جستجوی مقالات مرتبط با کلیدواژه « photosynthetic rate » در نشریات گروه « زراعت »

When the plant is exposed to abiotic stresses, the cell membrane is the first part of the cell to be affected by stress, and the relationships of the many of physiological and biochemical cell of the plant are disrupted. The effect of three growth hormones (3 indoleacetic acid [IAA], gibberellic acid [GA3] and 6 benzylaminopurine [6 BAP]) with a control (distilled water) was evaluated at booting stage of two wheat cultivars (Rijaw and Azar 2). A factorial experiment using a randomized complete block design (RCBD) with three replications was setup at Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran in 2013-14 and 2014-15. Based on the results, the effect of different growth hormones on SPAD, relative water content, Fv/Fm, performance index, leaf cell membrane stability and photosynthetic rate of both cultivars were significant. Among growth hormones, foliar application of Cytokinin and Auxin had the greatest effect on the measured leaf traits and the lowest mean of the traits was obtained in non-spraying treatment (control). Between the two cultivars, Rijaw cultivar was superior to Azar-2. There was also a positive and significant correlation between cell membrane stability and photosynthesis rate, Fv/Fm and performance index. In general, in dryland conditions (water deficiency) with external application of cytokinin in booting stage in superior wheat cultivar (Rijaw) cell membrane stability, relative water content, photosynthetic rate and Fv/Fm were 16, 18, 38 and 45 percent higher than the control, respectively.

Sunflower, one of the primary oilseed crops worldwide, is cultivated extensively due to its suitability for agricultural needs, high oil yield, and nutritional and medicinal value. However, drought remains the most critical limiting factor affecting sunflower productivity. In arid and semi-arid regions, the intensity of drought stress is predicted to increase in the future. Unfortunately, severe drought stress leads to significant reductions in both seed and oil production. While sunflower is moderately drought-tolerant, understanding the physiological and agronomic aspects of drought stress is crucial for sustainable management. Given that water, scarcity poses a significant threat to crop productivity and environmental resources are diminishing, effective irrigation management under water scarcity is becoming increasingly important.

In order to study the effects of deficit irrigation on grain yield and physiological traits of six sunflower cultivars, a field experiment was carried out in a split-plot arrangement based on randomized complete block design with three replications in 2019-2020 growing season. The experimental site was located in the research farm of the Safiabad Agricultural and Natural Resources Research and Education Center. Main plots consisted of three irrigation regimes including; control, moderate, and severe deficit irrigation (50, 70, and 90% of available moisture, respectively), and sub plots consisted of six sunflower cultivars including; Oscar, Felix, Shakira, Savana, Labad and Monaliza.

Different levels of deficit irrigation differently caused a significant reduction in stomatal conductance, photosynthetic rate, chlorophyll index, relative water content, grain yield, grain number per head, grain weight per head, and oil yield, when compared to control. Oscar cultivar with the highest stomatal conductance, photosynthetic rate, and chlorophyll index, produced the highest economic oil and grain yield while the Shakira cultivar showed the lowest grain yield values in different levels of deficit irrigation. Oscar in 50% of field capacity and Shakira in 90% of field capacity showed the highest and lowest grain yield values (5.34 and 2.67 ton ha-1, respectively). Labad maintained the highest grain yield in 70 and 90% of field capacity relative to the control (4.41 and 4.28 ton ha-1, respectively). It seems that deficit irrigation leads to a significant reduction in grain yield by reducing the reproductive stage, producing fewer seeds, and the impossibility of transferring assimilates to fill the grains. Moreover, the reduction of oil percentage is probably due to the acceleration of achene ripening, giving the plant a chance to escape from drought, because carbohydrates first accumulate in the achenes and then turn into oil or any other substance. Photosynthetic rate, stomatal conductance, light absorption, relative water content, leaf area index, chlorophyll index, and transpiration rate decreased by 49, 25, 28, 26, 48, 22 and 78%, respectively in severe deficit irrigation, while water use efficiency and canopy temperature increased by 58 and 16 % respectively. 

Various levels of deficit irrigation exerted an influence on the physiological characteristics and grain yield of sunflower cultivars. The extent of water scarcity emerged as a significant factor shaping the cultivar responses to deficit irrigation. Felix and Labad exhibited higher oil yield and are thus recommended for cultivation in Dezful and analogous regions, owing to their superior grain yield and ability to sustain grain yield under deficit irrigation conditions.

