Nitrogen supply enhances the physiological resistance of Chinese fir plantlets under polyethylene glycol (PEG)-induced drought stress

Abstract

Water and nitrogen stresses are major constraints for agricultural and forest productivity. Although the effects of water scarcity or nitrogen stress on plant growth, physiology, and yield have been widely studied, few studies have assessed the combined effects of both stresses. In the present study, we investigated the effects of different nitrogen forms (NO3−N, NH4+-N, and a combination of NO3−N + NH4+-N) on antioxidant enzyme activity, osmotic regulatory substances, and nitrogen assimilation in Chinese fir (Cunninghamia lanceolata) plantlets under drought stress (induced by 10% polyethylene glycol). We found that different N ionic forms had different effects on drought-stressed plantlets. Nitrogen supply greatly increased the activities of superoxide dismutase (SOD), peroxidase (POD) and polyphenol oxidase (PPO) when plantlets were exposed to water stress. The malondialdehyde (MDA) contents significantly decreased under the NH4+ + water stress treatment. The proline (Pr) contents significantly increased in both the NO3−N and NH4+-N + water stress treatment. The nitrate reductase (NR) increased by 7.1% in the NO3− + water stress treatment, and the glutamine synthetase (GS), and the glutamate synthase (GOGAT) activity increased in all the nitrogen + water stress treatments. These results suggested that nitrogen supply could alleviate the adverse effects of drought stress on plants by enhancing antioxidant defense and improving nitrogen assimilation, while the effects on plant tolerance to drought stress varied with nitrogen ionic forms.

Tracing the acclimation of European beech (Fagus sylvatica L.) populations to climatic stress by analyzing the antioxidant system

“…The tendency was the same with PPO enzyme, yet correlation relationships were not significant. Normally, oxidative stress triggers an increase of POD levels in tree leaves (Boughalleb & Mhamdi 2011, Chakhchar et al 2015a, 2015b, Song et al 2015 while the changes of PPO activity are variable, depending on species, stress tolerance, and circumstances (Vahdati & Lotfi 2013, Song et al 2015, Li et al 2020. According to the correlation between POD vs. stem diameter, a decrease of activity in the provenances with lower stem diameters was experienced, which together with the generally lower tree vigor and higher tree mortality rate indicates that their long-term acclimation has not been successful, leading to decreased enzyme activities in the exhaustion phase of the stress response (Selye 1950).…”

Nitrogen supplement attenuates drought stress for non‐leguminous hybrid plant fescue and does not affect nitrogen‐fixing alfalfa

“…Correlation between drought tolerance and antioxidant enzyme activity was found by many scientists and suggests that plants have efficient ROS removal and signalling system (Li et al, 2020). Flavonoids are one of the major classes of plant phenols that participate in plant protection (Kirova et al, 2021).…”

Drought stress mitigation by nitrogen in boreal forests inferred from stable isotopes

“…Therefore, though the influence of N on both g s and A max might have become effective, it is likely that the control of g s was more relevant to influence growth variability of the L. sibirica stemwood. Moreover, an improved N supply could also enhance the trees' capability for osmotic adjustment by boosting free amino acid production (Li et al, 2020) and intensify the defence against herbivores and pathogens (Simon et al, 2010). In addition to amino acids (especially proline: Hayat et al, 2012;Vance & Zaerr, 1990), nitrate ions also serve as osmolytes (Cárdenas-Navarro et al, 1999).…”