Acetylene Reduction Activity and Non-Structural Carbohydrate Content of Hemarthria Altissima CV. Bigalta, After Defoliation

Abstract

Cut vs. uncut plants of Hemarthria altissima cv. Bigalta were studied to ascertain if the defoliated plants had significantly lower acetylene reduction activity (ARA) than unclipped plants. (Fig. a). Non-structural carbohydrate determinations were made of dried root samples. Roots sectioned with a freezing microtome were observed to contain starch in the cortical cells in the center of the root. ARA per gram of root, was significantly lower in the cut plants (p=. 02), and percent carbohydrate content was also significantly lower in the cut plants 17 days after clipping (p=. 001). A summary of percent carbohydrates found in the stems, crowns and roots of cut vs. uncut Hemarthria altissima is also shown. (Fig. b). Observations of root and shoot development indicated that cut plants had increased shoot growth, but initiated fewer new roots than the uncut plants. The ARA results are similar to, but at lower rates than reported with legume seedlings (Cralle, Heichel 1981) (Vance et al. 1979) and in field pastures (Halliday, Pate 1976).