temperature on Photosynthesis, Antioxidative Capacity of Chloroplast, and Carbon Assimilation among Heat-tolerant and Heat-susceptible Genotypes of Nonheading Chinese Cabbage

High temperature (HT) is a major environmental stress limiting oversummer production of nonheading Chinese cabbage (NHCC, Brassica campestris ssp. chinensis Makino). In the present study, the effects of HT on photosynthetic capacity, including light reaction and carbon assimilation, were completely investigated in two NHCC, ‘xd’ (heat-tolerant), and ‘sym’ (heat-susceptible). The two genotypes showed significant differences in plant morphology, photosynthetic capacity, and photosynthate metabolism (carboassimilation). HT caused a decrease in photosynthesis, chlorophyll contents, and photochemical activity in NHCC. However, these main photosynthetic-related parameters, including net photosynthetic rate (PN), maximal photochemical efficiency of PSII (Fv/Fm), and total chlorophyll content in ‘xd’, were significantly higher than those of ‘sym’ plants. The antioxidant contents and antioxidative enzyme activities of ascorbic acid-reduced glutathione cycle in the chloroplast of ‘xd’ were significantly higher than those of ‘sym’. Microscopic analyses revealed that HT affected the structure of photosynthetic apparatus and membrane integrity to a different extent, whereas ‘xd’ could maintain a better integrated chloroplast shape and thylakoid. Inhibited light reaction also hampered carbon assimilation, resulting in a decline of carboxylation efficiency and imbalance of carbohydrate metabolism. However, larger declined extents in these data were presented in ‘sym’ (heat-susceptible) than ‘xd’ (heat-tolerant). The heat-tolerant genotype ‘xd’ had a better capacity for self-protection by improved light reaction and carbon assimilation responding to HT stress.

Chlorophyll a fluorescence reveals adaptation strategies in drought stress in Ricinus communis

Ricinus communis L. cultivation is an economic alternative in arid regions, particularly in India, China and northeastern Brazil. Research on photosynthetic behavior under conditions of water deficit is valuable for genetic improvement programs and the management of this crop. We aimed to obtain information on the photosynthetic mechanisms and acclimation to stress in young plants of the castor cultivars BRS Gabriela and IAC Guarani grown in the greenhouse, for which irrigation had been suspended for 35 days. Chlorophyll a fluorescence transient and gas exchange were measured every 7 days, and growth was measured at the end of the experiment. Growth and gas exchange were negatively affected by stress, with reductions being detected early during the period of water deficit. There was an increase in water-use efficiency in both cultivars, as well as a reduction in intrinsic carboxylation efficiency. Although gas exchange was reduced initially, the parameters of the JIP test, calculated from the fluorescence transient, indicated an increased activity of the photochemical apparatus, with higher performance indices. A decrease in the activity of the electron transport chain was observed at the end of the stress period, with a concomitant increase in the dissipation and inactivation of photosystem II reaction centers and a consequent reduction in performance indices, with IAC Guarani plants showing greater susceptibility to stress compared to BRS Gabriela plants. Considering the photosynthetic activity in stressed plants, castor bean plants show acclimation of electron transport during the short-term water deficit, however, with decrease in the photosynthesis in long term.

Trocas gasosas de plantas de Handroanthus impetiginosus (Mart. ex DC) Mattos submetidas ao déficit hídrico e posterior reidratação

Knowledge of aspects related to the ecophysiology of plant species present in Caatinga is scarce, needing studies that allow the understanding of the adaptations made by plants to be able to survive under conditions of low water availability. Accordingly, this study was developed with the purpose of analyzing the gas exchange of ipe-roxo seedlings subjected to progressive water stress, through the suspension of irrigation, and rehydration. 12 month old plants, growing up in black plastic bags containing 5 kg of substrate, were subjected to two treatments: irrigated and water stress imposed by withholding water. The relative water content, stomatal conductance, transpiration rate, intercellular CO2 concentration, and photosynthetic rates were evaluated daily. After ten days remaining under this stress condition, irrigation was restored, and recovery was evaluated. Drought stress decreased rapidly and also progressively the relative water content, stomatal conductance, transpiration, carboxylation efficiency and photosynthesis of plants. An increase in intercellular CO2 concentration with increase of water stress was observed. After the resumption of water supply, the plants showed recovery of these physiological processes. Water stress did not affect the water efficiency use of plants.

