Effect of soil moisture stress on absorption & translocation of phosphorus applied to leaves of sunflower

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Abstract
Leaves of a dwarf form of the sunflower plant were treated with p32-labelled NaH2PO4 at various levels of soil moisture stress. After 24 hours, plants at 0.3 atmosphere had absorbed 80% of the applied P as compared with an absorption of 33% at 5 atmospheres and 15% at 16 atmospheres. In plants at 0.3 atmosphere 16% of the absorbed P was translocated from the leaf in 24 hours as compared with less than 7% in plants at 5 and 16 atmospheres. Moisture stress altered the distribution of the translocated P within the plant. Plants with adequate moisture accumulated a higher concentration of P in growing regions than did plants exposed to moisture stress. Permeability of the leaf surface and effectiveness of phloem transport were reduced as availability of water to the plant was decreased by soil moisture stress.