Effects of Phosphorus Deficiency on Growth and Metabolism of Sunflower

Publisher Website
Google Scholar
Abstract
The effects of P deficiency on sunflower plants (Helianthus annuus var. Mammoth Russian) were studied in sand culture. The first symptom noticed was the deeper green color of the leaves. Later the lower leaves became chlo-rotic, and chlorosis was followed by necrosis of the tissue. The plants were stunted, the stems hard and woody, and the roots much darker brown than those of the plus-P plants. The carbohydrates, reducing sugars, sucrose and starch, accumulated in the minus-P stems, especially in the early stages. This seemed to be due to a greater leaf development relative to the stems, rather than to any interference with protein synthesis as has been reported for other plants. P deficiency did not seem to interfere with the N metabolism of sunflower stems. The soluble N, fractions, nitrates, ammonia, amides, and amino acids did not accumulate, at least at the time of the 2d harvest. Others have reported an accumulation of these fractions in P-deficient plants. The plus-P stems were much higher in total P, soluble P, and insoluble P. In each set of plants these fractions were higher in the upper parts of the stems. More of the total P was present in the soluble form in the latter stems than in the former. P seemed to be readily translocated in the P-deficient sunflower stems.