Effect of levels of water stress on some physiological and chemical traits of wheat cultivars (Triticum aestivum L.)

Abstract

A field experiment was carried out at the second agricultural experiment station of the College of Agriculture - Al-Muthanna University during the agricultural season of 2022-2023. The objective of the study was to investigate the physiological and chemical responses of different bread wheat varieties to incomplete irrigation. The experiment was conducted utilising the randomised complete block design (RCBD) employing the split plot method, with three replications. The primary factors investigated in this study were related to irrigation deficiencies, which were represented by four different stages: D1 (control), D2 (tillering stage), D3 (elongation stage), and D4 (booting stage). The secondary factors examined in this research were different cultivars, denoted as V1 (Mawadah), V2 (Bohuth 22), V3 (Baraka), and V4 (Ibaa 99). The statistical analysis revealed significant variations among the stages of water stress. The D2 treatment exhibited the highest proline content at 41.692 mg per 100g, while the D4 treatment demonstrated the greatest thickness of vascular bundles in the roots at 201.23 μm. Regarding the cultivars under investigation, it was observed that the Baraka variety exhibited a higher chlorophyll content (54.24 SPAD units). In contrast, the Bohooth22 cultivar displayed a larger diameter of the vascular bundle in the roots (209.78 μm). Additionally, the Mawada variety demonstrated a greater thickness of the leaf vascular bundles (102.38 μm), while the cultivar IPA99 exhibited a higher content of Proline (35.481 mg per 100g). In terms of interference, treatment D3V1 exhibited a higher proline content of 48.607 mg/100g, indicating its superiority. The results of histological analysis showed the superiority of the combination D2V1 in the diameter of the vascular bundles of the roots (247.33) micrometers, and the occurrence of rupture and damage in the cells of the basal tissue of the root tissue in (D2V1, D3V1, D3V2) and in (D2V1, D2V2, D3V2), in addition to the occurrence of rupture and damage in the upper and lower epidermal cells in the tissue of its leaves, while the combination D2V3 wrinkled and damaged mesophyll cells, and excelled in the thickness of the leaf vascular bundles (142.40) µm, as well as showed that detachment and rupture of the upper epidermis from the mesophyll occurred in D2V4. The results of histological cutting of root cells showed that bundle damage appeared in the root tissue of combination D3V3. Also, fracture and separation occurred in the region of the vascular bundle from the underlying tissue, and some wood vessels were also damaged in the root tissue of the treatment D4V1, and in D4V3 there was a rupture in the lower epidermis of the leaf tissue, and a break in the cells of the cortex and epidermis of the root tissue, while in D4V4, damage was observed in the bundle and cells of the cortex, in addition to the occurrence of a tear in the lower epidermis of the leaves.