Effects of the fungicides azoxystrobin, pyraclostrobin and boscalid on the physiology of Japanese cucumber

Abstract Strobilurins are fungicides with beneficial physiological effects on crop yield due to promotion of net carbon assimilation, nitrate reductase enzyme activity, stress tolerance and hormonal balance. The carboxamides complement the action of the strobilurins when applied alternately or together. This study aimed to evaluate the effect of application of pyraclostrobin, azoxystrobin and boscalid on grafted and ungrafted Japanese cucumber (Cucumis sativus L.) in order to analyze the effects of these fungicides on plant physiology and increased fruit production. The experimental design was completely randomized in a 2 × 5 factorial scheme, with grafted and ungrafted cucumber plants and 5 fungicide treatments: control; azoxystrobin 60 g a.i ha−1; boscalid 50 g a.i ha−1; pyraclostrobin 50 g a.i ha−1; and boscalid 100 g a.i ha−1 + pyraclostrobin 50 g a.i ha−1, applied 18 days after transplanting and then at intervals of seven days. The effect of the treatments was evaluated based on the average yield and fruit mass, in addition to observations of gas exchange, lipid peroxidation, and the activities of peroxidase, superoxide dismutase, catalase and nitrate reductase. Based on the results obtained, it was concluded that the fungicide treatments resulted in different responses between the grafted and ungrafted plants. The physiological benefits were more evident in the grafted plants treated with pyraclostrobin or boscalid alone, and these benefits manifested in terms of fruit production and increased the activity of the antioxidative system, thereby reducing stress. The higher productivity probably occurred due to the better physiological performance of these plants, mainly at the beginning of development, presenting greater activity of the enzyme nitrate reductase, in addition to the higher net CO2 assimilation and carboxylation efficiency.

Effect of Mahanarva fimbriolata (Hemiptera: Cercopidae) Attack on Photosynthetic Parameters of Sugarcane Genotypes of Contrasting Susceptibility

The aim of this study was to compare the effect of spittlebug Mahanarva fimbriolata Stål (Hemiptera: Cercopidae) on photosynthetic parameters of both a susceptible (SP81-3250) and a resistant (H.Kawandang) sugarcane genotype. In the first assay, the susceptibility level of genotypes to spittlebug was confirmed by comparing damage score and chlorophyll content of the plants. In the second assay, the effect of spittlebug nymphs on photosynthetic characteristics was assessed using the following parameters: Net photosynthetic rate (A), carboxylation efficiency (A/Ci), stomata conductance (gS), transpiration (E), electron transport rate (ETR), maximum quantum yield of Photosystem 2 (PSII) (FV/FM), effective quantum yield (Y(II)), photochemical quenching (Y(NPQ)), and nonphotochemical quenching (Y(NO)). Spittlebug nymphs affected the photosynthetic process of the susceptible genotype SP81-3250 by decreasing the Chl content, ETR, FV/FM, and Y(II). However, this genotype was able to maintain A probably due to its ability to maintain stomata aperture, increase the carboxylation efficiency of Rubisco, and dissipate excess energy through the xanthophyll cycle, as Y(NPQ) increased under the spittlebug attack. On the other hand, the spittlebug did not affect Chl content and FV/FM of the H.Kawandang genotype. Furthermore, H.Kawandang increased A to compensate for the sink demand by the spittlebug by increasing stomatal aperture and carboxylation efficiency and increasing efficiency of the photochemical apparatus in converting light energy into chemical products. We can conclude that the feeding habits of spittlebug nymphs have different impacts on photosynthesis of susceptible and resistant sugarcane genotypes.

