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Diurnal variation in “bound” and “free” water and other factors in the sap expressed from the leaves of Phalaris tuberosa

Research paper by J. Calvert

Indexed on: 01 Sep '35Published on: 01 Sep '35Published in: Protoplasma



Abstract

The total water and the free water in 100 gms. of the sap expressed from the leaves are significantly higher in the morning (when transpiration is relatively low) than in the afternoon (when transpiration is relatively high).The behaviour of the bound water in 100 gms. of the expressed sap is the reverse of the free water, being significantly higher in the afternoon than in the morning. This is due to the greater relative decrease in the free water in the afternoon than occurred in the total water.The total water per gram of dry matter, the free water per gram of dry matter and the bound water per gram of dry matter, in the expressed sap were all significantly greater in the morning than in the afternoon.The decrease in the free water per unit of dry matter between morning and afternoon was considerably greater than the decrease in the bound water per unit of dry matter with the result that while the free water exceeded the bound water in the morning the bound water exceeded the free water in the afternoon.The leaves had a significantly higher water content in the morning than in the afternoon.The loss of water from the leaves during the day induced a greater density in the sap expressed from the leaves.The quantity of sap and the quantity of water expressed from the leaves varied with the water content of the leaves.The water per gram of dry matter remaining in the tissue after 3000 lbs. per sq. inch pressure was the same for the leaves collected in the morning as for those collected in the afternoon.The variations in the factors dealt with in the present paper in their relation to the water deficit in the plant were parallel to the results found in a study of the seasonal trends.