Dry-matter yield, protein synthesis, starch, and fiber content of barley and wheat plants under two irrigated regimes

Despite the voluminous literature available on the influence of stress on plant growth and development, the issue is still controversial. The purpose of the present investigation was to gather further information on the effects of water deficit on two main agronomic crops, barley and wheat, in a region with a relatively insufficient research history. Dry-matter yield of straw and grains, protein content, starch, fiber, and ash percentage of barley (Hordeum vulgare L., cv. 'Walfajr') and wheat (Triticum aestivum L., cv. 'Karaj I') under two irrigation regimes were studied at the College of Agriculture, University of Tehran Experimental Farm, located in the city of Karaj, Iran. The treatments consisted of two irrigation regimes, at 7 d intervals (control) and 14 d intervals (stress). Total dry-matter yields of straw and grains of both species decreased under stress. Nevertheless, the fluctuation in dry-matter percentage (DM%) of both plants and the plant parts was not significant (ranging from 91.3-92.5). The ash percentage of the straw was about twofold that for the grains for both plants. The fiber acid detergent fiber (ADF) and neutral detergent fiber (NDF) percentage of straw was substantially higher than that for the grains for both species. The crude protein (CP) concentration of the grains was markedly higher than that for the straw under both irrigation regimes. Although the CP concentration of the stressed plants was numerically higher than that for the controls, this difference was not statistically significant. On the other hand, the total CP content of both plant parts decreased appreciably as irrigation intervals increased. This pattern was essentially similar for both plants. Total starch percentage of both species was significantly higher under stress conditions. Comparing the two species, wheat grains had a substantially higher percentage of starch than did barley grains.