Abstract
The role of plant hormone abscisic acid (ABA) in plants under drought stress (DS) is crucial in modulating physiological responses that eventually lead to adaptation to an unfavorable environment; however, the role of this hormone in modulation of glycinebetaine (GB) metabolism in maize particularly at the seedling stage is still poorly understood. Some hydroponic experiments were conducted to investigate the modulation role of ABA on plant growth, water relations and GB metabolism in the leaves of two maize cultivars, Zhengdan 958 (ZD958; drought tolerant), and Jundan 20 (JD20; drought sensitive), subjected to integrated root-zone drought stress (IR-DS) simulated by the addition of polyethylene glycol (PEG, 12% w/v, MW 6000). The IR-DS substantially resulted in increased betaine aldehyde dehydrogenase (BADH) activity and choline content which act as the key enzyme and initial substrate, respectively, in GB biosynthesis. Drought stress also induced accumulation of GB, whereas it caused reduction in leaf relative water content (RWC) and dry matter (DM) in both cultivars. The contents of ABA and GB increased in drought-stressed maize seedlings, but ABA accumulated prior to GB accumulation under the drought treatment. These responses were more predominant in ZD958 than those in JD20. Addition of exogenous ABA and fluridone (Flu) (ABA synthesis inhibitor) applied separately increased and decreased BADH activity, respectively. Abscisic acid application enhanced GB accumulation, leaf RWC and shoot DM production in both cultivars. However, of both maize cultivars, the drought sensitive maize cultivar (JD20) performed relatively better than the other maize cultivar ZD958 under both ABA and Flu application in view of all parameters appraised. It is, therefore, concluded that increase in both BADH activity and choline content possibly resulted in enhancement of GB accumulation under DS. The endogenous ABA was probably involved in the regulation of GB metabolism by regulating BADH activity, and resulting in modulation of water relations and plant growth under drought, especially in the drought sensitive maize cultivar JD20.
Highlights
Plants are frequently exposed to a variety of abiotic stresses such as drought stress (DS), which hamper plant growth and crop productivity worldwide [1]
Twelve days of integrated root-zone DS (IR-DS) induced by PEG significantly caused a decline in the growth of seedlings of both maize cultivars
Significant correlations among GB metabolism parameters, dry matter (DM) production and leaf Relative water content (RWC) were evident in maize plants under DS, but no or less significant under control treatments (Table 2). These results show that contents of abscisic acid (ABA), GB and choline as well as betaine aldehyde dehydrogenase (BADH) activity could be used as potential selection criteria for drought tolerance in maize
Summary
Plants are frequently exposed to a variety of abiotic stresses such as drought stress (DS), which hamper plant growth and crop productivity worldwide [1]. Drought stress (DS) causes considerable yield reduction in most crops including maize. Plants sense and adapt to different stresses by altering their physiological metabolism, and growth pattern, and mobilizing various defense mechanisms [5]. It is well established that glycinebetaine (GB) accumulates in plants during their adaptation to various types of environmental stresses including drought [7,8]. Glycinebetaine, a quaternary ammonium compound, is a very effective compatible solute which is found in a wide range of crops [7]. One of GB accumulators, this compatible solute accumulates in leaves in response to water deficit [7,9]. Glycinebetaine has been reported to synthesize from its precursor choline by a two-step oxidation, via the intermediate betaine aldehyde
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
