LEAF STRUCTURE AND PHOTOSYNTHETIC RATE OF SOME ORNAMENTAL SEEDLINGS

Abstract

Studies on leaf structure and photosynthetic rate of ornamental tree seedlings were carried out with 6 ornamental trees species found in Bangkok Metropolitan. The experimental seedlings were 12-18 month-old, including Pterocarpus macrocarpus, Mimusops elengi, Lagerstroemia speciosa, Cassia fistula, Tamarindus indica and Ficus altissiama. Leaf structure, stomatal number, stomatal size and distribution as well as diurnal and seasonal variations of photosynthetic rate and photosynthetic light response were determined. The results showed that leaf structure were different among species. Stomata of most species studied were hypostomatic type except Tamarindus indica which showed amphistomatic stomata. Stomatal frequency of Ficus altissiama showed the highest number, and Mimusops elengi showed the lowest. The biggest stomatal size was also found in Ficus altissiama, while Tamarindus indica showed the smallest size of stomata. Stomatal distributions were different among species. Study on photosynthetic rates of seedlings showed that diurnal patterns of net photosynthesis were similar in all species studied. Net photosynthesis measured in May were statistically higher than the rates measured in December for most species except Ficus altissiama and Mimusops elengi. Photosynthesis showed statistically response to light in all species studied. The light saturation points were between 350-650 /m²/s, and were higher in the momning than in the afternoon.