Phytochrome Control of Nyetinasty in Samanea as Modified by Oxgen, Submergence, and Chemicals

Samanea saman has rapid phytochrome-regulated nyctinasty: red light preceding darkness causes pinnules to close while far-rod light allows opening- Not only the initial angle of the pinnules, but the degree of control by phytochrome depends on the “subjective time of day” at which the tissue is exposed. Excised pairs of pinnules close rapidly when submerged in water; such closure is prevented by bubbling oxygen through the water. However, if submergence closure were due solely to low oxygen levels, then nonsubmerged pinnules in a pure nitrogen atmosphere should also close. Instead, they neither close nor respond to light, but they do respond when air is readmitted, indicating that oxygen is necessary for movement rather than for photoreception. The closure of submerged pinnules remains unexplained. Attempts to detect effects of red or far-red on oxygen uptake by pulvinus tissue were unsuccessful. The following method has been used to test the effects of various inhibitors and other substances: pinnules are excised at the first hour of the day, trimmed, submerged in a sealed chamber, given far-red light, and left in darkness while oxygen is bubbled through the medium. Concentrated test solutions are injected either initially or when the red and far-red exposures are given. Thus far, the substances tested have had little or no effect on the phytochrome response.     

Effect of certain inorganic chemicals on growth and spore germination of Alternaria tenuis auct., the fungus causing core rot of mandarin oranges in India

Summary Laboratory studies to determine the tolerance of an isolate ofAlternaria tenuis causing a black core rot of mandarin oranges (Citrus reticulata) have shown that presence of low amounts of manganese, zinc, iron, copper, boron, and molybdenum in a synthetic medium stimulated growth and sporulation of the fungus. Concentrations of 20 ppm or more of copper sulphate, boric acid, and ammonium molybdate, however, caused significant reduction of growth. Conidia of the fungus were very sensitive to even low amounts of copper, zinc, and iron. Copper sulphate was most toxic to spore germination followed, in order of inhibitory effect, by zinc sulphate, ferrous sulphate, and boric acid. Ammonium molybdate and manganese sulphate were stimulatory to spore germination at 5 ppm. There was a positive correlation between percentage of spore germination and average length of germ tubes in different concentrations of various chemicals. The possibility of using copper sulphate, zinc sulphate, and ferrous sulphate as spray materials for trees and as dip for ripe fruits to prevent black core rot are discussed.Assoc. Professor and Research Assistant, respectively. Publication under journal series No. 27 from Experiment Station, U.P. Agricultural University.