Environmental control of growth, flowering and yield of lentil and chickpea in Saskatchewan
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Yield of a crop depends on growth and developmental responses to various environmental factors. Agronomic practices for high yield of two new crops of Saskatchewan, lentil (Lens culinaris Medik.) and chickpea (Cicer arietinum L.), must be based on these responses to variations of the local climate. Controlled environment and field studies were conducted: 1) to determine the effects of variations in temperature, soil moisture and radiation intensity on physiological characteristics and growth of Laird lentil and Cheston chickpea; 2) to determine the effects of temperature and photoperiod on time to first flower in five genotypes of lentil; and 3) to compare the efficiency of the degree-day, rate-factor and equivalent hours of maximum net photosynthesis (EHMNP) models for predicting time of first flower in the same five lentil genotypes. The optimum temperature for net photosynthetic rate (Pn) of both lentil and chickpea was around 18°C. The decline of Pn at high temperatures was accompanied by increases in respiration (R) and transpiration (E1 rates. Rates of all these physiological processes decreased as temperatures dropped below the optimum temperature. Exposure to a single hot day (35°C) decreased Pn of lentil for 6 to 78 h, but did not decrease Pn of chickpea, whereas exposure to a single cold night (0°C) decreased Pn of chickpea for 6 to 54 h and Pn of lentil for 30 h, depending on growth stage. Both exposures increased R only at a later growth stage of both species for at least 78 h. A soil moisture deficit decreased Pn, E1 , stomatal conductance (gs) and shoot water potential and accentuated leaf senescence of both species. Chickpea produced higher seed yield than lentil only at the lowest soil moisture supply, but both responded to irrigation. Radiation intensity did not affect gs, probably due to the short interval between changes in radiation intensity. Low temperature or short photoperiod increased time to flower in all five genotypes of lentil in the controlled environments. However, in the field flowering responses were related to variation in temperature only. All developmental models adequately predicted time of first flower of five lentil genotypes within each of six field environments. However, only degree-days and the two variations of the rate-factor adequately predicted the time of first flower over a wide range of environments. The rate-factor model based on mean daily temperature and photoperiod was most successful, but must be validated for each crop and each environment.