Gas-exchange of ears of cereals in response to carbon dioxide and light

Abstract

Data for the maximum carboxylation velocity of ribulose-1,5-biosphosphate carboxylase, Vm, and the maximum rate of whole-chain electron transport, Jm, were calculated according to a photosynthesis model from the CO2 response and the light response of CO2 uptake measured on ears of wheat (Triticum aestivum L. cv. Arkas), oat (Avena sativa L. cv. Lorenz), and barley (Hordeum vulgare L. cv. Aramir). The ratio Jm/Vm is lower in glumes of oat and awns of barley than it is in the bracts of wheat and in the lemmas and paleae of oat and barley. Light-microscopy studies revealed, in glumes and lemmas of wheat and in the lemmas of oat and barley, a second type of photosynthesizing cell which, in analogy to the Kranz anatomy of C4 plants, can be designated as a bundle-sheath cell. In wheat ears, the CO2-compensation point (in the absence of dissimilative respiration) is between those that are typical for C3 and C4 plants.A model of the CO2 uptake in C3-C4 intermediate plants proposed by Peisker (1986, Plant Cell Environ. 9, 627-635) is applied to recalculate the initial slopes of the A(p(c)) curves (net photosynthesis rate versus intercellular partial pressure of CO2) under the assumptions that the Jm/Vm ratio for all organs investigated equals the value found in glumes of oat and awns of barley, and that ribulose-1,5-bisphosphate carboxylase is redistributed from mesophyll to bundle-sheath cells. The results closely match the measured values. As a consequence, all bracts of wheat ears and the inner bracts of oat and barley ears are likely to represent a C3-C4 intermediate type, while glumes of oat and awns of barley represent the C3 type.

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

“…In wheat, the photosynthesis in glumes and awns can provide up to 30% of the total grain carbon ( Parry et al, 2011 ). Moreover, in terms of anatomical features, the glumes may have an intermediate C 3 –C 4 pathway ( Ziegler-Jöns, 1989 ) and a significantly higher activity ratio of PEPC to Rubisco compared with the flag leaves ( Xu et al, 2004 ). In the present study, we found that glumes had mesophyll cells containing chloroplasts and that both the ventral and dorsal sides presented stomata, indicating that the glumes may be photosynthetically active.…”

Identification and Fine Mapping of a White Husk Gene in Barley (Hordeum vulgare L.)

“…In general, the husk is green, which not only protects the flower and grain from pathogens, insects, and external environments, but also is the essential photosynthetic organ to accumulate dry matter of grain [ 2 , 3 ]. Studies have shown that photosynthesis in husk occurs via C3 and C4 pathways, and they can provide carbohydrates and amino acids for grain growth [ 4 , 5 ]. Therefore, the changes in husk color could affect on the compositions of the grain and the yield of barley.…”

Pathways of Photosynthesis in Non-Leaf Tissues

“…The stems of plants are photosynthetic in some species [3]. Even the trunks of some tree species are photosynthetic [13,14]. Stem photosynthesis (corticular or woody tissue photosynthesis) has been shown to contribute to bud growth on defoliation as reported in Prunus, Umbellularia, and Arctostaphylos species, and shading of the trunk and defoliation was reported to reduce growth in these species.…”

“…Stem photosynthesis (corticular or woody tissue photosynthesis) has been shown to contribute to bud growth on defoliation as reported in Prunus, Umbellularia, and Arctostaphylos species, and shading of the trunk and defoliation was reported to reduce growth in these species. Defoliation resulted in 13 C enrichment in sugars in the trunk phloem. This enrichment is consistent with the carbon being sourced from respiration [13].…”

“…Defoliation resulted in 13 C enrichment in sugars in the trunk phloem. This enrichment is consistent with the carbon being sourced from respiration [13]. Respired CO 2 is known to be depleted in 13 C [15].…”