Abstract
ABSTRACT 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.
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Claims 11
Claim · model-written summary
Under Pi deficiency, growth-dependent changes in Pi concentrations of whole barley leaves established that Pi was re-translocated from older to young leaves.
- Taxon
- barley
.jpg?width=60)
Hordeum vulgaret0 - Treatment
- P i deficiencye0
- Outcome
- P i was re‐translocated from the older leaves to the young leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
t0“barley leaves”
e0“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”
Claim · model-written summary
Translocation of 32Pi in barley plantlets was confirmed with an imaging plate system.
- Taxon
- barleyHordeum vulgaret0
- Outcome
- Translocation of 32 P ie1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“barley leaves”
e1“Translocation of 32 P i was also confirmed”
Claim · model-written summary
Under Pi deficiency, the cytoplasmic Pi concentration of the first leaf remained constant until 16 d after sowing.
- Taxon
- barleyHordeum vulgaret0
- Organ / stage
- first leafe2
- Treatment
- P i deficiencye2
- Outcome
- cytoplasmic P i concentratione2
- Direction
- remained constante2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“barley leaves”
e2“Under P i deficiency, the cytoplasmic P i concentration of the first leaf remained constant until 16d after sowing”
Claim · model-written summary
Vacuolar Pi was completely exhausted after 8 to 10 d of Pi deficiency.
- Taxon
- barleyHordeum vulgaret0
- Outcome
- vacuolar P ie3
- Direction
- exhaustede3
- Value
- 8 to 10de3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“barley leaves”
e3“vacuolar P i was completely exhausted after 8 to 10d”
Claim · model-written summary
Exhaustion of vacuolar Pi in the first leaf coincided with the appearance of the second leaf.
- Taxon
- barleyHordeum vulgaret0
- Organ / stage
- second leafe4
- Outcome
- Exhaustion of vacuolar P ie4
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“barley leaves”
e4“Exhaustion of vacuolar P i in the first leaf coincided with the appearance of the second leaf”
Claim · model-written summary
The Pi concentration in the apoplast changed similarly to that of the whole leaf.
- Taxon
- barleyHordeum vulgaret0
- Organ / stage
- apoplaste5
- Outcome
- P i concentration in the apoplaste5
- Direction
- changed similarlye5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“barley leaves”
e5“The P i concentration in the apoplast changed similarly to that of the whole leaf”
Claim · model-written summary
Apoplastic Pi concentration was affected to some extent by the vacuolar Pi concentration and the growth of the younger leaf.
- Taxon
- barleyHordeum vulgaret0
- Organ / stage
- younger leafe6
- Compound
- vacuolar P i concentratione6
- Outcome
- apoplastic P i concentratione6
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“barley leaves”
e6“the apoplastic P i concentration was affected to some extent by the vacuolar P i concentration and the growth of the younger leaf”
Claim · model-written summary
The Pi concentration in the apoplast was about 0.1 to 1 mol m-3 even without Pi supply, much higher than in the usual soil environment.
- Taxon
- barleyHordeum vulgaret0
- Organ / stage
- apoplaste7
- Outcome
- P i concentration in the apoplaste7
- Direction
- much highere7
- Value
- 0.1 to I molm −3e7
- Comparator
- the usual soil environmente7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“barley leaves”
e7“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”
Claim · model-written summary
The authors suggest that Pi absorbed by root cells is concentrated during transport from the root to the leaf apoplast.
- Taxon
- barleyHordeum vulgaret0
- Organ / stage
- root cellse0
- Outcome
- concentrated in the transport processe0
- Qualifier
- transport process from the root to the leaf apoplaste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“barley leaves”
e0“the P i absorbed by root cells is concentrated in the transport process from the root to the leaf apoplast”
Claim · model-written summary
The Pi content of the xylem exudate was constant irrespective of growth culture conditions.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- growth culture conditionse1
- Outcome
- content of P i in the xylem exudatee1
- Direction
- constante1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“barley leaves”
e1“The content of P i in the xylem exudate was constant irrespective of growth culture conditions”
Claim · model-written summary
The authors propose that the root may function as the constant Pi supplier to the above-ground tissues.
- Taxon
- barleyHordeum vulgaret0
- Organ / stage
- roote2
- Outcome
- constant P i suppliere2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“barley leaves”
e2“The root may be functioning as the constant P i supplier to the above tissues”