Time to flowering is an essential component of chickpea (Cicer arietinum L.) adaptation in the short growing season of western Canda. The initiation of flowering and mechanism of the photoperiod response in chickpeas are not sufficiently understood. The timing and duration of the photoperiod-sensitive phase in respect to floral initiation and flower development phases is less understood. The objectives of the study were: 1) to evaluate if a photoperiod sensitive phase exists in chickpea and 2) to examine the flowering responses of the selected chickpea genotypes grown in a range of thermal regimes combined with either long or short days.

Eight chickpea genotypes were evaluated to determine the photoperiod sensitive phases. The genotypes were grown in seven replicates in separate growth chambers adjusted to LD (16/8 h) and SD (10/14 h) with temperature at 22/16 ⁰C in both chambers.  Individual plants of each genotype were transferred in a time series from LD to SD and vice versa. The control plants were grown continuously under the respective photoperiods. There was no significant difference in days to flowering under LD and SD and subsequent transfers for the day neutral genotypes. For the rest of the genotypes, the day length sensitive phase was identified. This phase extends beyond flower initiation and the duration is genotypes specific.

  Evaluation of selected genotypes under two photoperiods (10 hours and16 hours) and three diurnal temperature regimes (16/8⁰C, 20/12⁰C and 24/16⁰C; day/night) demonstrated that temperature profile had more profound effect than photoperiod on flower induction and crop duration in chickpea. For the photoperiod sensitive genotypes, changing the diurnal temperature from 24/16⁰C (day/night) to 16/8⁰C (day/night) delayed flowering by an average of 50 days compared to 30 days delayed in flowering from changing  from LD to SD.  The photo-thermal response of the genotypes was a linear function of temperature.