Deficit irrigation is a water management strategy that reduces water use to the drought sensitive growth stages. In order to study of different deficit irrigation regimes on photosynthetic, morpho-physiological and yield traits of two safflower cultivars, a field experiment was carried out in a split plot arrangement in randomized complete block design with three replications in the research farm of Shahid Chamran University of Ahvaz in 2017-2018. Main plots consisted of four irrigation regimes including; Control (irrigation treatments: 80%, 80%, 80%, and 80% of field capacity), mild deficit irrigation (irrigation treatments: 60%, 80%, 80%, and 40% of field capacity),  moderate deficit irrigation (irrigation treatments: 60%, 60%, 60%, and 60% of field capacity) and severe deficit irrigation (irrigation treatments: 40%, 60%, 60%, and 60% of field capacity), and sub plots consisted of two safflower cultivars including; Padideh and Goldasht. Deficit irrigation treatments were applied at stem elongation, branching, flowering, and grain-filling stages. There was a significant difference between cultivars in terms of most traits and irrigation regimes differently caused a significant reduction in stomatal conductance, photosynthetic rate, number of head per plant, number of grain per head, number of grain per plant, 1000 grain weight, head diameter, height of first secondary branch, plant height, number of secondary branch per plant, biomass yield, harvest index, and grain and oil yield. The grain yield of the both cultivars significantly reduced under mild, moderate and severe water-deficit stresses by 26, 39 and 63%, respectively, relative to the control. The reductions were 31, 43 and 63%, respectively, compared to the control in oil yield. Goldasht showed higher oil yied due to it’s higher grain yield compared to Padideh. Totally, moderate deficit regime as a suitable strategy  of water management to reduce water use and Goldasht cultivar cultivation is defined in this area.

In order to better management of plant performance under conditions of drought stress and study of the condition of plant growth, transpiration, plant stomatal conductance, plant photosynthesis (main determinant of plant growth), photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoid), a completely randomized block design with three replications was conducted in the Faculty of Agriculture of Lorestan University in 2017. The water stress treatments including 100, 80, 60 and 40 Percent of water requirement were applied. Irrigation was performed based on weighing method. Gas exchange measurements and morphological harvesting were done 80 and 90 days after stress. Results showed that water stress treatment has a significant reduction of stomatal conductance, transpiration rate, photosynthesis rate, intercellular CO2 concentration, photosynthetic water use efficiency and carboxylation efficiency. The highest values of the above parameters were related to control treatment and the lowest values were observed in treatment of 40% of water requirement. these values were decreased 68.08%, 59.99%, 61.42%, 37.96%, 20.79% and 37.5%, respectively, compared to the control treatment. As the result showed, the amount of stomatal conductance, transpiration rate, photosynthesis rate are affected by drought stress more than other parameters. Photosynthetic pigments were decreased significantly by increasing drought stress. The highest and lowest of chlorophyll a and b and carotenoid observed in control and heavy drought stress. Finally, drought stress significantly reduced the growth parameters such as plant height, stem diameter, dry weight of the plant.

Water in arid and semiarid regions is a limitation factor and recognition of water use efficiency is an essential parameter in yield increment of the crop plants. An experiment with 100 wheat lines and varieties was conducted in square lattice design (10×10) to identify the effects of different physiological traits on water use efficiency of wheat under rainfed conditions. Leaf relative water content, rate of water lost, photosynthesis rate, intercellular CO2 concentration, transpiration rate, stomatal conductance and chlorophyll index were measured at flowering stage. In stepwise regression analysis of PWUE as dependent variable, photosynthesis rate, transpiration rate and intercellular CO2 concentration entered to model and explained 88% of the total variance of PWUE. Path analysis showed that photosynthesis rate had positive and transpiration rate and intercellular CO2 concentration had negative effects on this trait. According to our results, selection of plants with higher photosynthesis rate and transpiration rate and lower intercellular CO2 concentration is recommended to improve PWUE.

In order to study the interrelations of photosynthetic rate and surfaces and leaf proline content with yield and yield components of safflower under different irrigation regimes, a field experiment in a split plot arrangement under a ranomized complete block design with four replication was performed at Lavark Reasrch Farm, Isfahan University of Technology, Isfahan, Iran in 2007. Two Irrigation levels, including irrigating after 80 mm (control) and 140 mm (water deficit) evaporation from a Standard Class A Pan were served as the main plots. Six safflower genotypes including Arak 2811, Kuseh, Nebraska-10, C111, S149 and K12 were considered as the subplots. Gas exchange rate at heading and flowering, leaf area index (LAI) and leaf proline content at %50 flowering, head/plant, seed/head, 1000 seed weight, grain and biological yield, oil content and oil yield were measured. Net photosynthetic rate differed among irrigation levels and genotypes. At both heading and flowering stages water deficit decreased mean net photosynthetic rate by more than 50% and the smallest mean was observed in genotype S149. Moisture deficit increased leaf proline content by %83, averaged over genotypes and the greatest mean was observed in genotype Kouseh. A 27% decrease in LAI and decreases in seed/head, head/plant and seed weight under water deficit irrigation led to over 27% decreases in grain yield, compared to the control irrigation level. Oil yield and biological yield per plant were decreased by irrigation level. The smallest means for LAI, grain yield, biological yield and oil content were observed in Nebraska-10, C111, Kouseh and S149, respectively. It could be concluded that with genotypes used in this experiment and the environmental conditions in 2007 in Isfahan, water deficit negatively affected both photosynthetic rate and LAI in safflower, resulting in significant decreases in grain and biological yield. An increased level of leaf proline content under water deficit did not prove to enhance the resistance of this oil seed crop to the later environmental constrain.