Drought Response of wheat (Triticum Aestivum L.) Cultiv ars Grown under Field Stress

Abstract

A field experiment was carried out to study the physiological analysis of drought response of five wheat cultivars viz., Sonalika, Kanchan, Aghrani, Akbar and Barkat. The two moisture levels were irrigation at three times ( 1 0 mm on each occasion) during the whole growing period and rainfed control. The total amount of water received as irrigation was 30 mm anð€€¥ as rainfall 126 mm. Significant effects of soil moisture on total dry matter (TDM) and leaf area index (LAJ) was observed. The cultivars grown under irrigated condition had higher TDM and LAI than those grown under rainfed condition. TDM increased slowly at the early growth stages but increased sharply at the later growth stages. In all the five cuJtivars and in both the treatments starting from a lower value LAI increased with increasing plant age and reached a certain peak and then declined gradually. Significant effects of soil moisture in most of the growth stages were observed in plant height and number of tillers per plant. In case of number of leaf per plant treatment effect was found to be non_­significant in most cases. Different growth attributes like relative growth rate (RGR), relative leaf growth rate (RLGR), leaf weight ratio (L WR) and leaf area ratio (LAR) starting from a maximum value declined rapidly with increasing growth period. Specific leaf area (SLA) showed no clear pattern but crop growth rate (CGR) was low at the early growth period and increased gradually and again declined with increasing growth period. Net assimilation rate (NAR) was also low at the early growth stages but increased gradually at the later period. RGR, RLGR, LAR, SLA, CGR and NAR were found higher in the· irrigated plants than those of the rainfed plants. Grain yield was found to be positively and significantly correlated with SLA at the pre-flowering stage, LAR at the post flowering and LA[ at both the pre and post­flowering stages under irrigated condition. The partial correlation coefficient between RGR and NAR after the elimination of the effects of LAR was found to be positively significant at the early growth stages. Percentages of dry matter (OM) accumulation in the leaves was found higher at the initial stage and gradually decreased with time. OM accumulation in the stem remained similar throughout the growing period. DM of panicle increased gradually with increasing growth period. The higher relative leaf water content (RL WC) was observed at 8 am and at the later part of the day it decreased gradually. On average, maximum RL WC was recorded for Aghrani and minimum for Sonalika. The cultivars under rainfed condition contained more chlorophyll b and praline than those of the irrigated condition. In the irrigated plants RL WC and time taken to stomatal closure were higher than the rainfed plants. Significant effect of soil moisture on stomatal · number and pore length of both the adaxial and the abaxial surfaces was not observed. But significant effect of cultivar was observed in case of stomatal number and thickness of flag leaf The analysis of regression coefficients of RGR, LAR and SLA and their components showed highly significant regression values in most cases except in RGR on NAR and LAR on NAR where negative regression values were obtained. Significant soil moisture effect was observed in 1000-grain weight, total dry matter and grain yield. Among the five cultivars, Aghrani gave significantly higher grain yield under both the irrigated and rainfed conditions. Aghrani also showed highest LAI, RGR and SLA. High praline accumulation and low transpiration rate in Aghrani might help to adapt to water stress.