Growth of Birdsfoot Trefoil and Alfalfa. IV. Carbohydrate Reserve Levels and Growth Analysis Under Two Temperature Regimes 1

‘Empire’ birdsfoot trefoil ( Lotus corniculatus L.) and ‘Vernal’ alfalfa ( Medicago sativa L.) were grown in two growth chambers set at 32/24 C (day/night) and 18/10 Net assimilation rate (NAR) was highest for both species in the cool regime, but NAR values of trefoil were only 63% and 52% of those of alfalfa in the cool and warm regime, respectively. Alfalfa in both temperature regimes and trefoil in the cool regime exhibited typical carbohydrate root reserve cycles. However, trefoil grown at warm temperatures did not restore its reserve. Alfalfa and birdsfoot trefoil flowered almost simultaneously in the cool regime (ca. 43 days). By comparison, the warm regime hastened flowering in alfalfa (24 days) and retarded it in trefoil (60 days). Delayed maturity of trefoil in the warm regime was attributed to a low NAR and to diseased roots and crowns which limited the energy supply. It was apparent that trefoil was not as adapted as alfalfa to warm temperatures.