Respiration of Some Herbaceous Plants at Different Temperatures and Its Relation to Growth

Abstract

The respiration for Ageratum houstonianum 'Capri', Calendula officinalis 'Dania', Scabiosa atropurpurea 'Imperial', and Tagetes patula var. nana 'Naughty Marietta' was examined manometrically in multithermostat at temperatures from 0 to 30'C. Within this temperature range the respiration increased more than linearly with the temperature, but slowest for Scabiosa. The regression equations y = a + bt2 gave a satisfactory expression for the respiration (see Figs. 2a-d). The respiration intensity at the various temperatures varied considerably for the cultivars. At 0C higher respiration was found for Calendula and Scabiosa than for Tagetes and Ageratum; at 30'C the respiration was highest for Tagetes and Calendula. The relative respiration with 10C chosen as a standard equal to 1.00 was for Calendula similar to values for spruce and pea reported by Dahl and Mork (Tab. 3). Above 15'C the deviations from these values were considerable for Ageratum and Tagetes. Still greater deviations from spruce and peas were found for Scabiosa. Correlations between growth and temperature data for the cultivars in the second growth phase were compared with correlations between growth data and calculated respiration sums according to the regression equations in the same growth period. By experiments in constant climate the elongations were also correlated with respiration equivalents calculated for corresponding periods as the other data. Higher correlation coefficients were in constant climate usually found for elongation correlated with one of the respiration measures than with the temperature itself. It suggests that respiration was one of the most important growth limiting factors under these conditions. In field experiments, however, highest correlation between growth data and calculated respiration sums was usually obtained only after exclusion of the experimental plots with highest temperatures.