Abstract
This study was carried out to examine the effect of ethylene, which is evolved from organic materials applied to soil, on the growth of citrus trees.
The roots were exposed to 0, 0.05, 0.5, 5, and 50ppm ethylene in the soil atmosphere for 4 weeks. Shoot elongation, total and root fresh weights, main root length, and succinate dehydrogenase activity of roots, were severely inhibited at and above 5ppm ethylene. Ethylene application also caused swelling of root tips and brownish coloration of roots. At 0 and 0.05ppm ethylene most root hairs were observed in patches in the zone 5-15mm behind the tip, and they were conical, papillate, and pear-shaped. With increasing ethylene concentration, however, the number of tubular-shaped root hairs increased. At 50ppm, most of the root hairs were withered or lost. Ethylene application also affected the contents of N, P, K, Ca and Mg in leaves, shoots, and roots. In soil where unfermented organic materials have been applied, ethylene has often been detected at concentrations high enough to inhibit growth.
