Some Morphological and Biochemical Characteristics of C3 and C4 Plants Irradiated with UV-B

Four C₃ and two C₄ plants were subjected for 350 h to an enhanced UV-B radiation (280 to 310 nm) regime simulating a 0.18 atm. cm ozone level (solar angle 55°) in growth chamber. Different degrees of response among plant species were observed. UV-B radiation reduced plant height, fresh and dry weight, protein content, total chlorophyll, inhibited net CO₂ uptake and the Hill reaction activity. Some broad-leaved species with C₃ type of carbon assimilation were more susceptible to UV-B alterations of morphological and biochemical characteristics than the narrowleaved species with C₄ type photosynthesis.     

The Influence of Growth Regulators on Sprouting of Hydrilla Tubers and Turions

The effects of different growth regulators on the sproutingof hydrilla reproductive propagules (Hydrilla verticillata (L.F.)Rovle) were studied. Some growth regulators either had no effector inhibited sprouting. Ethephon, gibberellic acid, and thioureaincreased tuber sprouting significantly. Thiourea was less effectivein inducing sprouting in turions than in tubers. Maintainingtubers at 5 ± 2°C enhanced sprouting significantly.Tubers harvested in summer responded differently to growth regulatorsthan some of the tubers harvested in winter. Therefore, it wasconcluded that two types of dormancy exist in hydrilla tubers.