THE EFFECTS OF SOIL-MOISTURE AND SHADING TREATMENT ON BOUGAINVILLEA BRACT

Environmental factors exert great influence on the blooming of Bougainvillea. This study focuses on the relation between meteorological factors, such as insolation, and soil moisture and the growth, the development of thorn-inflorescence axis, and the bract formation of Bougainvillea. This study is to better understand the promotive and inhibitory environmental conditions concerning the blooming of Bougainvillea. The results are summarized as follows: Shading treatment decreases the amount of insolation, the insolation received by plants in shading and non-shading area is 36% (i.e., sunshine penetrating into the greenhouse) and 67% of that received by plants in open area respectively. During the study period, the average daily temperature is 23.6-degrees-C and 23.7-degrees-C in shading and non-shading areas, respectively. The difference in temperature is not significant. With short duration of insolation (5 hrs) and temperature of 23-28-degrees-C, shading treatment induces the shooting of branch and decreasing of blooming. The average number of blooms of each plant in shading area is 649.7, 189.9 less than those in non-shading area. The difference in number of blooms is significant. With monthly average temperature below 20-degrees-C and the lowest temperature at 10-degrees-C during the blooming season, the number of bloom decreases dramatically, 351.9 and 553.5 of blooms for plants in shading and non-shading areas, respectively. The difference is not significant with variance analysis. The results indicate that insolation has greater effect on the blooming of Bougainvillea when the temperature is higher than 20-degrees-C. Also, the color of Bougainvillea bract is lighter in plants in shading area than those in non-shading area. The size of the bract is larger in plants in shading area than that in non-shading area, with 0.1 cm larger in length and width. Various soil moisture contents (90, 60, and 30%) showed significantly different effects on the growth, and the bract formation of Bougainvillea. The higher the soil moisture, the longer the length of the branch and the length between nodes, and the larger the number of nodes and the lowest node with inflorescence (opposite effect observed during low temperature period). The difference in the number of blooms resulted from different soil moisture contents is significant. During high temperature period, the average number of bloom is 807.7, 811.0, and 615.7 respectively for plants with 90, 60, and 30% soil moisture content. During low temperature period, the average number of bloom is 748.7, 422.3, and 187.0 respectively for plants with 90, 60, and 30% soil moisture content. The results indicate that high soil moisture promotes, especially during low temperature period, the bract formation. Soil moisture of 30%, with or without shading, is shown to be inadequate to support the growth of Bougainvillea.