Temperature and Mechanical Stimuli to Regulate Pear and Papaya Growth(Plant Growth Regulation by Physical and Mechanical Stimuli, For Further Development of Horticulture in East Asia)

Abstract

Tree size and harvest season might be designed and controlled in growth chambers or by elevation in the field. By means of higher temperature, thousands of hectors of Japanese pears in Taiwan are being cultivated to produce off-season fruit year around, mainly from spring through fall months. The height of a Japanese pear tree with setting fruit might be 30 cm if the tree is kept in 15 : 25 : with full light intensity through out the year until the flower buds are initiated and begin to develop. Like banana trees, papayas are susceptible to wind damage. Papaya is also susceptible to the papaya ring spot virus (RSV) prevalent in Taiwan and other tropical and subtropical areas. Nethouses were constructed to prevent aphids from transferring the virus. In the nethouse, decreased light intensity induced vigorous vegetative growth of the papaya. When the tips of the papaya touched the net, the canopy could not spread, forcing farmers to remove the net. The papaya soon became infected by RSV resulting in higher cultivation costs. In order to increase the life span of papaya in nethouses, a mechanical stimulus was applied to the papaya by cleaving and bending the trunk to various heights. This technique facilitated evaluation of wind damage, disease susceptibility, and duration of the harvest. Research shows papaya trunks can be trained to a tunnel-type growth form extending the duration of the harvest for an additional year or more. This suggests that the plastic recovery property of the papaya trunk allows cultivation economically in greenhouses or nethouses, and eventually in the field with greatly reduced affects from wind damage.