Abstract
BACKGROUND AND AIMS: New maize (Zea mays) hybrids outperformed old ones even at reduced N rates. Understanding the mechanisms of the differences in performance between newer and older hybrids under N deficiency could provide avenues for breeding maize cultivars with large yield under N deficiency, and reduce environmental pollution caused by N fertilizers. METHODS: N deficiency effects on grain weight, plant weight, harvest index, leaf area and photosynthetic traits were studied in the field for six maize hybrids released during the past 50 years to compare their tolerance and to explore their physiological mechanisms. KEY RESULTS: N deficiency decreased grain yield and plant weight in all hybrids, especially in the older hybrids. However, there was no significant difference in harvest index, rate of light-saturated photosynthesis (Psat) 20 d before flowering, leaf area or plant weight at flowering between the N-deficient and control plants of all hybrids. Dry matter production after flowering of the N-deficient plants was significantly lower than that of the control plants in all hybrids, especially in the older hybrids, and was mostly due to differences in the rate of decrease in photosynthetic capacity during this stage. The lower Psat of the older hybrids was not due to stomatal limitation, as there was no significant difference in stomatal conductance (gs) and intercellular CO2 concentration (Ci) between the hybrids. N deficiency accelerated senescence, i.e. decreased chlorophyll and soluble protein contents, after anthesis more for the earlier released hybrids than for the later ones. N deficiency decreased phosphoenolpyruvate carboxylase (PEPCase) activity significantly more in older hybrids than newer hybrids, and affected the maximal efficiency of PSII photochemistry (Fv/Fm) only in the old hybrids and at the late stage. CONCLUSIONS: Compared with older (earlier released) hybrids, newer (later released) hybrids maintained greater plant and grain weight under N deficiency because their photosynthetic capacity decreased more slowly after anthesis, associated with smaller non-stomatal limitations due to maintenance of PEPCase activity, and chlorophyll and soluble protein content.
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Claims 10
Claim · model-written summary
Nitrogen deficiency decreased grain yield, especially in older maize hybrids.
- Treatment
- N deficiencye0
- Outcome
- grain yielde0
- Direction
- decreasede0
- Qualifier
- especially in the older hybridse0
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N deficiency decreased grain yield and plant weight in all hybrids, especially in the older hybrids.”
e1“maize (Zea mays) hybrids”
Claim · model-written summary
Nitrogen deficiency decreased plant weight, especially in older maize hybrids.
- Treatment
- N deficiencye0
- Outcome
- plant weighte0
- Direction
- decreasede0
- Qualifier
- especially in the older hybridse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N deficiency decreased grain yield and plant weight in all hybrids, especially in the older hybrids.”
e1“maize (Zea mays) hybrids”
Claim · model-written summary
Harvest index, presflowering light-saturated photosynthesis, leaf area, and flowering plant weight did not differ significantly between nitrogen-deficient and control maize hybrids.
- Treatment
- N-deficiente0
- Outcome
- harvest index, rate of light-saturated photosynthesis (Psat) 20 d before flowering, leaf area or plant weight at floweringe0
- Direction
- no significant differencee0
- Comparator
- control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was no significant difference in harvest index, rate of light-saturated photosynthesis (Psat) 20 d before flowering, leaf area or plant weight at flowering between the N-deficient and control plants of all hybrids”
e1“maize (Zea mays) hybrids”
Claim · model-written summary
Postflowering dry-matter production was significantly lower in nitrogen-deficient maize plants, particularly older hybrids.
- Treatment
- N-deficiente0
- Outcome
- Dry matter production after floweringe0
- Direction
- lowere0
- Qualifier
- especially in the older hybridse0
- Comparator
- control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dry matter production after flowering of the N-deficient plants was significantly lower than that of the control plants in all hybrids, especially in the older hybrids”
e1“maize (Zea mays) hybrids”
Claim · model-written summary
Differences in postflowering dry-matter production were mostly attributed to the rate of decline in photosynthetic capacity.
- Outcome
- Dry matter production after floweringe1
- Qualifier
- differences in the rate of decrease in photosynthetic capacity during this stagee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“was mostly due to differences in the rate of decrease in photosynthetic capacity during this stage”
e1“Dry matter production after flowering of the N-deficient plants”
e2“maize (Zea mays) hybrids”
Claim · model-written summary
Older maize hybrids had lower light-saturated photosynthesis without significant differences in stomatal conductance or intercellular CO2 concentration between hybrids.
- Material
- older hybridse0
- Outcome
- Psate0
- Direction
- lowere0
- Qualifier
- no significant difference in stomatal conductance (gs) and intercellular CO2 concentration (Ci) between the hybridse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The lower Psat of the older hybrids was not due to stomatal limitation, as there was no significant difference in stomatal conductance (gs) and intercellular CO2 concentration (Ci) between the hybrids.”
e1“maize (Zea mays) hybrids”
Claim · model-written summary
Nitrogen deficiency accelerated postanthesis senescence more in older than newer maize hybrids, reducing chlorophyll and soluble protein contents.
- Treatment
- N deficiencye0
- Outcome
- chlorophyll and soluble protein contentse0
- Direction
- decreasede0
- Qualifier
- after anthesis more for the earlier released hybridse0
- Comparator
- later onese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N deficiency accelerated senescence, i.e. decreased chlorophyll and soluble protein contents, after anthesis more for the earlier released hybrids than for the later ones.”
e1“maize (Zea mays) hybrids”
Claim · model-written summary
Nitrogen deficiency reduced PEPCase activity significantly more in older than newer maize hybrids.
- Treatment
- N deficiencye0
- Outcome
- phosphoenolpyruvate carboxylase (PEPCase) activitye0
- Direction
- decreasede0
- Comparator
- newer hybridse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N deficiency decreased phosphoenolpyruvate carboxylase (PEPCase) activity significantly more in older hybrids than newer hybrids”
e1“maize (Zea mays) hybrids”
Claim · model-written summary
Nitrogen deficiency affected PSII photochemical efficiency only in old maize hybrids at a late stage.
- Treatment
- N deficiencye1
- Outcome
- maximal efficiency of PSII photochemistry (Fv/Fm)e0
- Qualifier
- only in the old hybrids and at the late stagee0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“affected the maximal efficiency of PSII photochemistry (Fv/Fm) only in the old hybrids and at the late stage”
e1“N deficiency decreased phosphoenolpyruvate carboxylase”
e2“maize (Zea mays) hybrids”
Claim · model-written summary
Newer maize hybrids maintained greater plant and grain weight under nitrogen deficiency than older hybrids.
- Material
- newer (later released) hybridse0
- Outcome
- plant and grain weighte0
- Direction
- greatere0
- Qualifier
- under N deficiencye0
- Comparator
- older (earlier released) hybridse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with older (earlier released) hybrids, newer (later released) hybrids maintained greater plant and grain weight under N deficiency”
e1“maize (Zea mays) hybrids”
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This paper is about lacking the nutrient, so it counts the other way round here.
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See all 2,185 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.