Exogenous application of trehalose alters growth, physiology and nutrient composition in radish (Raphanus sativus L.) plants under water-deficit conditions

Radish (Raphanus sativus L.) is one of the most desirable vegetables grown in many parts of the world due to its short growth period and high nutritious value. To explore its cultivation in rain-fed areas, the present study was conducted to assess the role of foliar-applied trehalose (25 and 50 mM) in two radish cultivars, Manu and 40-days, grown under non-stress (100 % FC) and water stress (60 % FC) conditions. Under drought stress conditions, shoot fresh and dry weights, shoot and root lengths, photosynthetic rate (A), transpiration rate (E), stomatal conductance (g(s)), internal CO2 concentration (C-i), relative water contents (RWC), shoot K+ and P and shoot and root Ca2+ decreased, while water-use efficiency (WUE) and relative membrane permeability (RMP) increased in both radish cultivars. External fortification with trehalose improved shoot fresh and dry weights, chlorophyll a content and accumulation of P in shoot, but decreased RMP in both cultivars. However, trehalose application caused no significant alteration in shoot and root lengths, A, chl. b content, C-i, WUE and RWC. Of both radish cultivars, cv. 40-days excelled cv. Manu in shoot fresh weight, shoot length, E, g(s), C-i, WUE and shoot K+ and Ca2+, whereas the reverse was true for A and RMP. Overall, water stress adversely affected growth and other physiological attributes appraised, but foliar-applied trehalose improved only growth and shoot P and decreased RMP. The relatively better growth of cv. 40-days could be due to trehalose-induced physio-biochemical attributes other than those measured in the present study except trehalose-induced improvement in shoot P and reduction in RMP. Therefore, a further study needs to be carried out to find out the role of trehalose on attributes which are directly or indirectly involved in plant growth under stress conditions.