Premium
Studies on the distribution, re‐translocation and homeostasis of inorganic phosphate in barley leaves
Author(s) -
MIMURA T.,
SAKANO K.,
SHIMMEN T.
Publication year - 1996
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1996.tb00253.x
Subject(s) - apoplast , chromosomal translocation , vacuole , homeostasis , phosphate , biology , plant growth , botany , cytoplasm , horticulture , biochemistry , cell wall , microbiology and biotechnology , gene
Changes in inorganic phosphate (P i ) concentrations in barley leaves during growth of plants with sufficient or deficient supplies of P i were studied. Measurements of the P i distribution from subcellular levels to the leaf tissue level under the same experimental conditions allowed us to analyse the relationship between the P i homeostasis of various compartments and P i re‐translocation in the whole plant. Under P i deficiency, the finding of growth‐dependent changes in the P i concentrations of whole leaves established that P i was re‐translocated from the older leaves to the young leaves. Translocation of 32 P i was also confirmed with an ‘imaging plate’ system, which made it possible to follow P i movement in the same plantlet. To analyse the mechanism of P i re‐translocation, the P i distribution amongst various compartments of the leaves was measured. Under P i deficiency, the cytoplasmic P i concentration of the first leaf remained constant until 16d after sowing, while vacuolar P i was completely exhausted after 8 to 10d. Exhaustion of vacuolar P i in the first leaf coincided with the appearance of the second leaf. The P i concentration in the apoplast changed similarly to that of the whole leaf. However, the apoplastic P i concentration was affected to some extent by the vacuolar P i concentration and the growth of the younger leaf, because the main change in apoplastic P i concentration coincided with the time of the disappearance of the vacuolar P i and the appearance of the younger leaf. The P i concentration in the apoplast was about 0.1 to I molm −3 , even in the absence of P i , which was much higher than that in the usual soil environment (a few mmolin −3 ). This suggests that the P i absorbed by root cells is concentrated in the transport process from the root to the leaf apoplast. The content of P i in the xylem exudate was constant irrespective of growth culture conditions. The root may be functioning as the constant P i supplier to the above tissues.