RESUMO
The expression of genes of two carbonic anhydrases (CA) belonging to the α-family, α-CA2 and α-CA4 (according to the nomenclature in N. Fabre et al. (2007) Plant Cell Environ., 30, 617-629), was studied in arabidopsis (Arabidopsis thaliana, var. Columbia) leaves. The expression of the At2g28210 gene coding α-CA2 decreased under increase in plant illumination, while the expression of the At4g20990 gene coding α-CA4 increased. Under conditions close to optimal for photosynthesis, in plants with gene At2g28210 knockout, the effective quantum yield of photosystem 2 and the light-induced accumulation of hydrogen peroxide in leaves were lower than in wild type plants, while the coefficient of non-photochemical quenching of leaf chlorophyll a fluorescence and the rate of CO2 assimilation in leaves were higher. In plants with At4g20990 gene knockout, the same characteristics changed in opposite ways relative to wild type. Possible mechanisms of the participation of α-CA2 and α-CA4 in photosynthetic reactions are discussed, taking into account that protons can be either consumed or released in the reactions they catalyze.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Anidrases Carbônicas/metabolismo , Ferredoxinas/metabolismo , Fotossíntese/fisiologia , Complexo de Proteína do Fotossistema II/metabolismo , Folhas de Planta/enzimologia , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Anidrases Carbônicas/genética , Clorofila/genética , Clorofila/metabolismo , Clorofila A , Ferredoxinas/genética , Complexo de Proteína do Fotossistema II/genética , Folhas de Planta/genéticaAssuntos
Arabidopsis/genética , Arabidopsis/metabolismo , Ácido Ascórbico/biossíntese , Peróxido de Hidrogênio/metabolismo , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Genes de Plantas , Luz , Mutação , Monoéster Fosfórico Hidrolases/genética , Monoéster Fosfórico Hidrolases/metabolismo , Fotossíntese , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Protoplastos/metabolismo , Protoplastos/efeitos da radiaçãoRESUMO
Evaluation of maize productivity under different climatic conditions was made by determination of the amount of the incident solar radiation energy in the PAR range, which can be potentially used by plants for photosynthesis. An irradiance, which can be stored in primary photosynthesis, designated as photosynthetic energy, W (ph), was estimated taking into account the action spectra of photosynthesis. Limitation of the W (ph) usage, owing to unfavorable environmental factors was considered. Quantitative evaluation of limitations by two such factors, air temperature and soil water potential, was made by means of the coefficients F(i), which were defined as the ratio between the photosynthetic rate at a given value of a particular environmental factor and that at the optimal value for this factor. The coefficients F(i), were determined from the dependencies of the photosynthesis rate on air temperature and soil water potential as obtained in chamber and field experiments. In general terms, the fraction of W (ph), which can be utilized under a given climatic condition, was named bioclimatic potential, W (pc). In our model, the effect of monodominancy, when strong action of one factor suppresses the influence of any other factor, was considered. In this case, the bioclimatic potential, designated W'(pc), was calculated by multiplying W (ph) times the coefficient F, for the factor which was most limiting during the period of measurement. There was close correlation between values of bioclimatic potential for the period of vegetation, W'(pc,v), and total dry matter. W'(pc,v) use efficiency in the maize crop was also evaluated for five variants of mineral nutrition.