A PRELIMINARY STUDY ON THE EFFECT OF VESICULARARBUSCULAR MYCORRHIZAL FUNGUS ON CALCIUM UPTAKE OF CITRUS SEEDLINGS
TANG ZHEN-YAO LAI-YI (Citrus Research Institute of Chinese Academy of Agricultural Science, Chongqing) HE SHOU-LIN (Agricultural University of South-west, Chongqing)
Two pot cultivation experiments were carried out by means of radio isotopic ~(45)Ca for determining the ability of calcium absorption in citrus seedling influenced by vesicular-arbuscular (V-A) mycorrhizal fungus. A Hoagland's culture solution containing radioactive ~(45)Ca (NO_3)_2 with equal microcuries was added to each plant. Seedlings of two citrus species, Trifoliata orange [Poncirus trifoliata(L.) Raf.] and Goutou orange, a variety of Sour orange (Citrus aurantium L.) were grown in sterilized red soil and soil free media and treated with different process respectively: (1) inoculated with V-A mycorrhizal fungus (Glomus citricolum), (2) nonmycorhizal contrast. Results from experiment I showed that mycorrhizal infection of Trifoliata seedling reached 24.5％, five months after inoculation. Total calcium content, radioactivity and ~(45)Ca amount absorbed from fertilizer in upper part of mycorrhizal plant increased about 75％ more than those of nonmycorrhizal one. The result indcated that calcium was significantly absorbed and transported into upper part of plant by mycorrhizal fungus. The results of another experiment showed that the infection percentage of trifoliata seedlings in soil free was higher than that in red soil. The mycorrhizal infection of Goutou orange was 49.5％ and 30.1％ vesicles were formed three months after inoculation. Autoradiograms directly indicated that mycorrhizal fungus enhanced the cability of ~(45)Ca absorbtion and transported calcium into upper part of the plant. The content of total calcium was significantly higher in mycorrhizal plants.