Control of Pecan Seedling Growth with a Heat Treatment to the Seeds

摘要

In previous experiments we were able to control the growth of pecan seedlings using synthetic growth retardants and naturally occurring phenolic compounds, but in this work we wanted to investigate if their growth could also be controlled by giving aheat treatment to the seeds. We subjected pecan seeds cv. Western to water soaking for 2 days, followed by a treatment at 2° and 30°C for 10 days in a humid substrate, using a refrigerator and a seed germination chamber, respectively. The control received only the water soaking. After this 10-day period, we found that the seeds receiving the 30°C treatment had sprouted, producing a root about 5 cm long, while the 2°C seeds showed no sign of germination. After this treatment, the seeds were planted in a bed under greenhouse conditions to record their emergence and shoot length. We found that the 30°C seeds emerged first, followed by the 2°C seeds and then the control. This response continued for some time until we had 95% emergence in the two treatments, including the control. Because of the initial differences in seedling emergence, the length of shoots was greater in the 30°C seeds, followed by the 2°C and then the control; however, after some time, we found that the shoot growth of the 30°Cseeds slowed and then stopped while the shoots of both the 2°C seeds and the control continued their normal growth, so that after a while the final shoot length of these seeds was higher than that of 30°C seeds. We present some speculations which possibly indicate that ABA and Jasmonic acid may be involved in the growth inhibition induced by the heat treatment given to the seeds