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Mechanism of phosphorus‐induced zinc deficiency in cotton. II. Evidence for impaired shoot control of phosphorus uptake and translocation under zinc deficiency
Author(s) -
Marschner Horst,
Cakmak Ismail
Publication year - 1986
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1986.tb03387.x
Subject(s) - chromosomal translocation , nutrient , shoot , phosphorus , zinc , phosphorus deficiency , zinc deficiency (plant disorder) , chemistry , plant physiology , botany , agronomy , horticulture , biology , biochemistry , organic chemistry , gene
Cotton ( Gossypium hirsutum L. cv. Deltapine 15/21) plants were precultured for 19 to 25 days under controlled climatic conditions in nutrient solutions with different levels of Zn. With the onset of visual Zn‐deficiency symptoms the pH of the nutrient solution decreased from 6.0 to about 5.0. In contrast, Zn‐sufficient plants raised the pH of the nutrient solution to about 7.0. In short‐term studies it could be demonstrated that the Zn nutritional status of the plants remarkably influenced the uptake and translocation rates of mineral nutrients. Compared to Zn‐sufficient plants, P uptake rate in severely Zn‐deficient plants was increased by a factor of 2 to 3, whereas the uptake rates of K, Ca and particularly NO 3 decreased. The accumulation of P in the roots of Zn‐deficient plants was either not affected or even lower than in Zn‐sufficient plants. Thus, Zn deficiency had a specific enhancement effect on root to shoot transport of P. This enhancement effect of Zn deficiency on uptake and transport of P was similar at nutrient solution pH values of 7.0 and 5.8; i.e. it was not the result of acidification of the nutrient solution. After application of 36 CI, 86 Rb and 32 P to plant stems, basipetal transport of 36 CI and 86 Rb was not affected by the Zn nutritional status of the plants. However, in Zn‐deficient plants, only 7.8% of the 32 P was translocated basipetally compared to 34% in the Zn‐sufficient plants. A resupply of Zn for 19 h to Zn‐deficient plants enhanced basipetal 32 P transport. The results indicate that a feedback mechanism in the shoots is impaired in Zn‐deficient plants which controls the P uptake by roots and especially the P transport from roots to shoots. As a result of this impairment toxic concentrations of P accumulate in the leaves. The mechanism responsible is likely the retranslocation of P in the phloem from shoots to roots.