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Photochemical and antioxidative responses of the glume and flag leaf to seasonal senescence in wheat.

Kong L, Sun M, Xie Y, Wang F, Zhao Z - Front Plant Sci (2015)

Bottom Line: In the present study, an experiment was conducted to investigate the anatomy, chloroplast temporal changes, chlorophyll fluorescence, xanthophyll cycle and antioxidative defense system in glumes of field-grown wheat during grain filling compared with flag leaves.In addition, the glumes exhibited a higher antioxidant enzyme activity and a lower accumulation of reactive oxygen species.These results suggest that the glumes are photosynthetically active and senesce later than the flag leaves; the advantages may have been achieved by coordinated contributions of the structural features, higher NPQ levels, greater de-epoxidation of the xanthophyll cycle components and antioxidative defense metabolism.

View Article: PubMed Central - PubMed

Affiliation: Crop Research Institute, Shandong Academy of Agricultural Sciences , Jinan, China.

ABSTRACT
The non-leaf photosynthetic organs have recently attracted much attention for the breeding and screening of varieties of cereal crops to achieve a high grain yield. However, the glume photosynthetic characteristics and responses to high temperature at the late stages of grain filling are not well known in winter wheat (Triticum aestivum L.). In the present study, an experiment was conducted to investigate the anatomy, chloroplast temporal changes, chlorophyll fluorescence, xanthophyll cycle and antioxidative defense system in glumes of field-grown wheat during grain filling compared with flag leaves. Observations using a light microscope revealed that the glumes developed a solid structural base for performing photosynthesis. Compared with the flag leaves, the glumes preserved a more integral ultrastructure, as observed under transmission electron microscopy, and had higher values of Fv/Fm and ΦPSII at the maturity stage. Further analysis of the chlorophyll fluorescence demonstrated that the glumes experienced high non-photochemical quenching (NPQ) at the late stages. Determination of the pool size of the xanthophyll cycle suggested that the (A+Z)/(V+A+Z) ratio was consistently higher in glumes than in flag leaves and that the V+A+Z content was considerably higher in glumes at the maturity stage. In addition, the glumes exhibited a higher antioxidant enzyme activity and a lower accumulation of reactive oxygen species. These results suggest that the glumes are photosynthetically active and senesce later than the flag leaves; the advantages may have been achieved by coordinated contributions of the structural features, higher NPQ levels, greater de-epoxidation of the xanthophyll cycle components and antioxidative defense metabolism.

No MeSH data available.


Related in: MedlinePlus

Changes in the xanthophyll cycle pool size, i.e., contents of V+A+Z (A), and the de-epoxidation state of the xanthophyll cycle, i.e., the (A+Z)/(V+A+Z) ratio (B). Columns with different letters are significantly different according to Duncan’s multiple range test using DPS software (P < 0.05). The P value for comparison between flag leaf and glume at each stage is presented over the top of column. The values are the means ± SD from three independent measurements.
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Figure 5: Changes in the xanthophyll cycle pool size, i.e., contents of V+A+Z (A), and the de-epoxidation state of the xanthophyll cycle, i.e., the (A+Z)/(V+A+Z) ratio (B). Columns with different letters are significantly different according to Duncan’s multiple range test using DPS software (P < 0.05). The P value for comparison between flag leaf and glume at each stage is presented over the top of column. The values are the means ± SD from three independent measurements.

Mentions: Figure 5 shows the changes in the pool size of the xanthophyll cycle, i.e., violaxanthin (V) + zeaxanthin (Z) + antheraxanthin (A), and the conversion state of the xanthophyll cycle, i.e., the ratio of (A+Z) to (V+A+Z), in the flag leaves and glumes during grain filling. The pool size of the xanthophyll cycle in the glumes was significantly lower than that in the flag leaves at 0, 8, 16, and 24 DAA. However, contrary to the marked decreases observed in the flag leaves, the overall content of xanthophylls was significantly increased in the glumes at 32 DAA and was thus significantly higher in the glumes than in the flag leaves (Figure 5A). The extent of the de-epoxidation of the pigment interconversion within the xanthophyll cycle can be described by the (Z+A)/(V+Z+A) ratio. This ratio increased continually in both tissues during grain filling as the air temperature continually increased (Figures 5B and 2S). In glumes, the (Z+A)/(V+Z+A) ratio was consistently and significantly higher than that in the flag leaves (Figure 5B; Table 2).


