Induced Changes in Reserve Materials in Evergreen Herbaceous Leaves

Seasonal Variations in the Physical and Chemical Properties of the Leaves of the Pitch Pine, With Especial Reference to Cold Resistance

“…This shows that the pressure exerted upon the leaf sample is operating against a force not present in August-the water-binding capacity of the colloidal gels, which have accumulated during the autumn months, and which have not been destroyed by the freezing treatment. By June 23, 1927, the 1926 leaves have reverted to the unhardened condition, and the pressure dehydration curve for this date parallels closely the curve for August 22,1926. The only important difference between the two curves is the larger decrease in the hydration of the tissues shown under the first increment of pressure on August 22, 1926, due to the larger water content .on that date.…”

“…Seasonal variations in the amount and chemical nature of food reserves in the cells of evergreen leaves are in themselves of physiological significance, and undoubtedly are important factors in determining changes in the osmotic pressures and other properties of the cells from one season to another. Although the investigations of Schultz (19), Lidforss (10), Miyake (13), Tuttle (22,23), and others have contributed important data to this subject, our actual information is still fragmentary, and a general re-working and extension of investigations in this field is desirable. The methods used should also be subjected to a critical scrutiny.…”

Composition and Growth Initiation of Dormant Bartlett Pear Shoots as Influenced by Temperature

“…WEBER (38) also reports an inverse relationship between starch and fat content in a number of species. TUTTLE (37), working chiefly with Linnaea, an evergreen species, claims that exposure to high temperature (200 C.) caused a conversion of oil into starch in the leaves, while a reconversion into oil was brought about by an exposure for eight days to 00 C. She states that in northwestern Canada, where chilling weather sets in early in the fall, the leaves of most evergreen trees are destarched by October and that they then contain large amounts of oils.…”