A physiological Explanation of Drought Effect on Flag-Leaf Specific Weight and Chlorophyll Content of Barley

Abstract

This study was carried out in Kalar technical institute, Sulaimani PolytechnicUniversity in Garmian region, Iraq during 2016-17 and 2017-18 seasons. Fivehybrid genotypes of barley were tested under drought and irrigated conditions todetect the flag-leaf specific weight, chlorophyll content index (SPAD; The SoilPlant Analysis Development chlorophyll meter) and the period from anthesis tophysiological maturity. Across both years 2016-17 and 2017-18, there was no effectof drought on flag-leaf specific weight, however, SPAD was reduced by 4.77 andthe period between anthesis and maturity was shortened by almost two days.Genotype 3//14 scored the highest values of flag-leaf specific weight (7.765 mg cm-2)and SPAD (25.56), and stayed green for the longest period (28.69 days) (P=0.05),showing its ability to be more tolerant to moisture reductionas compared to the othertested genotypes. In order to explain the physiological mechanisms among theassessed traits under both irrigated and drought conditions, linear regression analysiswas applied for both seasons and averaged over seasons. A positive linearrelationship was shownbetween flag-leaf specific weight and SPAD under bothirrigated (R2=0.83; P=0.03) and drought (R2=0.76; P=0.05) conditions, explainingthe high flag-leaf chlorophyll content resulting from high specific weight of leaves.The high flag-leaf specific weight was also associated with longer periods for leavesto stay-green after anthesis, under both irrigated (R2=0.91; P=0.01) and drought(R2=0.79; P=0.04) conditions, which provides a great chance to accumulate moreresources of carbohydrates and protein in the grain and, consequently,a higherthroughput of yield.