The Research On The Photosynthesis And Water Physiological Characteristics Of Three Species Of Osmanthus Trees

Osmanthus americanus and Osmanthus heterophyllus 'Goshiki' are both introuduced fromAmerica and Japan respectively, which belong to Osmanthus trees as well as Osmanthus fragrans.This paper mainly reasearch diurnal and seasonal changes in net Photosynthetierate(Pn) and therelationship between them and Physiological or ecological factors. Moreover, it explores theeffects on the photosynthetic by Internal factors of leaf. Last but not least, study on the waterphysio-ecological characteristics of three species of trees is to learn more about theacclimatization of the introduced species. It will provide theoretical references for widelycultivation and efficiently application of Osmanthus americanus and Osmanthus heterophyllus'Goshiki'. The principal results were as follows:(1) The three species of Osmanthus trees have obvious diurnal changes in photosyntheticrate. The curves of diurnal changes in photosynthetic rate show single-peaked at midday in springand autumn while it appeared double-peaked at midday in summer. It is earlier in spring than insummer and autumn when the peak value comes. In respect of photosynthetic rate during thegrowing season(spring,summer and autumn), the net photosynthetic rate from high to low areOsmanthus fragrans,Osmanthus americanus, Osmanthus heterophyllus 'Goshiki'.(2) Accroding to light compensationg points and light saturation points, Osmanthus fragransare both at a low level, so its shade endurance is strong. Due to the low light compensation pointsand high light saturation points of Osmanthus heterophyllus 'Goshiki', its Photopic Adaptation isweak. The capacity of three varieties light accommodation is: Osmanthus fragrans> Osmanthusamericanus> Osmanthus heterophyllus 'Goshiki'.(3) Physiological and ecological factors affect the photosynthesis of trees. Regress analysisindicates that the factors that influence net photosynthetic rate of three Osmanthus specieschanges among different season. The major effective factors are stomata conduction andtemperature in spring, light intensity and temperature in summer and CO2concentration in cellclearance, light intensity and stomata conduction in autumn. During the growing season(spring,summer and autumn), for Osmanthus americanus the most significant factor is CO2concentrationin cell clearance.(4) Average photosynthetic rate of the different leaf age is: Osmanthus fragrans> Osmanthusamericanus> Osmanthus heterophyllus 'Goshiki'.(5) The water physiology characteristic research on three species shows that Osmanthusfragrans' drought resistance is high while the other two species' is low.