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Phosphorus export from roots to shoots of barley, buckwheat and rape seedlings with different P status
Author(s) -
Schjørring Jan K.,
Jensén Paul
Publication year - 1987
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.1399-3054.1987.tb08696.x
Subject(s) - shoot , phosphorus , hordeum vulgare , brassica , polygonaceae , biology , nutrient , horticulture , botany , chemistry , poaceae , organic chemistry , ecology
Seedlings of barley ( Hordeum vulgare L. cvs Salka and Zita), buckwheat ( Fagopyrum esculentum Moench) and rape ( Brassica napus L. ssp. napus cv. Line) were grown in complete nutrient solutions with 8 or 10 different P concentrations in the range of 0–2 m M . Phosphate export from roots to shoots was determined from the amount of 32 P (or 33 P) absorbed and exported to shoots in 1 h from a nutrient solution containing 0.1 m M radiolabelled phosphate. P export was also determined in the presence of a metabolic uncoupler (DNP, 2.4‐dinitrophenol) and a protein synthesis inhibitor (CH, cycloheximide). Phosphorus export from roots to shoots reached a maximum at a certain optimum level of phosphorus in shoots and roots, and decreased at both higher and lower P levels. Maxinmm P export was 1.7 ± 0.2 and 4.5 ± 0.5 (mean ± se of the three species) times higher than the P export at the lowest and highest [P] root , respectively. Hill plots as well as plots of the untransformed decreasing P export vs root or shoot P concentrations above the optimum were linear and had high correlation coefficients. The Hill coefficient (n H ) based on [P] root , was —7.7 for barley cv. Salka and varied between ‐3.8 and ‐4.5 for the other species. Based on [P] shoot ot n H was—16.1 for barley cv. Salka, ‐3.7 for barley cv. Zita and ‐6.4 for the two dicotyledonous species. Relative to the amount of P simultaneously absorbed by the root system, the import of P per unit shoot weight decreased linearly over the whole range of shoot P concentrations in the dicotyledonous species. In contrast, the relative import of P per unit shoot weight of the two barley cultivars increased at low levels of [P] shoot and decreased at higher levels. DNP and CH almost eliminated P export from roots to shoots of seedlings with low or high P status. In seedlings with medium P status only 60 to 75% of the P export was affected.