We tested the effect of growing conditions during micropropagation on the fast kinetics of chlorophyll (Chl) fluorescence of Gardenia jasminoides Ellis plantlets during a 4-week acclimation to ex vitro. We studied whether photoautotrophic growing in vitro produced plantlets with less photoinhibition impairment during acclimation. Of the growing conditions stimulating photoautotrophy in vitro, only loose tube caps had a positive effect, whereas low sucrose or sucrose-free content in the medium and high PPFD showed a negative effect. Thus, plantlets cultured with 3 % (m/v) of sucrose were subsequently less photoinhibited throughout acclimation than those cultured with low sucrose (0.5 %) or sucrose-free media. Moreover, at the end of acclimation the former plantlets showed Fv/Fm and Fv/F0 ratios typical of unstressed ex vitro plants as well as a higher Chl content and ratio of Chls to carotenoids. Plantlets cultured at a photosynthetic photon fluence density (PPFD) of 50 µmol m-2 s-1 also showed a better performance at the end of acclimation than those cultured at a higher (110 µmol m-2 s-1) PPFD. Thus except in the case of loose-tube closure, gardenia plantlets cultured in vitro under conventional sucrose concentration and PPFD are the least photoinhibited during acclimation. Nevertheless, significant interactions between the in vitro growing factors were observed at the end of acclimation. and M. D. Serret, M. I. Trillas, J. L. Araus.
High irradiance promotes decreases in the quantum yield in plants, which reduce the photosynthetic rate. The excess of light in combination with water deficit can intensify the response of plants to stress, especially in species susceptible to those factors. The aim of the present study was to characterize the photosynthetic activity of young jatobá-do-cerrado (Hymenaea stigonocarpa Mart. ex Hayne) trees under different irradiance conditions, both alone and/or in combination with water deficit. Four irradiances [45, 230, 510, and 1,700 μmol(photon) m-2 s-1] and two levels of water in soil (90% and 50% of field capacity) were used. Gas exchange, water potential, and chlorophyll a fluorescence were measured. The highest rates of photosynthesis were observed under irradiances of 230 and 510 μmol(photon) m-2 s-1. Irradiance of 1,700 μmol(photon) m-2 s-1 led to the photoinhibition of photosynthesis, as indicated by a reduced maximum quantum yield of PSII, effective quantum yield ratio, and electron transport rate, as well as higher nonphotochemical quenching. The most stressful to young H. stigonocarpa plants was high irradiance, while water deficit did not intensify the response to light stress., A. C. Costa, S. L. Rezende-Silva, C. A. Megguer, L. M. F. Moura, M. Rosa, A. A. Silva., and Obsahuje bibliografii
Significantly lower Hill reaction activity together with greater sensitivity to photoinhibitory conditions was observed at various irradiances in atrazine-resistant biotypes of Senecio vulgaris L., Amaranthus retroflexus L., and Poa annua L. compared to the susceptible ones. and M. Körnerová, D. Holá, D. Chodová.
After a S-d cultivatíon in Solutions of different concentrations of lead and copper, structiiral changes were established in the photosynthetic apparatus of Elodea canadensis Rich. Lead and low concentrations of copper (0.03, 0.06 and 0.25 g m’^) did not induce large structural transformations in the protoplast. Some of the changes were specific for the species; vacuolization of the cytoplasm, instability of the tonoplast, increased activity of the dictyosomes, abnormally active division of the mitochondria, and number of chloroplasts and mitochondria in definite cell zones. High concentrations of copper (0.5, 1 and 1.5 g m*^) induced within 5 d a generál destruction of the protoplast. The concentration of 0.5 g(Cu^0 threshold concentration for survival of this species. High quantities of both metals were accumulated in the treated plants.
For the first time the expression of C3 and CAM in the leaves of different age of Marrubium frivaldszkyanum Boiss, is reported. With increasing leaf age a typical C3 photosynthesis pattern and high transpiration rate were found. In older leaves a shift to CAM occurred and the 24-h transpiration water loss decreased. A correlation was established between leaf area and accumulation of malate. Water loss at early stages of leaf expansion may be connected with the shift to CAM and the water economy of the whole plant. and Y. K. Markovska, D. S. Dimitrov.
