Original Article

, Volume: 22( 3) DOI: 10.37532/0974-7419.2022.22(3).187

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Under Both Steady-State and Flecked Irradiance, Nitrogen Can Reduce the Inhibition of Photosynthesis Caused by High Temperature Stress.

*Correspondence:

Tim JasonManaging Editor, Analytical Chemistry: An Indian Journal, Belgium, E-mail: timjason785@hotmail.com

Abstract

One of the most vital nutrients for plants, nitrogen, is directly linked to photosynthesis. Under steady-state and flecked irradiance, high temperature stress severely reduces photosynthesis. Nitrogen's potential to mitigate the decline in photosynthesis brought on by high temperatures, particularly when exposed to flecked light, is unknown. In the current work, rice plants were used in a pot experiment with two nitrogen (N) sources, and the steady-state and dynamic photosynthetic rates were determined at 28 and 40°C. Under conditions of high N supply (HN), high temperatures considerably enhanced leaf hydraulic conductance (Kleaf), but not under conditions of low N supply (LN). Under HN, the higher Kleaf kept the leaf water potential (leaf) and steady-state stomatal conductance (gs,sat) constant, but under high temperatures, the leaf and gs, sat were significantly reduced. The temperature in LN circumstances. Because of this, steady-state photosynthesis (Asat) under high temperatures in the LN conditions decreased more drastically. High temperatures considerably slowed down photosynthesis after switching from low to high light, which increased carbon loss under flecked irradiance. So, less so than with LN supply, these results were attained with HN supply. The inhibition of photosynthesis brought on by high temperature stress can therefore be alleviated by nitrogen under both steady-state and flecked irradiance

Keywords

 Photosynthesis; Biotechnology; Biological

Introduction

Crop yields are under threat from global warming. According to Lobell and Asner, the output of maize and soybeans might drop by up to 17% for every 1°C increase in the growing season temperature. According to experimental data on rice production, the yield of rice reduces by 10% for every 1°C increase in the growing season's minimum temperature. Crop development and output depend heavily on photosynthesis, which is temperature-sensitive. In rice plants, photosynthesis typically peaks at around 30°C, with further temperature increases leading to a considerable reduction in CO2 assimilation.

It has been extensively explored how the inherent mechanisms for reduced photosynthesis under high temperature stress work. First off, the bifunctional enzyme ribulose-bisphosphate carboxylase/oxygenase (Rubisco) can have its activity significantly reduced at supra-optimal temperatures. Additionally, as the temperature rises, ribulose-(RuBP) bisphosphate's ratio of oxygenation to carboxylation rates grows, leading to a faster rate of CO2 release by photorespiration. Third, the diffusion capacity is extremely sensitive to temperature, but the responses are species dependent. Second, the electron transport rate is significantly hindered at extremely high temperature stress, i.e., at 40°C. With rising temperatures, stomatal conductance (gs) and mesophyll conductance (gm) can rise, fall, or remain constant.

One of the most significant elements, nitrogen (N), can control leaf photosynthesis in a number of ways. First off, leaf photosynthesis is often positively correlated with leaf N content due to the significant contributions of leaf N to Rubisco, the electron transport proteins, and the major enzymes of the Calvin cycle. Second, under high N supply, gs and gm can both significantly increase. Increased chloroplast surface area facing intercellular air spaces (Sc) and decreased cell wall thickness are the main causes of the rise in gm under high N input. In addition, diminished photosynthetic sink capacity in N-limited plants can result in an accumulation of carbohydrates in the leaves, which will counteract photosynthesis. However, whether or not N supply influences how photosynthesis reacts to high temperatures is still unknown. Uncertainties surround stress.

In contrast to the extremely dynamic light settings found in crop canopies, photosynthesis is often researched under saturated and stable light conditions. Because of variations in the amount of incoming solar irradiance, wind, cloud cover, and self-shading of the upper leaves, leaves within crop canopies experience a light environment that is very changeable in magnitude and time throughout the course of a day. According to Pearcy et al., sun flecks make up 20–93% of the total daily photosynthetic photon flux density received. Photosynthesis is a complex process that cannot react to changes in irradiance linearly. Photosynthesis does not grow to its maximal rate when the irradiance changes from low to high levels because enzyme activation and stomatal opening take time. The light output is greatly reduced due to the inability of photosynthesis and variable irradiance to work together. Make good use of dynamic irradiance.

Little is known about how abiotic stressors affect dynamic photosynthesis. The effects of high CO2 concentration, water stress, air humidity, and nitrogen availability on dynamic photosynthesis have only been briefly examined in a few pieces of research. More research in this area is required to comprehend photosynthesis in its natural setting. High temperatures can limit the photosynthetic carbon gain during light flecks, which are very brief but intense patches of light that can temporarily boost leaf temperature. To the best of our knowledge, just one study has looked into how high temperatures affect dynamic photosynthesis. In a tropical rain forest tree seedling called Shorea leprosula, it is shown that high temperature inhibition of photosynthesis is more severe under sunflecks than it is under uniform irradiance. In contrast, whether and how unknown factors influence how dynamic photosynthesis reacts to extreme temperature stress is still unclear.