Fertilization regimes under hot conditions alter photosynthetic response of bean plants

Abstract

Various physiological damages occur in plants upon exposure to heat stress (Hasanuzzaman et al. 2013). High temperatures (heat stress, HS) are known to inhibit enzyme activity, net photosynthetic rate (P N ), and other metabolic processes leading to physiological and biochemical alterations (Salvucci and Crafts-Brander 2004, Hassan, 2006, Zhao et al. 2008, ICPP 2014. HS uncouples enzymes and metabolic pathways leading to accumulation of harmful reactive oxygen species (ROS) which are responsible for oxidative stress (Sarieva et al. 2010). The reaction centers of PSI and PSII in chloroplasts are major sites of ROS generation (Chakraborty et al. 2011). Stomatal closure, reduction in root growth, and consequent inhibition of mineral uptake are common responses to HS (Huang and Xu 2000).Nitrogen as an essential element (Sánchez et al. 2004, Cechin and De Terezinha 2004) promotes metabolic activities, such as photosynthesis, antioxidant activities, leading to enhancing in growth and yield (Zhao et al. 2008).Due to their different physiological effects, HS and N fertilization might have interactive impacts on plants. HS reduces the rate of nutrient uptake; however, this effect could be mitigated by excessive supply of N (Altenbach et al. 2003, Zhao et al. 2008, Demmig-Adams et al. 2014. Moreover, Zhang et al. (2014) reported that N nutrition control is an important way to enhance tolerance to abiotic stress. Thus, it is important to understand how the supply of N may mitigate HS.The aim of the present experiment was to study the effects of N-fertilization on alleviation of the negative impact of HS on Chl fluorescence, P N , and stomatal conductance (g s ) of French bean plants.Seeds of French bean (Phaseolus vulgaris L.) were obtained from the Department of Agronomy, Alexandria University, Egypt. They were sown in plastic pots (20 cm 2 ), five seeds in each pot with multipurpose compost in a heated glasshouse [temperature of 24/20ºC day/night, air humidity 60-65%, 16-h photoperiod with additional irradiance of 450 μmol(photon) m -2 s -1 , total irradiance was 975 μmol(photon) m -2 s -1 ]. After appearance of expanded trifoliate leaf, 12 days after sowing (DAS), plants were thinned to one seedling per pot. Pots were then transferred to eight closed climate controlled growth chambers. Two chambers were used for N fertilization as foliar spray (three concentrations of urea: 5, 10, 15 mM). Two other

Radish (Raphanus sativus L.) Cultivar‐Specific Response to O3: Patterns of Biochemical and Plant Growth Characteristics

“…Net photosynthetic rate ( A ) and stomatal conductance ( g s ) were measured on the first expanded leaf of each plant between 10 am to 3 pm using a portable IRGA (Model ADC LCA2). When the leaf showed severe visible O 3 damage, it was replaced by the next youngest leaf . Measurements were carried out seven times (0, 5, 10, 15, 20, 25, and 30 days of fumigation).…”

“…Measurement of chlorophyll fluorescence parameters (maximum efficiency of photosystem II (PSII) photochemistry, F v / F m ; photochemical efficiency of PSII, ϕ PSII ) was done with a plant efficiency analyzer (PEAMK2‐9414, Hansatech Instruments, UK) on the same leaves (where photosynthesis was measured) between 11 am to 1 pm …”

Impacts, Tolerance, Adaptation, and Mitigation of Heat Stress on Wheat under Changing Climates

“…Efficient nutrient management is one way to reduce the impact of HS and sustain crop productivity. Optimization of nitrogen (N) supply sustained the wheat yield by increasing the stomatal conductance, chlorophyll contents and photosynthetic rate under elevated temperature [ 38 , 229 ]. The application of nitric oxide form of N protects the plant from oxidative damage by functioning as scavenger of ROS.…”

Assessing ambient ozone injury in olive (Olea europaea L.) plants by using the antioxidant ethylenediurea (EDU) in Saudi Arabia

“…Measurements were performed at ambient CO 2 concentrations (340-350 ppm) at 60-65 % RH. The chamber was illuminated by a LED lamp (6400-02B LED, LI-COR, Lincoln NE, USA), and an automatic, accurate, and stable temperature control was standard and integral with leaf cuvette (Hassan et al 2015). Net photosynthetic rate (P n ) was measured at 1200-1400 μmol photons m −2 s −1 .…”