Mature Tissue and Crop Canopy Respiratory Characteristics of Rye, Triticale and Wheat

Abstract

Crop dry matter and its chemical composition, together with canopy and mature tissue respiration rates were measure at equivalent growth stages and temperatures for spring and winter rye, triticale and wheat crops grown under irrigated field conditions. Canopy respiration was partitioned into growth and maintenance respiration using information from the chemical composition analysis of the crop biomass. Rates of dry matter accumulation early in the growing season were significantly greater for rye crops in comparison to triticale and wheat. However, when dry matter was measured at similar ontogenetic stages, the productivity advantage of the rye crop was no longer evident. Nevertheless, canopy respiration rates per unit ground area were significantly lower for rye than wheat over all temperatures and growth stages. Intergeneric differences in the respiration rates of mature leaf and stem tissues were consistent with those measured at canopy scales. Differences in the chemical composition of the biomass among genera were minimal, and insufficient to account for differences in canopy respiration due to synthesis respiration requirement. Estimates of biomass maintenance requirements appear to be significantly lower for rye than wheat when calculated at similar temperatures and ontogenetic stages. The maintenance coefficient (m) depended on stage of development, suggesting that m will decline earlier chronologically for rye than wheat, which implies that greater carbon retention is another aspect contributing to the higher early-season crop growth rates of spring and winter rye. Considering the lower respiration rates of mature stems relative to leaves, the dependence of m on stem:leaf ratio was suggested as a useful approach to modelling ontogenetic effects on maintenance respiration.Copyright 1993, 1999 Academic Press