Correlations among leaf CO2-exchange rates, areas and enzyme activities among soybean cultivars

Abstract

Soybean (Glycine max (L.) Merr.) genotypes varying in area per nodal unit (usually a trifoliolate) and maturity class were grown in plots at the University of Illinois experimental farm. Leaf CO2-exchange rates per unit area (CER) were measured under sunlight on intact plants. In addition to previously reported correlations with specific leaf weight and chlorophyll, CER was positively correlated with ribulose bisphosphate carboxylase (RuBPcase) activity, specific activity, and soluble protein, and was negatively correlated with area per leaf unit. The CER: chlorophyll correlation was destroyed by high CER values in 2 chlorophyll-deficient lines. CER values for 27 of the 35 lines tested fell within the range of those for isolines of cultivar Clark varying in leaf characteristics. The CER values were highest for fully expanded leaves during rapid pod fill. These results suggested that photoperiod (maturity) genes and genes for leaf area growth interact with genes controlling photosynthetic CO2-exchange to produce the major differences in CER values among soybean genotypes.

Activation State of Ribulose Bisphosphate Carboxylase in Soybean Leaves

“…2), essentially free of all Chl, thus eliminating the possibility that inhibition may have occurred because of a binding of RuBPCase to chloroplast membranes (16). This inhibition of soybean RuBPCase by high Mg24 is insignificant as regards assay because the enzyme is approximately 94% activated by 5 mM Mg2e in the presence of 20 mm NaHCO3 (Fig. 2) (19).…”

“…This irreversible loss of activity with time is probably the result of protease action rather than progressive inhibition by small mol wt compounds present in the leaf extract. Extracts of soybean leaves are known to contain a number of endoproteases which can rapidly degrade the large subunit RuBPCase (21) (5,18). There are at least two reasons for this apparent inconsistency.…”

Genetic Variation in Biomass Traits among 20 Diverse Rice Varieties

“…We found a negative correlation between photosynthetic CO 2 assimilation rates and biomass accumulation in the OryzaSNP set. Although counterintuitive, this result is not unique to rice; strong negative correlations have been observed between photosynthetic rates and total leaf area in field-grown soybean (Glycine max; Hesketh et al, 1981) and among photosynthetic rates and leaf size in field-grown wheat and goatgrass (Aegilops spp. ; Austin et al, 1982).…”

Utility of basic research in plant/crop physiology in relation to crop improvement: a review and a personal account

“…Balakrishnan et al (1987), working with several pigeon pea cultivars growing in the field during three different seasons in India, found significant positive correlations between leaf photosynthetic rates and total dry matter and seed yield, when photosynthesis was measured at the first flowering phase. Hesketh et al (1981) evaluated leaf photosynthesis behavior in the field in the USA, for a large group of soybean genotypes varying in area per nodal unit and maturity classes. They measured CO 2 exchange rate per unit leaf area (CER) under high photon flux density on intact plants, as well as the activity of the C 3 enzyme Rubisco.…”