Polysaccharide Composition of Leaves
PLUM leaves (Prunus domestica) contain sufficient amounts of starch, cellulose, hemicellulose, and pectic substances to recommend them for studies of the biosynthesis and possible inter-relationships of these leaf polysaccharides and their monosaccharide precursors1. Experiments involving photosynthesis by plum leaves in carbon dioxide labelled with carbon-14 and subsequent fractionation of the leaf polysaccharides revealed marked differences, both in the extent to which carbon-14 was incorporated into the different monosaccharides of each fraction, and also in the specific activities of each monosaccharide from different fractions2,3. Further investigations could be facilitated by using leaves relatively richer than plum leaves in any one polysaccharide constituent. There is little information on this point, consequently a diversity of leaves has been examined for polysaccharides (Table 1).
Influence of temperature and growth stage on the diurnal fluctuation in the non‐structural carbohydrate content of kikuyu (Pennisetum clandestinum Hochst)
The non‐structural carbohydrates of kikuyu (Pennisetum clandestinum Hochst) seem to consist mainly of sucrose. Total non‐structural carbohydrate content increased rapidly during the morning and reached maximum concentration in the afternoon. After sunset, the concentration decreased rapidly, reaching a minimum level by midnight. Low temperatures resulted in a significantly higher non‐structural carbohydrate content in all plant fractions than at warmer growth temperatures. Non‐structural carbohydrate concentrations were higher in stem tissue than in leaf material and the values were higher in 3‐week than in 6‐week regrowth.
THE BIOSYNTHESIS OF C13 COMPOUNDS : I. THE BIOSYNTHESIS OF C13-LABELED STARCH
1. Starch, containing 7.05 atom per cent C13 excess has been produced in the mesophyll cells of bean leaves, starting with C13O2 containing 7.26 atom per cent C13 excess. Approximately 67 per cent of the C13 taken up by the leaves was determined in the starch fraction. 2. The soluble carbohydrate, containing 6.72 atom per cent C13 excess, accounts for approximately 23 per cent of the C13 taken up by the leaves. The remainder was principally in the coarse tissue fragments fraction (9.73 per cent of the C13 utilized). 3. The apparatus and procedures used in this experiment are described.