Rates of photosynthesis in leaves of wheat and barley varieties.

Abstract

In 18 cultivars of spring wheat the range of difference in rate of photosynthesis of leaves was 22% (range 325-414 mg co2/cm2h), and in 12 cultivars of spring barley the difference range was 20% (range 284-366 mg CO2/cm2h). Measurement difficulties were initially found because of a high degree of variability within cultivars, but these were partly resolved by improving the conditions under which the plants were grown. Rates of photosynthesis reached a maximum in leaves that had attained their ultimate area, and then decreased gradually with ageing of the leaves. No evidence was found for regulation of photosynthesis by the demand for assimilates; photosynthetic capacity was determined mainly by leaf age. Low N supply and the resulting low protein content of leaves reduced the rate of photosynthesis. In leaves of a given age, but not in leaves of different ages, rate of photosynthesis was correlated with leaf protein content. (Abstract retrieved from CAB Abstracts by CABI’s permission)