Young plants of maize inbred lines CE777, CE704, and CE810 and their F1 hybrids displaying a positive heterotic effect in various photosynthetic characteristics were exposed to low temperature during their early growth developmental stage. The photochemical activity of isolated mesophyll chloroplasts and the contents of photosynthetic pigments in leaves of stressed and non-stressed plants were compared with the aim to find out the possible changes in the relationship between parents and hybrids, and to determine the genetic basis of heterosis in F1 generation. Strong decrease in the content of chlorophylls was observed for all genotypes examined when plants were subjected to low growth temperature. Similar change was recorded for Hill reaction activity (HRA) of inbred lines but not of their F1 hybrids, and no significant response at all was found for photosystem 1 (PS1) activity or the total carotenoids content. The intraspecific variation due to differences between genotypes was found for most of photosynthetic characteristics examined. This variation was caused by the additive and dominance genetic effects. Positive dominance was the main cause of positive heterosis in HRA and in the contents of photosynthetic pigments and was much more pronounced in the stressed plants compared to the non-stressed ones. The maternal additive effects participated in the inheritance of contents of photosynthetic pigments in plants exposed to low temperature, too. and M. Körnerová, D. Holá.
Water availability is the main factor limiting crop growth and productivity in dry regions. This study was carried out in order to determine the effect of spraying methanol solution on the photosynthetic characteristics of bean plants. The main aim of our experiment was to improve plant performance under stress caused by water shortage. Two factors were involved: water-deficit stress, such as severe stress (25% of field capacity), mild stress (75% of field capacity), and no stress (100% of field capacity), and application of methanol solution spray at four concentrations: control (without spraying), 10, 20, and 30%. Methanol was applied three times at different growth stages (seedling, flowering, and podding stage) in 10-d intervals. The treatment with 20% methanol at the seedling stage resulted in increased net photosynthesis (P N), intercellular CO2 concentration (C i), and decreased transpiration rate (E) under no stress and mild stress conditions. Under severe stress, 10 and 20%-methanol treatments resulted in increased C i, maximal quantum yield of PSII photochemistry, and decreased E. At the flowering stage, methanol treatments resulted in decreased E and increased C i under mild and severe stress. At the podding stage, 10 and 20%-methanol treatments resulted in increased P N, C i, and total chlorophyll content under mild stress. In conclusion, we suggested that foliar application of methanol had a positive role in enhancing photosynthetic performance., N. Armand, H. Amiri, A. Ismaili., and Obsahuje seznam literatury
We studied the relationships between the degree of photoautotrophy, photosynthetic capacity, and extent of photoinhibition of Gardenia jasminoides Ellis plantlets in vitro. Two successive micropropagation stages (shoot multiplication and root induction), and three culture conditions [tube cap closure, photosynthetic photon flux density (PPFD), and sucrose concentration] which may influence the development of photoautotrophy in vitro were assayed. The ratios of variable chlorophyll fluorescence to either maximal (Fv/Fm) or ground (Fv/F0) values were low, irrespective of the culture stage or growing conditions. Incomplete development of the photosynthetic apparatus and permanent photoinhibition may be involved. However, Fv/Fm and Fv/F0 increased from shoot multiplication to root induction owing to a decrease in F0 and an increase in Fm. This suggests that photoinhibition decreases later during micropropagation, when the photoautotrophy of plantlets is more advanced. The low sucrose content and high PPFD increased the photoinhibition of plantlets, whereas growth in tubes with permeable caps showed the opposite effect. The only culture factor with a significant (positive) effect on maximum photosynthetic rate (Pmax) was PPFD. At shoot multiplication net photosynthetic rate (PN) was positively correlated with the half time of the increase from F0 to Fm (t1/2). Such association may be mainly due to a common response of both traits to higher PPFD in culture. Within each culture stage, no relationship was observed between PN and the degree of photoautotrophy, which was positively correlated with Fv/Fm and Fv/F0 during root induction. During shoot multiplication, these correlations were not significant, or were even negative. Hence during the last stage of micropropagation, plantlets with a higher degree of photoautotrophy are less photoinhibited, whereas they do not follow this pattern at the earlier stage. and M. D. Serret ... [et al.].
The optimum temperature for photosynthetic CO2 assimilation of A. mangium phyllodes was 30-32 °C. Photosystem 2 (PS 2) exhibited high tolerance to high temperature. Gas exchange and the function of PS2 of A. mangium were adapted to the temperature regime of the tropical environment and this might be the contributing factor to their fast growth under tropical conditions. and Hua Yu, Bee-Lian Ong.
10-d-old pea plants {Pisum sativum L. cv. Ran 1) were treated for 24 h with proline (10-6 M oř 10*5 M) before salinization with 50 mM NaCl for 2 d. Salt stress resulted in an increase of endogenous ffee proline content, CO2 compensation concentration, photorespiration and glycollate oxidase activity; net photosynthetic rate (P^) was inhibited, but dark respiration rate (Pp) was not affected. •‘♦CO2 fixation by protoplasts isolated from salt stressed plants was inhibited by 60 %, however, the *‘*C02 fixation by protoplasts, isolated firom plants treated with proline before salinization, was only slightly reduced by NaCl. Proline alleviated the inhibitory effect of NaCl in a concentration-depending manner. Pre-treatment with proline decreased Na+ and CP accumulation in the shoot; the root content of these ions was increased.