The Effect of Temperature on the Growth of Cocksfoot (Dactylis glomerata L.)

The growth of cocksfoot at 14°, 22°, and 26° C wasmeasured at weekly intervals over a period of six weeks. Initially,the relative growth rates increased with increase in temperature,but during the final three weeks they were little differentat all three temperatures. The reduction in relative growthrates with time at 22° and 26° were associated withincreases in size which were partly reflected by reductionsin the leaf-area ratios. It is also likely that at 26° changesin the photosynthetic capacity of leaves, perhaps associatedwith decreasing concentrations of mineral nutrients, contributedto the decreased relative growth rates. Leaf expansion and increase in cell numbers were estimated overtwo-day periods at temperatures ranging from 5° to 30°C. Leaf expansion increased with increase in temperature throughoutthis range; extrapolation suggested that it would cease at temperaturesbelow 3° C. The optimum temperature for cell division appearedto be between 20° and 25°C. Different physiological processes appeared to be involved inthe temperature responses of plants of different sizes and histories.With young plants these responses resulted in a large overalleffect of temperature on the growth rate; with older plantsof the same size there appeared to be several compensatory responsesso that variation in temperature over an apprecaible range hadlittle overall effect.