Effects of Temperature on Growth and Physiology of Oncidium

Effects of environmental temperature on the contents of chlorophyll, soluble sugars, reducing sugars, starch and proline (Pro) of the cut flower variety Jinhui of Oncidium were studied. Four day/night temperatures, i.e., 12/4℃, 20/12℃, 28/20℃ and 36/28℃, were applied on the floral plants for a same period prior to the chemical analyses. The results showed that the chlorophyll content peaked at 28/20℃, followed by 36/28℃, and reached the lowest at 12/4℃. Soluble sugars decreased in the leaves as the temperatures rose; and, in the pseudobulbs maximized at 20/12℃, followed by 12/4℃, and minimized at 36/28℃.The leaves contained more reducing sugarsat 12/4℃ or 20/12℃ than at 28/20℃ or 36/28℃; whereas, the pseudobulbs had the highest content at 20/12℃, followed by 12/4℃, and the lowest at 36/28℃. For starch, the content was high at 12/4℃ and low at 36/28℃ in the leaves or the pseudobulbs; and, it was always higher in the leaves than in the pseudobulbs. Pro contents in the leaves and the pseudobulbs were the highe stunder 36/28℃, followed by 12/4℃, and the lowest under 20/12℃ or 28/20℃. The temperature exposure at 20/12℃appeared conducive to the growth of stems and leaves. However, it delayed the starting of the lateral buds. At 36/28℃, the budding was stimulated, but the growth and robustness of the budsseemed disadvantaged. And, at 28/20℃, both lateral bud germination and pseudobulb growth were enhanced.