Effects of drought stress and subsequent rewatering on major physiological parameters of spring maize during the key growth periods

Abstract

For deeply understanding water consumption characteristics and disaster-causing mechanism of spring maize under drought stress, continuous no-water complementing for 40 days and subsequent rewatering treatments were conducted in jointing (T1) and tasseling (T2) stages of spring maize 'Danyu 39'. In the meantime, leaf and root water potential, main variables associated with photosynthesis including net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conduc-tance (gs), intercellular CO2 concentration(Ci) and stem flow rate (SF) were dynamically observed and the characteristics of their responses to drought and subsequent rehydration were investigated. The results indicated that leaf and root water potential, both presenting logarithm relationships with soil water content, decreased due to suffering from drought stress in different growth stages and the response of the former lagged behind that of the latter. At the same time, the response of leaf (root) water potential to drought stress in tasseling stage was earlier (later) than in jointing stage. For the response of rewatering, leaf water potential for the treatment T1(T2) was (not) able to recover to a certain extent, and could not reach the normal condition, while water potential of root was more responsive and closer to the normal level than that of leaf for the treatment T1. Furthermore, Pn and Tr responded more quickly to the treatment T2 than to the treatment T1. For subsequent rewatering after the treatment T1(T2), both Pn and Tr restored rapidly (slowly) with the former exceeding (returning) and the later being (not) able to reach normal level. Meanwhile, the response of Tr was faster than that of Pn to the treatment T1 and they responded simultaneously to the treatment T2. The response of gs agreed with Pn to drought stress. Change trend of Ci for the treatment T1(T2) was consistent (opposite) with that of Pn. In addition, SFs for various drought treatments and their daily maximums decreased and appeared ahead of time to different extents, respectively. At the same time, the response of SF to drought stress was more sensitive for the treatment T2 than for T1 and on a clear day than on a cloudy day, but the sensibility of SF declined after drought reached a certain level. Besides, SFs for both the treatment T1 and T2 increased as a result of rewatering after drought and the increase for the treatment T1 was larger than that for the treatment T2.