The effect of daylength and temperature on introduced legumes and grasses for the tropics and subtropics of coastal Australia. 1. Dry matter production, tillering and leaf area

Abstract

Primary growth and regrowth at 28-day intervals of 20 tropical grasses and tropical and temperate legumes were measured in controlled environments. The treatments were : 1 : daylength 14 hours-day/night temperatures 32¦/24¦C ; 2 : 14 hours-26¦/15¦C ; 3 : 11 hours-26¦/15¦C; 4 : 11 hours- 20¦/6¦C. Regimes 1 and 4 represent the daylength and mean maximum and minimum temperatures of mid summer and mid winter in southern Queensland, respectively. Regimes 2 and 3 were included to separate daylength from temperature effects and 26¦/15¦C is close to April and October maximum/minimum temperatures. The grasses and the temperate legumes were less affected by these treatments than the tropical legumes, many of which died in regime 4. The best tolerance to regime 4 in relation to regrowth in regime 1 or 2 was exhibited in the following order by Trifolium repens, Medicago sativa, Lotononis bainesii, T. semipilosum, Chloris gayana and Paspalum dilatatum. The worst affected was Centrosema pubescens. A reduction in daylength from 14 to 11 hours at 26¦/15¦C resulted in less regrowth for Macroptilium atropurpureum and Desmodium intortum and in more tillering in most grasses. The most cold tolerant grasses, C. gayana and P. dilatatum had the highest tiller numbers in regime 4. The grasses and all except the temperate legumes had their largest leaf area in regime 2. Roots were less affected than tops.