Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings

Abstract

Abiotic stresses, including nitrogen stress (NS), can hamper photosynthesis and cause oxidative damage to plants. Upregulation of the antioxidative defense system and photosynthesis induced by exogenous glycinebetaine (GB) and humic acid (HA) can mitigate the inhibitory effects of NS on plants. In the present investigation, the beneficial effects of exogenously applied GB and HA were examined on growth, leaf N status, photosynthesis, lipid peroxidation, and activities of some key antioxidant enzymes in the seedlings of maize cv. Zhengdan 958 (ZD958) exposed to NS. NS caused a significant reduction in total dry matter of seedlings of ZD958, but both GB and HA proved effective in mitigating this inhibition, hence, the beneficial effects of GB being more pronounced than those of HA. NS led to a considerable decrease in leaf total N and endogenous GB contents, stomatal conductance (g s ), net photosynthetic rate (P n ), intercellular CO 2 concentration (C i ), and activities of two key C 4 photosynthesis enzymes phosphoenolpyruvate carboxylase (PEPCase) and ribulose-1,5-bisphosphate carboxylase (RuBPCase) as well as of superoxide dismutase (SOD) and peroxidase (POD). This treatment caused an increase in lipid peroxidation, but showed no effect on POD activity. Exogenous application of varying doses of GB resulted in a decrease in lipid peroxidation and C i , and an increase in leaf total N and endogenous glycinebetaine (EGB) content, P n , and activities of RuBPCase, PEPCase, SOD, and catalase (CAT) under NS. In contrast, application of different doses of HA resulted in a decrease in lipid peroxidation, an increase in P n , g s , and C i as well as SOD, CAT, and POD activities without increasing leaf total N and EGB content, and enhanced RuBPCase and PEPCase activities. The present study suggests that exogenous application of GB and HA can induce tolerance in maize plants to NS, but through the regulation of different mechanisms.

Exogenous DCPTA Ameliorates Simulated Drought Conditions by Improving the Growth and Photosynthetic Capacity of Maize Seedlings

“…The growth inhibition induced by the simulated drought stress in this study has previously been observed in maize 24 and other plant species 5 . The reduction in the root biomass may have arisen from root respiratory inefficiency 25 , and the reductions in the shoot biomass have been reported reductions in chlorophyll content, PSII function, transpiration rates and stomatal conductance as well as by the diminished activities of key enzymes involved in carbon dioxide fixation 24 , 26 , and these effects were also observed in the present study. Interestingly, the deleterious effects of the simulated drought conditions on maize seedling growth were partly counteracted by the DCPTA pretreatment (Table 1 ).…”

Effects of foliar application of glycine betaine and chitosan onPuccinellia distans(Jacq.) Parl. subjected to salt stress

“…GB has a well-documented effect as osmoprotectant, and maintaining a better water status allows greater gas exchange levels and photosynthesis, and higher turgor driving cell expansion and shoot growth. Furthermore, GB application has been reported to increase leaf nitrogen content (Zhang et al, 2014), thus contributing to growth enhancement. Indeed, foliar application of GB resulted in higher levels of fresh biomass, due to greater tissue water content of the shoots, which can reduce the toxic effects of high levels of NaCl (Marcum & Murdoch, 1990).…”

EFFECT OF ASCORBIC, HUMIC AND NICOTINIC ACIDS ON CERTAIN BIOCHEMICL CONSTITUENTS IN FENUGREEK (Trigonella foenum-graecum L.)

“…HA was reported to positively influence net photosynthesis along with enhancing chlorophyll percentage and stomatal conductance (Tahir et al, 2013). In addition, the activity of two key photosynthetic enzymes, phosphoenolpyruvate carboxylase and ribulose-1,5-bis phosphate carboxylase was enhanced in response to HA treatment (Zhang et al, 2014). Total sugars, total free amino acids and protein concentrations were increased in snap bean treated with HA (Hanafy et al, 2010).…”