Photochemical and antioxidative responses of the glume and flag leaf to seasonal senescence in wheat.

Kong L, Sun M, Xie Y, Wang F, Zhao Z - Front Plant Sci (2015)

Changes in the xanthophyll cycle pool size, i.e., contents of V+A+Z (A), and the de-epoxidation state of the xanthophyll cycle, i.e., the (A+Z)/(V+A+Z) ratio (B). Columns with different letters are significantly different according to Duncan’s multiple range test using DPS software (P < 0.05). The P value for comparison between flag leaf and glume at each stage is presented over the top of column. The values are the means ± SD from three independent measurements.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440901&req=5

Figure 5: Changes in the xanthophyll cycle pool size, i.e., contents of V+A+Z (A), and the de-epoxidation state of the xanthophyll cycle, i.e., the (A+Z)/(V+A+Z) ratio (B). Columns with different letters are significantly different according to Duncan’s multiple range test using DPS software (P < 0.05). The P value for comparison between flag leaf and glume at each stage is presented over the top of column. The values are the means ± SD from three independent measurements.
Mentions: Figure 5 shows the changes in the pool size of the xanthophyll cycle, i.e., violaxanthin (V) + zeaxanthin (Z) + antheraxanthin (A), and the conversion state of the xanthophyll cycle, i.e., the ratio of (A+Z) to (V+A+Z), in the flag leaves and glumes during grain filling. The pool size of the xanthophyll cycle in the glumes was significantly lower than that in the flag leaves at 0, 8, 16, and 24 DAA. However, contrary to the marked decreases observed in the flag leaves, the overall content of xanthophylls was significantly increased in the glumes at 32 DAA and was thus significantly higher in the glumes than in the flag leaves (Figure 5A). The extent of the de-epoxidation of the pigment interconversion within the xanthophyll cycle can be described by the (Z+A)/(V+Z+A) ratio. This ratio increased continually in both tissues during grain filling as the air temperature continually increased (Figures 5B and 2S). In glumes, the (Z+A)/(V+Z+A) ratio was consistently and significantly higher than that in the flag leaves (Figure 5B; Table 2).

Bottom Line: In the present study, an experiment was conducted to investigate the anatomy, chloroplast temporal changes, chlorophyll fluorescence, xanthophyll cycle and antioxidative defense system in glumes of field-grown wheat during grain filling compared with flag leaves.In addition, the glumes exhibited a higher antioxidant enzyme activity and a lower accumulation of reactive oxygen species.These results suggest that the glumes are photosynthetically active and senesce later than the flag leaves; the advantages may have been achieved by coordinated contributions of the structural features, higher NPQ levels, greater de-epoxidation of the xanthophyll cycle components and antioxidative defense metabolism.

View Article: PubMed Central - PubMed

Affiliation: Crop Research Institute, Shandong Academy of Agricultural Sciences , Jinan, China.

ABSTRACT
The non-leaf photosynthetic organs have recently attracted much attention for the breeding and screening of varieties of cereal crops to achieve a high grain yield. However, the glume photosynthetic characteristics and responses to high temperature at the late stages of grain filling are not well known in winter wheat (Triticum aestivum L.). In the present study, an experiment was conducted to investigate the anatomy, chloroplast temporal changes, chlorophyll fluorescence, xanthophyll cycle and antioxidative defense system in glumes of field-grown wheat during grain filling compared with flag leaves. Observations using a light microscope revealed that the glumes developed a solid structural base for performing photosynthesis. Compared with the flag leaves, the glumes preserved a more integral ultrastructure, as observed under transmission electron microscopy, and had higher values of Fv/Fm and ΦPSII at the maturity stage. Further analysis of the chlorophyll fluorescence demonstrated that the glumes experienced high non-photochemical quenching (NPQ) at the late stages. Determination of the pool size of the xanthophyll cycle suggested that the (A+Z)/(V+A+Z) ratio was consistently higher in glumes than in flag leaves and that the V+A+Z content was considerably higher in glumes at the maturity stage. In addition, the glumes exhibited a higher antioxidant enzyme activity and a lower accumulation of reactive oxygen species. These results suggest that the glumes are photosynthetically active and senesce later than the flag leaves; the advantages may have been achieved by coordinated contributions of the structural features, higher NPQ levels, greater de-epoxidation of the xanthophyll cycle components and antioxidative defense metabolism.

No MeSH data available.


Related in: MedlinePlus