Levels In Leaf Research Articles

The Effects of Nitrate Supply and Grain Reserves on Fraction I Protein Level in the First Leaf of Barley

The timing and rate of nitrate application to barley seedlings grown under control and shade conditions can appreciably affect the maximum amount of Fraction I protein attained in the first leaf lamina. In unshaded seedlings early application results in a higher maximum amount of Fraction I protein per lamina, but not per unit lamina fresh weight. Late appli cation of nitrate however delays the age at which Fraction I protein reaches a maximum both in absolute terms and as a proportion of total soluble protein. For both control and shade-grown material early and higher rates of nitrate supply increase the maximum amount of soluble protein in the leaf but not the proportion represented by Fraction I protein. Lower rates of nitrate application have much less effect on first-leaf protein synthesis when application is given late. This is thought to be due to competition from the rapidly develop ing second leaf. Studies on the soluble protein content of shaded first-leaf laminae have shown that although grain size affects the maximum amount of Fraction I protein attained it does not alter the age at which this is attained; nor is the proportion of the total soluble protein accounted for by Fraction I protein affected by grain size or grain nitrogen content. A model is proposed to explain the contribution made by grain reserves and exogenous carbon and nitrogen supply to the development of the soluble protein content of the first leaf.

GROWTH AND DEVELOPMENT OF LITCHI CHINENSIS AS AFFECTED BY SOIL‐MOISTURE STRESS

The effects of soil‐moisture tension on growth and floral development of field‐grown Litchi chinensis, a woody subtropical fruit tree, were investigated. Floral initiation and fruit set were promoted by a high soil‐moisture tension for 6 months, beginning with June, 1967, or for 4 months, beginning with October, 1967. The normal floral‐initiation period in Hawaii is during the period November to January. The apical meristematic tissue, judged from the number of branches flowering, was apparently not adversely affected by a soil‐moisture stress, provided adequate water was available during the floral‐bud development period. Low soil‐moisture tension (0.3 bar) throughout the experimental period was inhibitory for floral bud initiation. High soil‐moisture tension inhibited growth of the trunk and the emergence of flush‐growths. Flowering was correlated significantly, and negatively, with growth. Leaf nitrogen and potassium levels were unaffected by water stress, but the phosphorus levels in leaf and stem were lowered by high‐moisture tension. Hydrolysis of starch under moisture stress, reported for some species, was not evident in the Litchi. No correlation between trophic constituents and flowering was observed.