Ecophysiological responses to excess iron in lowland and upland rice cultivars

Iron (Fe) is an essential nutrient for plants but under high concentrations, such as that found naturally in clay and waterlogged soils, its toxic effect can limit production. This study aimed to investigate the stress tolerance responses exhibited by different rice cultivars. Both lowland and upland cultivars were grown under excess Fe and hypoxic conditions. Lowland cultivars showed higher Fe accumulation in roots compared with upland cultivars suggesting the use of different strategies to tolerate excess Fe. The upland Canastra cultivar displayed a mechanism to limit iron translocation from roots to the shoots, minimizing leaf oxidative stress induced by excess Fe. Conversely, the cultivar Curinga invested in the increase of R1/A, as an alternative drain of electrons. However, the higher iron accumulation in the leaves, was not necessarily related to high toxicity. Nutrient uptake and/or utilization mechanisms in rice plants are in accordance with their needs, which may be defined in relation to crop environments. Alterations in the biochemical parameters of photosynthesis suggest that photosynthesis in rice under excess Fe is primarily limited by biochemical processes rather than by diffusional limitations, particularly in the upland cultivars. The electron transport rate, carboxylation efficiency and electron excess dissipation by photorespiration demonstrate to be good indicators of iron tolerance. Altogether, these chemical and molecular patterns suggests that rice plants grown under excess Fe exhibit gene expression reprogramming in response to the Fe excess per se and in response to changes in photosynthesis and nutrient levels to maintain growth under stress.

CcaA and FBP/SBPase Derived From Cyanobacteria Improved Photosynthetic Capacity in Rice

Two cyanobacterial genes ccaA and FBP/SBPase related to CO2 hydration and Calvin cycle were induced into rice plants. Three homologous transgenic strains were generated with ccaA and FBP/SBPase alone or in combination independently and grown under field conditions. The biochemical, physiological, and leaf anatomic results indicated that stomatal and mesophyll conductance to CO2, net photosynthetic rate, carboxylation efficiency, and other physiological and biochemical parameters increased significantly in the overexpression strains with FBP/SBPase and CcaA + FBP/SBPase but not in the CcaA strain. Leaf anatomy structure showed no significant modifications between the transgenic and wild-type strains. The CcaA protein was shown to be located in the cytoplasm. These results showed that the effect on improving photosynthetic capacity by FBP/SBPase was better than by CcaA, and only when CcaA was co-transformed with FBP/SBPase was the synergistic effect observed. The multigene-stacking approaches and their synergistic action for improving the photosynthetic capacity in rice are discussed.

Effects of day and night temperature on photosynthesis, antioxidant enzyme activities, and endogenous hormones in tomato leaves during the flowering stage

ABSTRACTTo study the effects of day and night temperature difference (DIF) on tomato growth, a controlled experiment using Solanum lycopersicum L., cv. Jinguan 5 was conducted. The daily mean temperature (Tm) was maintained at 18°C and 25°C, and the DIF was set at 0°C, 6°C, and 12°C. The results indicated that chlorophyll a (Chl a) and chlorophyll b (Chl b) gradually increased as DIF rose. At 18°C Tm, the carotenoid content reached a maximum at 12°C DIF. The Chl a/Chl b, net photosynthetic rate (PN), photosynthetic rate at irradiation saturation (Pmax), stomatal conductance (gs), intercellular CO2 concentration (Ci), stomatal limitation value, the maximum assimilation rate (Amax), apparent quantum efficiency (Aq), carboxylation efficiency (Ce), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), gibberellin A3 (GA3), and indole-3-acetic acid (IAA) were highest, while malondialdehyde (MDA) was lowest at 6°C DIF. At 25°C Tm, PN, Pmax, Amax, Aq, Ce, gs, Ci, CAT, POD, GA3, IAA, and zeatin reached the maximum under 6°C DIF, while SOD and MDA reached the maximum under 12°C DIF. Furthermore, the morphological index peaked at 6°C DIF under 18°C and 25°C Tm. The results suggested that 6°C DIF improved the growth and development of tomato during the flowering stage.ABBREVIATIONS: Aq – apparent quantum efficiency; Amax – the maximum assimilation rate; CAT – Catalase; Chl a(b) – chlorophyll a(b); Ca – ambient CO2 concentration; Ce – carboxylation efficiency; Ci – intercellular CO2 concentration; DIF – difference between day temperature (TD) and night temperature(TN); FM – fresh mass; gs – stomatal conductance; GA3 – gibberellin A3; IAA – indole-3-acetic acid; Ls – stomatal limitation value; MDA – malondialdehyde; Pmax – photosynthetic rate at irradiation saturation; PN – net photosynthetic rate; POD – peroxidase; ROS – reactive oxygen species; SOD – superoxidedismutase; Tm – daily mean temperature; ZT – zeatin.

