A COMPARATIVE STUDY OF CONVENTIONAL, LEAFLESS AND SEMI-LEAFLESS PHENOTYPES OF PEAS: PHOTOSYNTHETIC CO2 FIXATION IN VITRO

Abstract

The effect of the "leafless" mutations (in which tendrils replace leaflets, af, and the stipules are reduced to a vestigial form, st) upon chlorophyll content, total protein, soluble protein, ribulose biphosphate carboxylase activity, and fresh weight/dry weight ratio were studied. Comparison of three near-isogenic lines of Century, Freezer and Trapper for the genotypes af af st st (leafless), af af + + (semi-leafless) and + + st st (reduced stipules) were compared with the conventional (+ + + +) plants. Chlorophyll contents were reduced by as much as 50% in the leafless phenotypes, as compared to the leafed plants. The leafless phenotype showed significantly higher levels of total nitrogen than the leafed plants. Tendrils had significantly lower levels of soluble protein than leaflets in two of the three cultivars examined. The fresh weight/dry weight ratio was significantly higher in the leafless phenotypes than the leafed types as a result of changes in morphology, going from a leaflet to a tendril. The internal arrangement of cells in the tendril was typical of pith and cortex tissue with very few intercellular spaces between the parenchyma cells. The intercellular space index within the tendrils was significantly lower than in the leaflet. In vitro measurements of ribulose biphosphate carboxylase activity were calculated per unit fresh weight and per unit chlorophyll. No significant differences were found between the different phenotypes per unit fresh weight; however, when the activity was measured per unit chlorophyll, the values for tendrils were significantly higher than for leaflets.