Effect of temperature on number of thorns and its relationship to plant characters of bird pear (Pyrus sp.)

The experiment is conducted to study the effect of temperature on the number of thorns and the relationship between thorns and other characters of 'Bird' pear (Pyrus sp.) The open pollinated seedlings of 'Bird' pear from Chuo-Lan and Da-Hu area of Taiwan are planted in 15cm pots, and treated with 30/25degreesC, 25/20degreesC, 20/15degreesC, 15/13degreesC (day /night degreesC), together with a control group that are treated under field conditions. The results show that the number of thorns increases as the temperature decreases. The control plants have the number of thorns of plants grown between 20/15degreesC and 25/20degreesC. For Chuo-lan, the number of thorns is significantly higher under the temperatures of 15/13degreesC, and 20/15degreesC than under the other three conditions. For Da-hu, the thorns are significantly higher under the temperature of 15/13degreesC and 20/15degreesC, as compared to plants grown under natural conditions, 25/20degreesC and 30/25degreesC. There was a significant difference of plant characters among the five different conditions under which these plants were grown. This shows that the cooler the temperature, the more advantageous it is to the growth of the thorns of 'Bird' pears. A regressive analysis of thorns and plant characters show that there is a good correlation between them in most of the temperature conditions, especially the plant height. The correlation between thorn and plant height were significant in most treatments, especially in the treatment which induced thorny plants. It can be concluded that temperature has a great influence on the growth of thorns of spurs of the 'Bird' pears, especially grown under cooler temperature. In cool conditions the number of thorns per plant show good correlation to plant height. This result in thorns will provide a good selection index of 'Bird' pear for plant height.