Comparison of Ion Balance and Nitrogen Metabolism in Old and Young Leaves of Alkali-Stressed Rice Plants

Abstract

BackgroundAlkali stress is an important agricultural contaminant and has complex effects on plant metabolism. The aim of this study was to investigate whether the alkali stress has different effects on the growth, ion balance, and nitrogen metabolism in old and young leaves of rice plants, and to compare functions of both organs in alkali tolerance.Methodology/Principal FindingsThe results showed that alkali stress only produced a small effect on the growth of young leaves, whereas strongly damaged old leaves. Rice protected young leaves from ion harm via the large accumulation of Na+ and Cl− in old leaves. The up-regulation of OsHKT1;1, OsAKT1, OsHAK1, OsHAK7, OsHAK10 and OsHAK16 may contribute to the larger accumulation of Na+ in old leaves under alkali stress. Alkali stress mightily reduced the NO3 − contents in both organs. As old leaf cells have larger vacuole, under alkali stress these scarce NO3 − was principally stored in old leaves. Accordingly, the expression of OsNRT1;1 and OsNRT1;2 in old leaves was up-regulated by alkali stress, revealing that the two genes might contribute to the accumulation of NO3 − in old leaves. NO3 − deficiency in young leaves under alkali stress might induce the reduction in OsNR1 expression and the subsequent lacking of NH4 +, which might be main reason for the larger down-regulation of OsFd-GOGAT and OsGS2 in young leaves.Conclusions/SignificanceOur results strongly indicated that, during adaptation of rice to alkali stress, young and old leaves have distinct mechanisms of ion balance and nitrogen metabolism regulation. We propose that the comparative studies of young and old tissues may be important for abiotic stress tolerance research.

Signal Perception and Mechanism of Salt Toxicity/Tolerance in Photosynthetic Organisms: Cyanobacteria to Plants

“…Plant's response to salt not only varies with crop varieties or cultivars but also with the age. For example, in rice older leaves are reported to accumulate higher nitrate content than the younger ones probably because of an upregulated nitrate transporter OsNRT1;2 (Wang et al 2012). Since many cyanobacterial species are endowed with the N 2 -fixing ability, it is relevant to study the effect of high salt on N 2 fixation in general and nitrogenase in particular.…”

Global proteomic mapping of alkali stress regulated molecular networks in Helianthus tuberosus L.

“…Countable studies of the basic physiological mechanisms of the alkali stress response were conducted in several plant species including crops and halophytes during recent years. The metal element (K, Ca, Mg, Fe, Cu, Zn) and free ions (NO 3 -, Cl -, H 2 PO 4 -, SO 4 2-) content was decreased in alkali treated plants such as wheat, rice and seabuckthorn, suggesting that high pH stress inhibits the nutrient absorption and disturbs ion balance in plants (Chen et al 2009;Wang et al 2012;Guo et al 2015). Studies have shown that alkali stress also significantly affects photosynthesis and photosynthetic electron transport.…”

Superexpressão do transportador OsNPF4.11 (OsNRT1.2) afeta teor de nitrato, parâmetros radiculares e crescimento de arroz

“…Ao contrário da expressão induzida pelo nitrato do NRT1.1, o RNA mensageiro do AtNRT1.2 acumula mesmo na ausência de nitrato, demonstrando ser um componente constitutivo do LATS (Dechorgnat et al, 2011 (Wang et al, 2012a).…”