Impact of High Temperature and Drought Stress on Physiology and Re-Growth of Winter Canola.

Regrowth in canola has been observed in several canola growing regions across the United States, particularly in dry years. High temperature and drought stress during flowering can induce regrowth due to its impact on reproductive processes and seed-set. The objective of this research is to determine if regrowth can be induced during the recovery period after exposing canola to short periods of high temperature and/or drought conditions in controlled environments. Four canola cultivars (Casino, Wichita, KS 2185 and KS 3254) were grown at optimum temperature (20/13ºC) under fully irrigated conditions until floral bud initiation. Starting at bud initiation, each cultivar was exposed to four treatments: (a) optimum temperature (OT, 20/13ºC) and fully irrigated; (b) high temperature (HT, 30/23ºC) and fully irrigated; (c) OT, and drought; and (d) HT and drought for 14 days. Following each stress, all plants were exposed to OT and were fully irrigated and allowed to recover. Data on chlorophyll fluorescence (thylakoid membrane damage) and leaf chlorophyll during stress periods, pollen viability and seed-set at flowering, and number of new branches and leaves during recovery were measured. Stress caused damage to thylakoid membranes and decreased leaf chlorophyll content, pollen viability, and seed-set across all cultivars. There were no cultivar differences in response to stress. Plants recovered from exposure to HT and/or drought conditions by putting on new growth, which occurred about 15 days after the stress was relieved. Cultivars varied in time taken to initiate and produce regrowth during recovery stages. Initiation was earlier (about 5 days) and faster in cultivars Casino and Wichita when compared to cultivar KS 2185. This preliminary research suggests that measuring recovery from stress in terms of timing and amount of regrowth can be a measure of a cultivar’s regrowth potential.