Physiological and Anatomical Features of Two Triticum dicoccoides Wheat Accessions Differing in Photosynthetic Rate

Abstract

The wild tetraploid species Triticum dicoccoides (L.) Korn has many traits that may be useful to hexaploid wheat (T. aestivum L.). Two accessions of this species (PI 428042 and PI 428109) were found have similar‐sized leaves, but they differ by ≈30% in net CO2 assimilation per unit leaf area (A). We sought to identify physiological and anatomical factors that would explain the difference in photosynthetic rate between the two accessions, and between these accessions and the hexaploid wheat ‘TAM W‐101’. Photosynthetic responses to CO2 (at 20 and 210 mL O2 L−1 air), light, and humidity, and also ribulose bisphosphate carboxylase (rubisco) activity and sucrose concentration, were determined on new fully expanded leaves of each genotype. Anatomical features associated with photosynthesis were determined using light and electron microscopy. PI 428109 showed consistently higher A than PI 428042 at varying levels of CO2, light, and humidity. Higher rubisco activity was observed in leaves of PI 428109 than PI 428042, as also indicated by a greater slope of the initial linear portion of the A vs. ci (intercellular leaf CO2 concentration) curve. A higher sucrose concentration was observed in the leaves of PI 428042 than in PI 428109. No anatomical differences were detected between the two T. dicoccoides accessions. Therefore, photosynthetic differences between the two T. dicoccoides accessions were biochemically, and not anatomically, driven.