Abstract
A solution culture experiment was conducted to study the effects of continuous and relieved water stress and of nitrogen (N) supply on growth and N content of grain sorghum cv. Texas 610SR. Polyethylene glycol-6000 was used to impose solution osmotic potentials of -0.1, -0.4, and -1.1 MPa over 9 days beginning on day 21. On day 30, half the plants in the -0.4 and -1.1 MPa treatments were returned to solutions with osmotic potentials of -0.1 MPa (relieved water stress regime), while the other half remained at solution osmotic potentials of -0.4 and -1.1 MPa until harvest (continuous water stress regime). Plants were harvested on day 43. Dry matter yields, total plant N content, mean rate of N uptake per unit root weight, and the number of leaves expanded after imposition of solution osmotic potential treatments were decreased significantly by decreases in N supply and solution osmotic potential in the continuous water stress regime. Decreasing the solution osmotic potential in the continuous water stress regime had no effect on mean N concentrations in expanded leaves or in shoots, but increased N concentrations in roots and in stem plus immature leaves. Plants in the relieved water stress regime produced more dry matter, expanded more leaves after day 21, had higher N contents, N concentrations and mean N uptake rates per unit root weight than plants in the continuous stress regime at equivalent levels of solution osmotic potential. Relationships between leaf N concentrations and relative yield of shoots were non-asymptotic for all three index leaves (youngest emerged blade and the two blades immediately below), and this prevented the calculation of meaningful critical N concentrations in any treatment. The results are discussed in relation to effects of intermittent water stress on rainfed sorghum in the field.
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Claims 5
Claim · model-written summary
Lower nitrogen supply and osmotic potential significantly decreased sorghum dry matter yield, total nitrogen, uptake rate, and leaf expansion under continuous stress.
- Taxon
- grain sorghum
Sorghum bicolort0 - Treatment
- decreases in N supply and solution osmotic potentiale0
- Outcome
- Dry matter yields, total plant N content, mean rate of N uptake per unit root weighte0
- Direction
- decreasede0
- Qualifier
- continuous water stress regimee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dry matter yields, total plant N content, mean rate of N uptake per unit root weight, and the number of leaves expanded after imposition of solution osmotic potential treatments were decreased significantly by decreases in N supply and solution osmotic potential in the continuous water stress regime.”
t0“grain sorghum”
Claim · model-written summary
Lower osmotic potential did not change nitrogen concentrations in expanded leaves or shoots during continuous stress.
- Taxon
- grain sorghumSorghum bicolort0
- Treatment
- Decreasing the solution osmotic potentiale0
- Outcome
- mean N concentrations in expanded leaves or in shootse0
- Direction
- no effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Decreasing the solution osmotic potential in the continuous water stress regime had no effect on mean N concentrations in expanded leaves or in shoots”
t0“grain sorghum”
Claim · model-written summary
Lower osmotic potential increased root and stem plus immature-leaf nitrogen concentrations during continuous stress.
- Taxon
- grain sorghumSorghum bicolort0
- Treatment
- Decreasing the solution osmotic potentiale0
- Outcome
- N concentrations in roots and in stem plus immature leavese0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Decreasing the solution osmotic potential in the continuous water stress regime had no effect on mean N concentrations in expanded leaves or in shoots, but increased N concentrations in roots and in stem plus immature leaves.”
t0“grain sorghum”
Claim · model-written summary
Relieved stress increased dry matter, leaf expansion, nitrogen content, nitrogen concentration, and nitrogen uptake rate relative to continuous stress.
- Taxon
- grain sorghumSorghum bicolort0
- Treatment
- relieved water stress regimee0
- Outcome
- dry matter, expanded more leaves after day 21, had higher N contentse0
- Direction
- moree0
- Comparator
- continuous stress regimee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants in the relieved water stress regime produced more dry matter, expanded more leaves after day 21, had higher N contents, N concentrations and mean N uptake rates per unit root weight than plants in the continuous stress regime at equivalent levels of solution osmotic potential.”
t0“grain sorghum”
Claim · model-written summary
Leaf nitrogen concentration versus relative shoot yield relationships were non-asymptotic in all three index leaves, preventing critical nitrogen estimates.
- Taxon
- grain sorghumSorghum bicolort0
- Organ / stage
- index leavese0
- Outcome
- Relationships between leaf N concentrations and relative yield of shootse0
- Direction
- non-asymptotice0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Relationships between leaf N concentrations and relative yield of shoots were non-asymptotic for all three index leaves (youngest emerged blade and the two blades immediately below), and this prevented the calculation of meaningful critical N concentrations in any treatment.”
t0“grain sorghum”
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