Abstract
Aims Our objective was to investigate the light-adaptive physiological mechanism of maize on shading stress after anthesis, in order to provide theory behind evidence for high and stable yield in summer maize. Methods In a field experiment, we used common corn (Zea mays) (TY2) to analyze changes of photosynthetic performance, chlorophyll fluorescence parameters, xanthin circle and light partition in maize in the process of shading and recovery stages under (a) shading 55% (+S) 1–20 d after pollination and (b) natural illumination in field condition (–S). Important findings The net photosynthetic rate and light saturation point of ear leaves declined rapidly, because the chlorophyll content, soluble protein content and PEPCase and RuBPCase activities in ear leaves markedly decreased after shading. Under shading, the maximal photochemical efficiency (Fv/Fm) and the actual photo-chemical efficiency (ФPSII) significantly declined, but non-photochemistry quenching (NPQ) increased. The ФPSII of ear leaves increased in early recovery, which indicated that the sudden exposure to natural light significantly enhanced the photosynthetic electron transport rate, according with its photosynthetic rate and carbon metabolism activity of maize ear leaves. After shading, the size of xanthin circle sink in ear leaves was not significantly dif-ferent, but the de-epoxidation state of xanthin circle (A + Z)/(V + A + Z) increased after shading. The distribution of light energy in photochemical reaction was lower, but the antenna dissipation rate of light energy increased sig-nificantly. On the other hand, the dissipation of excess light energy in the recovery process mainly depended on non-photochemical reactions. The PSII primary photochemistry activity of maize decreased under after shading and recovery in early stage, which limited electron supply of photosynthetic carbon metabolism and re- strained the photosynthesis. Then the energy dissipation mostly relied on the xanthin circle increased. The light protective mechanism of maize leaves improved in adaptation to the natural light, and photosynthetic capability gradually recovered after illumination switch.
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Claims 11
Claim · model-written summary
Shading rapidly reduced ear-leaf net photosynthetic rate and light saturation point.
- Organ / stage
- ear leavese0
- Treatment
- shadingt0
- Outcome
- net photosynthetic rate and light saturation pointe0
- Direction
- declinede0
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The net photosynthetic rate and light saturation point of ear leaves declined rapidly”
t0“Physiological mechanism of shading stress on photosynthetic efficiency in summer maize (Zea mays)”
Claim · model-written summary
Shading markedly decreased chlorophyll and soluble protein content and PEPCase and RuBPCase activities in ear leaves.
- Organ / stage
- ear leavese0
- Treatment
- shadinge0
- Outcome
- chlorophyll content, soluble protein content and PEPCase and RuBPCase activitiese0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chlorophyll content, soluble protein content and PEPCase and RuBPCase activities in ear leaves markedly decreased after shading”
t0“Physiological mechanism of shading stress on photosynthetic efficiency in summer maize (Zea mays)”
Claim · model-written summary
Shading significantly reduced Fv/Fm and ФPSII.
- Treatment
- shadinge0
- Outcome
- maximal photochemical efficiency (Fv/Fm) and the actual photo-chemical efficiency (ФPSII)e0
- Direction
- declinede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under shading, the maximal photochemical efficiency (Fv/Fm) and the actual photo-chemical efficiency (ФPSII) significantly declined”
t0“Physiological mechanism of shading stress on photosynthetic efficiency in summer maize (Zea mays)”
Claim · model-written summary
Shading increased NPQ.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“non-photochemistry quenching (NPQ) increased”
t0“Physiological mechanism of shading stress on photosynthetic efficiency in summer maize (Zea mays)”
Claim · model-written summary
Ear-leaf ФPSII increased early in recovery.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The ФPSII of ear leaves increased in early recovery”
t0“Physiological mechanism of shading stress on photosynthetic efficiency in summer maize (Zea mays)”
Claim · model-written summary
Xanthin circle sink size did not differ significantly after shading.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After shading, the size of xanthin circle sink in ear leaves was not significantly dif-ferent”
t0“Physiological mechanism of shading stress on photosynthetic efficiency in summer maize (Zea mays)”
Claim · model-written summary
The xanthin circle de-epoxidation state increased after shading.
- Treatment
- shadinge0
- Outcome
- de-epoxidation state of xanthin circle (A + Z)/(V + A + Z)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the de-epoxidation state of xanthin circle (A + Z)/(V + A + Z) increased after shading”
t0“Physiological mechanism of shading stress on photosynthetic efficiency in summer maize (Zea mays)”
Claim · model-written summary
Photochemical light-energy distribution was lower after shading.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The distribution of light energy in photochemical reaction was lower”
t0“Physiological mechanism of shading stress on photosynthetic efficiency in summer maize (Zea mays)”
Claim · model-written summary
Antenna light-energy dissipation increased significantly.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the antenna dissipation rate of light energy increased sig-nificantly”
t0“Physiological mechanism of shading stress on photosynthetic efficiency in summer maize (Zea mays)”
Claim · model-written summary
Early shading and recovery reduced PSII primary photochemistry activity, limiting electron supply and photosynthesis.
- Outcome
- PSII primary photochemistry activitye0
- Direction
- decreasede0
- Qualifier
- limited electron supply of photosynthetic carbon metabolisme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The PSII primary photochemistry activity of maize decreased under after shading and recovery in early stage, which limited electron supply of photosynthetic carbon metabolism and re- strained the photosynthesis”
t0“Physiological mechanism of shading stress on photosynthetic efficiency in summer maize (Zea mays)”
Claim · model-written summary
Photosynthetic capability gradually recovered after the illumination switch.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic capability gradually recovered after illumination switch”
t0“Physiological mechanism of shading stress on photosynthetic efficiency in summer maize (Zea mays)”
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