Carbohydrate Metabolism in theNarcissusLeaf

Abstract

Carbohydrate contents of both the photosynthetic and the storage organs of Narcissus tazetta L. were determined at four stages in their development under both ‘natural’ growing conditions and under conditions of varying light intensities. Starch was abundantly stored in all the storage organs, particularly in the bases of the photosynthetic organs under high light intensity and also at the second dormant stage. However, its level remained relatively stable in the green part of the foliage leaf and the scape at different stages and appeared not to be affected by light except at very high intensity. It was found in both the bundle sheaths and guard cells. Sucrose, which is the first sugar of photosynthesis, was continuously exported from the green parts of the blade and the scape to their bases where it was also stored. In the dark the sucrose level became low in the green blade and the green scape but it rose with increase of light intensity. The hexose level was very low at the dormant stage in all organs examined but rose as they matured and exceeded that of sucrose in the green organs except in high light intensity. Hexose is formed presumably as a result of sucrose hydrolysis and is constantly lost, presumably through respiration. At senescence sugar disappeared almost completely from all the organs, while nearly 10 per cent of residual dry weight of starch remained in the dead tissues. The interrelationship between the carbohydrates and their movement in the leaf is discussed.