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Numerous studies show that photosynthesis in non-foliar tissues contributes to plant productivity. Here, we demonstrate that in chlorenchyma tissues of lignified branches of grape vines, photosynthetic activity is maintained during winter and provide evidence that corticular photosynthesis could contribute to the plant’s freeze tolerance. In a collection of grape varieties that varied noticeably in freeze tolerance, a positive correlation between the maximum quantum yield of photosystem II in the wintering vines and the ability to survive harsh winter temperatures was observed. A more detailed comparison of two grapevine varieties differing in freeze tolerance showed that the vines of the more tolerant variety have more abundant corticular chlorenchyma with chloroplasts containing a better developed network of photosynthetic membranes, characterized by a higher photosynthetic pigments content, higher efficiency of both photosystems, and higher mobility of antennae complexes under the changing light intensity. In addition, we found that freezing temperatures induced more damage in vine samples when they were preliminarily treated with a specific inhibitor of photosynthetic electron transfer. The data obtained could be useful in the generation of freeze-tolerant grape varieties.

The knockout of the At2g28210 gene encoding α-carbonic anhydrase 2 (α-CA2) in Arabidopsis thaliana (Columbia) led to alterations in photosynthetic processes. The effective quantum yields of both photosystem II (PSII) and photosystem I (PSI) were higher in α-carbonic anhydrase 2 knockout plants (α-CA2-KO), and the reduction state of plastoquinone pool was lower than in wild type (WT). The electron transport rate in the isolated thylakoids measured with methyl viologen was higher in α-CA2-KO plants. The amounts of reaction centers of PSII and PSI were similar in WT and α-CA2-KO plants. The non-photochemical quenching of chlorophyll a fluorescence in α-CA2-KO leaves was lower at the beginning of illumination, but became slightly higher than in WT leaves when the steady state was achieved. The degree of state transitions in the leaves was lower in α-CA2-KO than in WT plants. Measurements of the electrochromic carotenoid absorbance shift (ECS) revealed that the light-dependent pH gradient (ΔpH) across the thylakoid membrane was lower in the leaves of α-CA2-KO plants than in WT plants. The starch content in α-CA2-KO leaves was lower than in WT plants. The expression levels of the genes encoding chloroplast CAs in α-CA2-KO changed noticeably, whereas the expression levels of genes of cytoplasmic CAs remained almost the same. It is proposed that α-CA2 may be situated in the chloroplasts.

The carbonic anhydrase (CA) activities of the preparations of cytoplasm, mitochondria, chloroplast stroma, and chloroplast thylakoids, as well as the expression levels of genes encoding αCA1, αCA2, αCA4, βCA1, βCA2, βCA3, βCA4, βCA5, and βCA6, were measured in the leaves of Arabidopsis thaliana plants, acclimated to different CO2 content in the air: low (150 ppm, lCO2), normal (450 ppm, nCO2), and high (1200 ppm, hCO2). To evaluate the photosynthetic apparatus operation, the carbon assimilation and chlorophyll a fluorescence were measured under the same conditions. It was found that the CA activities of the preparations of cytoplasm, chloroplast stroma, and chloroplast thylakoids measured after two weeks of acclimation were higher, the lower CO2 concentration in the air. That was preceded by an increase in the expression levels of genes encoding the cytoplasmic form of βCA1, and other cytoplasmic CAs, βCA2, βCA3, and βCA4, as well as of the chloroplast CAs, βCA5, and the stromal forms of βCA1 in a short-term range 1–2 days after the beginning of the acclimation. The dependence on the CO2 content in the air was most noticeable for the CA activity of the preparations of the stroma; it was two orders higher in lCO2 plants than in hCO2 plants. The CA activity of thylakoid membranes from lCO2 plants was higher than that in nCO2 and hCO2 plants; however, in these plants, a significant increase in the expression levels of the genes encoding αCA2 and αCA4 located in thylakoid membranes was not observed. The CA activity of mitochondria and the expression level of the mitochondrial βCA6 gene did not depend on the content of carbon dioxide. Taken together, the data implied that in the higher plants, the supply of inorganic carbon to carboxylation sites is carried out with the cooperative functioning of CAs located in the cytoplasm and CAs located in the chloroplasts.