Hourly Variations in Carbohydrate Content of Leaves and Petioles

CARBOHYDRATE CHANGES WITHIN THE NEEDLES OF PINUS PONDEROSA AND PSEUDOTSUGA TAXIFOLIA

“…MEYER'S (7) It is, in general, to be noted that invert sugars undergo no periodic changes but necessitate the establishment of the nature and the rate of its metabolic rearrangements and disintegration as affected by the climatic conditions. CLEMENTS (2), working with the sunflower, and other investigators working with the apple and the maple, have reported actual migration of sucrose from the branches and petioles back into the leaves on the approach of cooler weather. This in itself would partially explain the relatively high constituent part of invert sugar in the October 20 sample, for both the pine and the fir.…”

“…MILLER'S (8) measurements show that the non-reducing sugars in the leaves of most plants are in excess of the reducinig sugars, and that the maximum point of increase of the total sugars is also the maximum point of increase of the non-reducing sugars. TOTTINGHAM et al (13) found that the time of day was less significant than temperature in determining carbohydrate composition; and that solar radiation is the limiting factor in the increases of nonreducing sugars when its value approaches 300 C. In addition to a comprehensive resume on this phase, CLEMENTS (2) contributed several important pieces of research. He found that starch in the leaf of the sunflower can drop from the maximum to the minimum within one to two hours.…”

SIGNIFICANCE OF PHLOEM EXUDATE OF CUCURBITA PEPO WITH REFERENCE TO TRANSLOCATION OF ORGANIC MATERIALS

“…More recently ENGARD (12) in a study of the carbohydrate translocation of the Cuthbert raspberry concluded that sucrose serves essentially as a translocatory form and that reducing sugars are also mobile. CLEMENTS (1) found reducing sugars more abundant than sucrose in the petioles of sunflower, soybean, and potato. Furthermore, sucrose was at times absent from the petioles when translocation was occurring.…”

“…The samples for tissue analysis consisted of: (1) the "upper petiole," the segment extending from 2 to 14 cm. below the blade; (2) the "lower petiole," extending from the petiole base to 6 cm.…”

“…Plants of Cucurbita pepo in the following physiological conditions were used in these studies: (1) young plants in a strongly vegetative condition, low in carbohydrates; (2) 5. Translocation is demonstrated in the minus-nitrate group by an accumulation of sugars in the petioles which were covered with black paper.…”