The present study was conducted to study the effect of 24-epibrassinolide (EBL) on changes of plant growth, net photosynthetic rate, carbonic anhydrase (E.C. 4.2.1.1) and nitrate reductase (E.C.1.6.6.1) activities in the leaves of Raphanus sativus L. under the influence of cadmium (Cd) stress. Cd reduced plant growth, photosynthetic pigment levels, net photosynthetic rate and the activities of carbonic anhydrase and nitrate reductase. However seed application of EBL reduced the toxic effect of Cd on plant growth, pigment content, photosynthesis and enzyme activities. The studies clearly demonstrated the ameliorating effect of 24-epibrassinolide in mitigating the toxicity of Cd in plants. and S. Anuradha, S. Seeta Ram Rao.
Plants of Brassica juncea L. cv. T-59 were supplied with 50 or 100 µM nickel (Ni50, Ni100) at 10 d after sowing (DAS), and sprayed with 28-homobrassinolide (HBR) at 20 DAS. The plants treated with Ni alone exhibited reduced growth, net photosynthetic rate, content of chlorophyll, and the activities of nitrate reductase (E.C.1.6.6.1) and carbonic anhydrase (E.C. 4.2.1.1) at observed 40 DAS, whereas, the contents of peroxidase (PER), catalase (CAT), and proline were increased. However, the spray of HBR partially neutralized the toxic effect of Ni on most of the parameters. Moreover, the treatment of HBR in association with either of the Ni concentration boosted the contents of PER and CAT in leaves and that of proline both in leaves and roots. and M. Masidur Alam ... [et al.].
The effect of cytokinins benzylaminopurine (BAP) and thidiazuron on photosynthetic rate and enzyme activities in sugar beet, pea, meadow fescue and reed fescue leaves was studied. Low concentrations (3-10 g nr3) stimulated the net photosynthetic rate, the activities of ribulose-l,5-bisphosphate carboxylase/oxygenase (RuBPCO) and other enzymes of the carboxylation phase of Calvin cycle, i.e. ribose phosphate isomerase and phosphoribulokinase, and the cycle including the NADP-glyceraldehyde phosphate dehydrogenase complex. On the contrary, there was no change in phosphoenolpyruvate carboxylase activity. In treated leaves the quantity of RuBPC increased along with increases in the level of total leaf proteins. Thus cytokinins act, probably, by specific altering of the synthesis of certain proteins. Inducing or stimulating the synthesis of essential proteins involved in photosynthetic processes, cytokinins cause changes in photosynthetic activity.
The effect of a short cold stress in combination with photoinhibition stress, similar to a low temperature and a high irradiance situation during early morning in the spring time, was examined on four maize cultivars common for Belgium, that differ in early vigour. After 1 h of 2 °C and 500 μmol(photon) m-2 s-1, quantum efficiency and maximum photosynthesis rate at saturating irradiance decreased on average by 11 and 8 %, respectively. For one cultivar, Magister, the decrease was the largest: by 23 and 10 %, respectively. For this cultivar it was combined with a decrease of the water vapour conductance after the stress. The decrease of Fv/F0 due to the cold/light stress was dependent on the cold tolerance (early vigour) of the cultivars. Fv/F0 changed with -45.5 and -40.2 % for the cultivars Ardiles and Banguy, respectively (cultivars with a less good early vigour) in comparison to -36.3 and -35.9 % for Fjord and Magister, which have a good early vigour. Also the ratio of total chlorophylls/total carotenoids changed in dependence on cold tolerance of the cultivars. For more cold tolerant cultivars, the relative amount of total carotenoids (x+c) was higher, indicating a higher protective state. Both the parameter Fv/F0 and the ratio of total chlorophylls to total carotenoids can be used to differentiate the cold tolerant cultivars from the cold non-tolerant ones. Fv/F0 has the advantage because its resolving power is larger and the measurement is less expensive than determination of the pigment ratio. and P. Lootens, J. van Waes, L. Carlier.
Diurnal fluctuations in the contents of malate in gametophores of Polytrichum commune Hedw. and Polytrichum piliferum Hedw. were small. In gametophores of Mnium undulatum Hedw. and leaves of Hieracium pilosella L. significant differences were found in the accumulation of malate between day and night. However, no significant diurnal differences were found in the contents of citrate. High irradiance, desiccation, and submergence by water resulted in increases in daily fluctuations of malate, particularly in the gametophores of P. piliferum and leaves of H. pilosella. Accumulation of malate during night may show the adaptation of the studied species to unfavourable conditions caused by stresses. The change in activity of NADP-malic enzyme may characterize a response to stress factors. and A. Rzepka, G. Rut, J. Krupa.
