Daily Fluctuations of Some Metabolic Characters of Durum Wheat under Field Conditions

Abstract

Physiological and biochemical parameters have been studied simultaneously with micrometeorological characters of a crop of durum wheat (Triticum durum). Micrometeorological measurements and plant analysis on flag leaves before spike appearance were done during 2 days in May 1973 to ascertain the fluctuation of chosen leaf parameters in comparison with the micrometeorological ones. The results indicate that biochemical and physiological changes occur during the day and night and that stomatal opening is the main factor dependent on climatic conditions. Specific leaf weight (SLW) seems to vary with the level of free amino acids. Ribulose diphosphate carboxylase (RuDPcase) showed daily fluctuations insensitive to climatic conditions, whereas phosphoenolpyruvate carboxylase (PEPcase) exhibited little day change.

Light Activation of Ribulose Bisphosphate Carboxylase

“…In summary: (a) the UV activation effect on RuBPCase has been demonstrated here and elsewhere (2,12,13,33,34) as an in vitro phenomenon; (b) appropriate UV chromophores have sometimes been demonstrated to be associated by activity (33) or physical evidence (7) with RuBPCase; (c) the natural environmental irradiation contains such long wavelength light at more than adequate intensities (25,26); and (d) in vivo information that supports the existence of this phenomenon is available (14,15 …”

“…3B) (14,15). DiMarco et al (14) measured CO2 plus RuBP-dependent 3-PGA synthesis rates of wheat leaf extracts. The ability of these extracts to synthesize 3-PGA varied with the time of day.…”