Physiological determinants of genotypic differences in carbon isotope discrimination in potato grown in well‐watered conditions

Abstract

SummaryCarbon isotope discrimination (A), leaf conductance (gs), photosynthetic capacity, and plant growth were measured in well‐watered, glasshouse‐grown potato plants of clones from a cross made between diploid Solanum tuberosum and Solanum vernei. Clones showed significant differences (P < 0.001) in gs, Δ, stomatal density, root growth, and total dry matter production. Carbon isotope discrimination of genotypes was positively correlated (P < 0.001) with gs. There was no correlation between gs and stomatal density indicating that differences in gs reflected differences in stomatal aperture. Differences in rooting characteristics or in root/shoot ratio did not contribute to differences in gs or A. Genotypic differences in photosynthetic capacity were not statistically significant, and there was no correlation between A and photosynthetic capacity. Total dry matter production and A were positively correlated (P < 0.001) when differences in the time of plant emergence were included in the regression model.It is concluded that differences in A among potato genotypes is largely determined by gs, but confounding of gs and photosynthetic capacity reduces genotypic variation in A compared with that in gs. Total dry matter production is largely determined by processes other than carbon assimilation rate per unit area in individual leaves. Effective use of A as a character for selection in plant breeding depends on elucidating the effects that differences in stomatal characteristics have on crop production both in well‐watered and in water‐limited crops.