Effects of Temperature and Photoperiod on Flowering in Lentils (Lens culinaris Medic.)

Factorial combinations of three photoperiods (10, 13 and 16 h), two day temperatures (18 and 28 °C) and two night temperatures (5 and 13 °C) were imposed on nodulated plants of six diverse genotypes (cultivars and land-races) of lentil (Lens culinaris Medic.) grown in pots in growth cabinets from vernalized (1.5 ±0.5 °C for 30d) or non-vernalized seeds (i.e. 144 ‘treatment’ combinations). The times from sowing to the appearance of first open flowers were recorded. Vernalization, long days and warm temperatures hastened flowering but genotypes differed in relative sensitivity to each of these factors and in time to flowering in the same most-inductive environment. Rates of progress towards flowering (i.e. 1/f the reciprocals of the times to first flower, f) in all genotypes, vernalized or not, were linear functions of both mean temperature, $t¯$, and photoperiod, p, with no interaction between the two terms. So, over a wide range of conditions (covering the photo-thermal regimes experienced by lentil crops world-wide), time to flowering can be described by the equation: 1/f= a + b$t¯$+cp, where a, b and c are constants which differ between genotypes and the values of which provide a sound basis for screening germplasm for sensitivity to temperature and photoperiod. Although these two environmental factors affect the same phenological event (i.e. time to flowering) our data suggest the responses are under separate genetic control. Seed vernalization consistently increased the values of both a and b in all genotypes. The implications of these collective findings for the screening of lentil germplasm are discussed.