Abstract
Abstract Stress‐induced senescence is frequently alluded to, but interactive effects of water and N deficits on leaf longevity and on physiological changes associated with leaf aging have received little attention. A 2‐yr field experiment with maize ( Zea mays L.) was conducted on Yolo loam (fine‐silty, mixed, nonacid, thermic Typic Xerorthents) with four treatments: N fertilized (180 kg N/ha) with (NI) and without (ND) irrigation; and no N applied with (OI) and without (OD) irrigation. Size and longevity measurements were made of leaves at all nodal positions, and leaves 5, 11, and 15 (counting up from stem base) were monitored for changes in photosynthetic capacity (PC), N concentration, and chlorophyll content (CHL). Leaf PC was correlated with percent N during senescence in all treatments ( r 2 = 0.86), but an occasional midday depression in PC, unrelated to leaf N status, was observed in severely water stressed plants. Chlorophyll and percent N were also correlated ( r 2 = 0.80), but initial onsets of decline in these two parameters often differed by several days. Nitrogen deficits were less severe in 1983 than 1982, but in both years lack of applied N had an early impact and reduced longevity of lower leaves. In 1982, N deficiency caused a 50% reduction in leaf peak values of percent N, CHL, and PC, and the decline in leaf 5 was most rapid in low N plants. Water stress intensified as stored soil water was gradually depleted, and the most rapid decline and earliest complete senescence of upper leaves (11 and 15) occurred in the ND treatment. These results indicate that early stress effects on leaf area and ear development affected subsequent demands for water and N, which in turn altered patterns of leaf senescence.
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Claims 13
Claim · model-written summary
Photosynthetic capacity correlated with leaf nitrogen percentage during senescence.
Zea maysNot reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf PC was correlated with percent N during senescence in all treatments ( r 2 = 0.86)”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Severely water stressed plants occasionally had midday photosynthetic depression unrelated to leaf nitrogen.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an occasional midday depression in PC, unrelated to leaf N status, was observed in severely water stressed plants”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Chlorophyll and leaf nitrogen percentage correlated.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Chlorophyll and percent N were also correlated ( r 2 = 0.80)”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Initial declines in chlorophyll and nitrogen often started several days apart.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“initial onsets of decline in these two parameters often differed by several days”
e1“Chlorophyll and percent N were also correlated”
e2“maize ( Zea mays L.)”
Claim · model-written summary
Nitrogen deficits were less severe in 1983 than 1982.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen deficits were less severe in 1983 than 1982”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Lack of nitrogen application reduced lower leaf longevity in both years.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in both years lack of applied N had an early impact and reduced longevity of lower leaves”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Nitrogen deficiency reduced peak leaf nitrogen percentage by 50% in 1982.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In 1982, N deficiency caused a 50% reduction in leaf peak values of percent N, CHL, and PC”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Nitrogen deficiency reduced peak chlorophyll by 50% in 1982.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In 1982, N deficiency caused a 50% reduction in leaf peak values of percent N, CHL, and PC”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Nitrogen deficiency reduced peak photosynthetic capacity by 50% in 1982.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In 1982, N deficiency caused a 50% reduction in leaf peak values of percent N, CHL, and PC”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Leaf 5 declined fastest in low nitrogen plants.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the decline in leaf 5 was most rapid in low N plants”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Water stress intensified as stored soil water depleted.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Water stress intensified as stored soil water was gradually depleted”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Nonirrigated nitrogen-fertilized plants had the fastest decline and earliest senescence of upper leaves.
- Organ / stage
- upper leaves (11 and 15)e0
- Treatment
- ND treatmente0
- Outcome
- complete senescence of upper leavese0
- Direction
- earlieste0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the most rapid decline and earliest complete senescence of upper leaves (11 and 15) occurred in the ND treatment”
e1“N fertilized (180 kg N/ha) with (NI) and without (ND) irrigation”
e2“maize ( Zea mays L.)”
Claim · model-written summary
Early stress effects on leaf area and ear development altered later water and nitrogen demand and leaf senescence.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“early stress effects on leaf area and ear development affected subsequent demands for water and N, which in turn altered patterns of leaf senescence”
e1“maize ( Zea mays L.)”
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