Prior to this report, heat treatment (32.5°C, 24 h) was the method used to induce embryogenesis from Brassica napus microspores. Continuous culture at 25°C results in pollen development. This study ...shows that colchicine alone, at the non-inductive temperature of 25°C, can induce embryogenesis, thus demonstrating that heat shock is not required for embryogenic induction in B. napus cv. Topas. Embryogenic frequencies of over 15% were obtained by culturing isolated microspores with 25 μM colchicine for 42 h at 25°C. The microspore developmental stages responsive to colchicine were unicellular vacuolate and late unicellular, somewhat earlier stages than the population responsive to heat induction. Other groups have reported that heat-shock proteins are essential to the induction of embryogenesis. The present study offers a method of embryogenic induction without the use of heat which will allow discrimination between the factors associated with response to heat shock and those involved with changing cell development.
Effect of growth temperature on the fatty acid composition of triglycerides was compared for developing seeds and microspore-derived embryos of rapeseed. Plants were grown under standard conditions ...and subsequently seed development was allowed to take place at 15 or 25 °C. The composition of seed oil of the low erucic acid cultivar Aurora and a high erucic acid Gulle-derived line were not affected by growth temperature. The cultivar Reston showed a 30 % reduction in erucic acid level in seeds from plants grown at 25 °C as compared with seeds from plants grown at 15 °C. Seeds from plants that were transferred once during development from 15° to 25° or
vice versa, after two thirds of their development had been completed, showed an oil composition similar to seeds that developed completely at the initial temperature. Seeds transferred before or during the period of maximum lipid synthesis showed oil compositions that were similar to oil formed at the final temperature or intermediate between those of seeds completely grown at 15 °C or 25 °C, respectively.
In microspore-derived embryos (MDEs) similar responses to temperature in the level of erucic acid could be observed. However, absolute levels of erucic acid in MDEs of both Reston and Gulle were 30–50 % lower than in seed oil. Results are discussed in relation to possible regulatory mechanisms of temperature-induced changes in oil composition.
