Ear of durum wheat under water stress: water relations and photosynthetic metabolism

Abstract

The photosynthetic characteristics of the ear and flag leaf of well-watered (WW) and water-stressed (WS) durum wheat (Triticum turgidum L. var. durum) were studied in plants grown under greenhouse and Mediterranean field conditions. Gas exchange measurements simultaneously with modulated chlorophyll fluorescence were used to study the response of the ear and flag leaf to CO2 and O2 during photosynthesis. C4 metabolism was identified by assessing the sensitivity of photosynthetic rate and electron transport to oxygen. The presence of CAM metabolism was assessed by measuring daily patterns of stomatal conductance and net CO2 assimilation. In addition, the histological distribution of Rubisco protein in the ear parts was studied by immunocytochemical localisation. Relative water content (RWC) and osmotic adjustment (osmotic potential at full turgor) were also measured in these organs. Oxygen sensitivity of the assimilation rate and electron transport, the lack of Rubisco compartmentalisation in the mesophyll tissues and the gas-exchange pattern at night indicated that neither C4 nor CAM metabolism occurs in the ear of WW or WS plants. Nevertheless, photosynthetic activity of the flag leaf was more affected by WS conditions than that of the ear, under both growing conditions. The lower sensitivity under water stress of the ear than of the flag leaf was linked to higher RWC and osmotic adjustment in the ear bracts and awns. We demonstrate that the better performance of the ear under water stress (compared to the flag leaf) is not related to C4 or CAM photosynthesis. Rather, drought tolerance of the ear is explained by its higher RWC in drought. Osmotic adjustment and xeromorphic traits of ear parts may be responsible.

Precision Planting Patterns Effect on Growth, Photosynthetic Characteristics and Yield of Winter Wheat under Deficit Irrigation

“…This variation may be due to leaf assimilation ability restrained with vegetative growth at jointing stage, but the nutrient in the vegetative organs start to transport for reproductive growth, thus leaf assimilation ability raise. Tambussi et al (2005) indicated that the photosynthesis after anthesis and during grain filling play important role for the final grain yield. The wide-narrow planting pattern improved leaf photosynthesis by changing the local farmland microclimate (Fernado et al, 2002).…”

Moving micronutrients from the soil to the seeds: Genes and physiological processes from a biofortification perspective

“…Siliques have stomata [105] and carry out photosynthesis [106], and apparently transpire [107], as do glumes of wheat [108,109]. Thus, the potential for xylem transport of micronutrients directly to these seed covering tissues exists.…”

Differences in the drought stress response ofDREB2andCAT1genes and evaluation of related physiological parameters in some bread wheat cultivars

“…Then the leaves were quickly and carefully dried with filter paper to determine turgid weight (TW). Dry weight (DW) was obtained after oven-drying the leaf samples for 72 h at 70 C. RWC was calculated from the equation of Tambussi et al [25]:…”