Effects of supplement with sanitary landfill leachate in gas exchange of sunflower (Helianthus annuus L.) seedlings under drought stress.

Sanitary landfill leachate is one of the major problems arising from disposal of urban waste. Sanitary landfill leachate may, however, have use in agriculture. This study, therefore, aimed to analyze initial plant growth and gas exchange in sunflower seedlings supplemented with sanitary landfill leachate and subjected to drought stress through variables of root fresh mass (RFM), shoot fresh mass (SFM), total fresh mass (TFM), relative chlorophyll content (CL), stomatal conductance (g s ), transpiration rate (E), net photosynthetic rate (A), ratio of internal to external CO2 concentration (Ci/Ca),water use efficiency (EUA), instantaneous carboxylation efficiency (A/Ci), and electron transport rate (ETR). The experimental design was a completely randomized 2 (irrigated and non-irrigated)×4 (sand, sand + 100kg Nha-1 organic fertilizer, sand + 100kg Nha-1 sanitary landfill leachate, and sand + 150kg Nha-1 sanitary landfill leachate) factorial with five replicates. Under drought stress conditions, leachate treatment supplemented with 100kg Nha-1 exhibited higher plant fresh weights than those of the treatment containing 150kg Nha-1. Increases in fresh mass in plant treatments supplemented with 100 and 150kgN ha-1 sanitary landfill leachate were related to higher photosynthetic rates.

INFLUENCE OF GLYPHOSATE ON SUSCEPTIBLE AND RESISTANT RYEGRASS POPULATIONS TO HERBICIDE

ABSTRACT In Brazil, ryegrass (Lolium multiflorum) has been identified as resistant to glyphosate, becoming a major problem, especially in crops cultivated in the winter season. This herbicide can indirectly affect photosynthesis by inhibiting biosynthesis of many compounds. Thus, the aim of this study was to investigate the influence of glyphosate on the physiological profile of susceptible and resistant ryegrass populations to the herbicide. The experimental design was completely randomized with two treatments (720 and 1,080 g e.a. ha-1) and four replications plus control with no treatment. Two ryegrass populations were sown, one susceptible and another one resistant to glyphosate. After the treatments, evaluations were carried out at 1, 3, 7 and 28 days after application (DAA). Variables analyzed were: CO2 net assimilation rate, stomatal conductance, CO2 internal concentration, transpiration, water use efficiency and instantaneous carboxylation efficiency. The glyphosate herbicide caused irreversible damage in a susceptible population which at 28 DAA in all variables analyzed this population was already dead and it was impossible to analyze it, but it was shown that the effects of this herbicide were intensified from the third day after application. In the case of the resistant population, at 3 DAA in all variables, it suffered significant effects comparing to the control, showing that even with a high level of resistance the herbicide can affect its metabolism.

Effect of fertigation with potassium and nitrogen on gas exchange and biomass accumulation in eggplant1

ABSTRACT Adequate crop fertilization is one of the challenges for agriculture. Measuring gas exchange and biomass accumulation may be used to adjust crop management. The effect of fertigation with potassium (0 kg ha-1, 54 kg ha-1, 108 kg ha-1 and 216 kg ha-1) and nitrogen (0 kg ha-1, 67 kg ha-1, 134 kg ha-1 and 268 kg ha-1) on gas exchange and biomass accumulation in eggplant was assessed under greenhouse conditions. The net photosynthesis, stomatal conductance, transpiration, internal CO2 concentration, instantaneous carboxylation efficiency, water-use efficiency and total dry weight were evaluated. With the exception of K for water-use efficiency and N for internal CO2 concentration, all the other gas exchange parameters were significantly affected by the K and N doses. There was an interaction between N and K doses for net photosynthesis, stomatal conductance, transpiration and instantaneous carboxylation efficiency. The highest values for net photosynthesis, stomatal conductance, transpiration rate, carboxylation instantaneous efficiency and total dry weight were found in the range of 125-185 kg ha-1 of K and 215-268 kg ha-1 of N.