METHODS FOR IMPROVING COLD OR FREEZING TOLERANCE, REDUCING THE GROWTH RATE, OR INHIBITING THE GROWTH OF PLANTS, AND FOR IMPROVING THE GERMINATION RATE OF PLANT SEEDS

摘要

The accumulation of the osmolyte glycine-betaine is associated with increasedfreezing tolerance (FT) in wheat. An exogenous application of betaine at roomtemperature increased their FT by more than 5°C. The treated plants showed someof the characteristics of cold-acclimated plants and expressed the low temperatureresponsive gene Wcor410 encoding a major membrane associated protein. Thecombined exposure to low temperature and betaine resulted in a cumulative effect onthe improvement of FT surpassing the genetic potential of the plant to withstandfreezing. This important finding indicates that an exogenous application of betainebefore a predicted frost may be exploited to substantially improve cold or freezingtolerance in sensitive plants. Also disclosed is a method of reducing the growth rateof a plant by at least 30%, which comprises the step of treating the plant with aneffective dosage regimen of betaine or derivative thereof which is not lethal, preferablynon-toxic to the plant. When growing the spring wheat variety Glenlea, in the presenceof 500 mM of glycine betaine for four days, the growth rate thereof was reduced byabout 75%. Another aspect of the present invention is a method of inhibiting the growthof a plant, which comprises the step of treating said plant with a high dose regimen orbetaine or derivative thereof. At lethal doses, this method results in killing undesirableplants. Another aspect of the present invention is a method of improving thegermination rate of plant seeds at a temperature which is higher than about 0°C butnot lower than the coldest temperature that the plant seeds can withstand, whichcomprises the steps of administering to the seeds an effective dosage regimen ofbetaine or derivative thereof, and allowing the same to germinate at cold temperatures.