Influence of temperature during the preceding growth period of lucerne on its regrowth at different temperatures

One-year-old lucerne (Medicago sativa L. cv. 'Vernal') plants were grown to first flower through three cuttings in three temperature regimes, H (33°C day/24°C night), W (27718°C) and C (21712°C), to ascertain the influence of temperature preceding defoliation on subsequent growth. At first and second harvests, some pots were retained in the same temperature regime and the remainder were moved to the other regimes. The following temperature treatments were selected: H in the first, second and third cuttings (H-H-H), H-W-C, H-C-W, W-H-C, W-W-W, W-C-H, C-H-W, C-W-H and C-C-C. Foliage from all plants was harvested at first flower, but only six replications of each temperature treatment were harvested destructively at the end of each growth cycle. When plants were retained at the same temperature for the three cycles, the mass of plant parts and total non-structural carbohydrate (TNC) percentage in roots at each harvest increased with a decrease in temperature. Herbage yields were not influenced greatly by the temperature at which previous growth occurred, despite the large differences in root TNC. Cumulative herbage yields at the end of the third cutting were similar for all treatments having one H, W and C growth period, regardless of the order in which they occurred.