The effect of abscisic acid (ABA) on the net photosynthetic rate the ribulose 1,5-bisphosphate carboxylase (RuBPC) and the phosphoenolpyruvate caiboxylase (PEPC) activities, the chlorophyll (Chl) content and growth of pea plants (Pisum sativum L.) grown under "white" (WR) or blue radiation (BR), were investigated. BR as compared to WR enhanced P^, the activities of examined enzymes, and Chl content. In špite of higher of the plants grown under BR, diy matter of their shoots was lower in comparison with WR. ABA-treated plants grown under both WR and BR showed reduction in Pn- ABA had no effect on the activities of both RuBPC and PEPC and the Chl content. Independent on the radiation quality, ABA reduced stem elongation, but did not affect the biomass of whole shoots.
To determine the effectiveness of rehabilitation on improving ecosystem functions, we examined net photosynthetic rate (PN), tree species composition, soil enzyme activities, and the microclimate (air and soil temperature, relative humidity) of an area on Mt. Makiling that has been rehabilitated and protected from fire for over 12 years. After it was last burned extensively in 1991, restoration was initiated by planting Acacia mangium and Acacia auriculiformis. We selected three areas to study in 2003. Two areas were rehabilitated with A. mangium and A. auriculiformis, and one was still dominated by Imperata cylindrica and Saccharum spontaneum. PN of A. mangium and A. auriculiformis showed significantly lower values than those of I. cylindrica and S. spontaneum. The Acacia plantations had more naturally regenerated tree species than the grassland. Additionally, more tree species appeared in the A. mangium plantation than in the A. auriculiformis plantation. Ficus spetica was present in all of the study sites. Dehydrogenase and phosphatase activities were significantly higher in soil under the Acacia plantations than under grassland. Grassland showed higher air temperature, relative humidity, and soil temperature as well as a larger variation per hour in these parameters compared to the Acacia plantations. The highest air temperature, relative humidity, and soil temperature were measured in April during the dry season. From the regression analysis, soil temperature was significantly correlated with air temperature. Hence plantations, as a rehabilitation activity for grassland, promote natural regeneration and stabilize the microclimate. This stabilization of the microclimate affects establishment and growth of naturally occurring tree species. and Y. K. Lee ... [et al.].
We conducted a hydroponic experiment in order to study effects of the ammonium/nitrate ratio (0:15, 5:10, 7.5:7.5, and 10:5) on photosynthetic characteristics and biomass accumulation in Brassica chinensis under low light intensity and water stress. Results showed that net photosynthetic rate, transpiration rate, intrinsic water-use efficiency, stomatal conductance, intercellular CO2 concentration, effective quantum yield of PSII photochemistry, electron transport rate, and nonphotochemical quenching were lower in the treatment (low light intensity and water deficit) than those in the control, whereas stomatal limitation increased. Minimum fluorescence, maximal quantum yield of PSII photochemistry, and photochemical quenching were largely unchanged. Pigment contents first increased and then decreased as the ammonium/nitrate ratios were altered, with significant differences between treatment and control observed at all ratios except for 10:5. Biomass first increased slightly and then decreased both in treated and control plants. Results suggest that economic losses caused by extreme conditions can be minimized by a proper adjustment of the ammonium/nitrate ratio., H. Q. Shang, G. M. Shen., and Obsahuje bibliografii
At a three-leaf stage, two Fe treatments [0 mg kg-1 (Fe-) and 20 mg.kg-1 (Fe+) in the form of FeCl3] were used in the soil of the pot and then two concentrations of α-ketoglutaric acid [0 mg L-1 (A-) and 50 mg L-1 (A+)] were sprayed to the rice plants of Meixiangzhan and Yuxiangyouzhan cultivars. We showed that seedlings exhibited an increased length and fresh and dry mass of shoots and roots with treatments Fe+A- and Fe-A+, as well as the Fe content increased greatly. Both treatments increased the morphological characteristic values of roots and promoted photosynthesis. Interestingly, Fe+A+ notably affected the photosynthesis of fragrant rice seedlings; however, it exerted no significant differences on other parameters. Overall, Fe and α-ketoglutaric acid had the potential for improving the growth of fragrant rice seedlings. The interaction between Fe and α-ketoglutaric acid regulated photosynthesis in seedling leaves, which provided evidence for further improvement of rice cultivation.
Energy transfer from resynthesized protochlorophyllide (PChlide) to chlorophyll (Chl) appeared after 5 h irradiation and additional redarkening of etiolated barley leaves. The transfer was more effective after a longer greening. Benzyladenine (BA) removed delay at the onset of the energy transfer and this process was effective even at very low Chl contents. BA enhanced Chl accumulation more strongly than the development of photosystems. The balance between the rate of Chl synthesis and that of its efflux from PChlide-containing site may determine the number of Chl molecules near PChlide, and thereby the probability of the energy transfer. At a high rate of Chl synthesis a part of its molecules remained near the PChlide synthesis site. Under various conditions of irradiation the slower rate of Chl accumulation corresponded to the more efficient energy transfer. Chl accumulation at PChlide forming site probably Controls the activity of the multienzyme systém of Chl biosynthesis by a feedback mechanism. The BA addition increased the number of EF-mtramembrane particles and the munber of enzyme systems of Chl biosynthesis to the same extent.