Abstract
Maize belongs to a tropical environment and is extremely sensitive to drought and chilling stress, particularly at early developmental stages. The present study investigated the individual and combined effects of drought (15% PEG-Solution) and chilling stress (15/12 °C) on morpho-physiological growth, osmolyte accumulation, production of reactive oxygen species (ROS), and activities/levels of enzymatic and non-enzymatic antioxidants in two maize hybrids (i.e., “XD889” and “XD319”) and two inbred cultivars (i.e., “Yu13” and “Yu37”). Results revealed that individual and combined exposure of drought and chilling stresses hampered the morpho-physiological growth and oxidative status of maize cultivars, nevertheless, the interactive damage caused by drought + chilling was found to be more severe for all the studied traits. Between two individual stress factors, chilling-induced reductions in seedling length and biomass of maize cultivars were more compared with drought stress alone. Greater decrease in root length and biomass under chilling stress ultimately decreased the volume and surface area of the root system, and restricted the shoot growth. All the stress treatments, particularly chilling and drought + chilling, triggered the oxidative stress by higher accumulation of superoxide anion, hydrogen peroxide, hydroxyl ion, and malondialdehyde contents compared with the control. Variations in response of maize cultivars were also apparent against different stress treatments, and XD889 performed comparatively better than the rest of the cultivars. The better growth and greater stress tolerance of this cultivar was attributed to the vigorous root system architecture, as indicated by higher root biomass, root surface area, and root volume under drought and chilling stresses. Moreover, efficient antioxidant defense system in terms of higher total antioxidant capability, superoxide dismutase, peroxidase, catalase, and glutathione reductase activities also contributed in greater stress tolerance of XD889 over other cultivars.
Highlights
Crop plants often experience multiple abiotic stresses simultaneously, of which concurrent effects of sub-optimal temperature and moisture deficit conditions are perhaps the most deleterious for Plants 2020, 9, 720; doi:10.3390/plants9060720 www.mdpi.com/journal/plantsPlants 2020, 9, 720 plant growth [1,2,3]
All the stress treatments significantly (p < 0.05) reduced the shoot fresh weight and stem diameter of maize cultivars compared with the control, except the stem diameter of Yu13 and Yu37 was unaffected by chilling stress
Individual and concurrent exposure of drought and chilling stresses hampered the morpho-physiological growth and oxidative status of maize cultivars, the interactive damage caused by drought + chilling was found to be severe for all the studied traits
Summary
Crop plants often experience multiple abiotic stresses simultaneously, of which concurrent effects of sub-optimal temperature and moisture deficit conditions are perhaps the most deleterious for Plants 2020, 9, 720; doi:10.3390/plants9060720 www.mdpi.com/journal/plantsPlants 2020, 9, 720 plant growth [1,2,3]. Drought and chilling stresses cause substantial reductions in growth and yield attributes of plants by disturbing normal plant metabolism [2,4]. Sub-optimal temperature causes water deficiency in maize seedlings by substantial reduction in root water uptake coupled with leaves transpiration [5]. Hussain et al (2018) concluded that the both drought and chilling stresses disrupt the plant–water relations, but these effects are possibly more detrimental under the simultaneous occurrence of these both factors [2]. Chilling stress was found to decrease the root growth of maize seedlings by decreasing the length and biomass of the roots [7], in contrast, drought stress increased the root length of sunflower plants but decreased later on with an increase in drought period [8]. Previous investigations have shown that the osmotic balance of the plants is more affected by drought as compared to chilling stress [9]
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