INFLUENCE OF LIGHT INTENSITY ON GROWTH, NODULATION AND NITROGEN FIXATION OF SELECTED WOODY ACTINORHIZAL SPECIES
Abstract
Container-grown Alnus glutinosa (L.) Gaertn., Myrica pensylvanica Lois., Elaeagnus umbellata Thunb. and Elaeagnus angustifolia L. were grown at 20, 37, 53, 70 or 100% of natural light to determine the influence of light intensity on growth, nodulation and nitrogen fixation. Optimum growth of Alnus glutinosa occurred in full-sun-grown plants. Acetylene reduction rates also were maximum in full sun and were highly correlated with chlorophyll content per unit leaf area, specific leaf weight and nodule starch content. Number and fresh weight of nodules as well as total N content in the plants was higher in full-sun-grown plants than in other light intensities. Optimum growth of Myrica pensylvanica occurred in plants grown under 70% light intensity. Plants in this treatment had more chlorophyll per unit leaf area, but less leaves than plants grown in full sun. Acetylene reduction rates were maximum at 70% light, but reducing and non-reducing sugars in the nodules increased with increased light intensity. Number of nodules followed the same pattern as sugars. However, fresh weight of nodules was not affected by light. For Elaeagnus umbellata, optimum shoot/root ratio occurred in plants grown under 70% light. Acetylene reduction rates were maximum in full sun, these rates were correlated with non-reducing sugars content in the nodules. However, greater total activity was obtained at 70% light, because of greater nodulation. Plants grown under light also had higher N content than plants grown in other treatments. Optimum growth of Elaeagnus angustifolia occurred towards high light intensities. Maximum rates of acetylene reduction and highest N content were obtained under full sun. However, number and fresh weight of nodules were not affected by light intensity. Results of these studies indicated that light intensity affected both growth and nitrogen fixation rates of actinorhizal species. However, there is an optimum intensity of which growth and nitrogen fixation are maximized which appears to be species-dependent with respect to light intensity. Supply of photsynthates through the light intensity appeared to be a factor in regulating nitrogen fixation rates, which in turn affected the growth in most of the species studied.
Degree
Ph.D.
Subject Area
Botany
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.