72 to 120 h of soil flooding of barley plants (Hordeum vulgare L. cv. Alfa) led to a noticeable decrease in the rates of CO2 assimilation and transpiration, and in chlorophyll and dry mass contents. Stomatal conductance decreased following flooding without appreciable changes in the values of intercellular CO2 concentrations. A drop in the activity of ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) and of the photorespiratory enzymes phosphoglycollate phosphatase (EC 3.1.3.18) and glycollate oxidase (EC 1.1.3.1) was observed, while the activity of phosphoenolpyruvate carboxylase (EC 4.1.1.31) increased in all flooded plants. Flooding of barley plants caused an increase in proline content and in leaf acidity. and R. Y. Yordanova, L. P. Popova.
European beech (Fagus sylvatica L.) seedlings of three different origins were used to evaluate the effect of water deficit and recovery during the most vulnerable phase of forest tree life. Gas-exchange characteristics and fluorescence rapid light curves were studied in the seedlings from a warm region (PV1, 530 m a.s.l.), seedlings from a moderately warm region (PV2, 625 m a.s.l.), optimal for beech, and in seedlings from a cool region (PV3; 1,250 m a.s.l.). Changes in photosynthetic characteristics caused by water deficit were similar, but their intensity was dependent on the origin of the seedlings. Simulation of drought conditions by the interruption of watering led to a decrease in the efficiency of primary photochemistry in PSII, with the most significant decrease in the PV2 seedlings. Conversely, water deficit affected most significantly gas exchange in PV3, where the recovery process was also the worst. The PV1 demonstrated the highest resistance to water deficit. Drought-adaptation of beech seedlings at non-native sites seems to be linked to water availability and to the origin of the beech seedlings., E. Pšidová, Ľ. Ditmarová, G. Jamnická, D. Kurjak, J. Majerová, T. Czajkowski, A. Bolte., and Obsahuje bibliografii
Response to irradiance of leaf net photosynthetic rates (PN) of four carrot cultivars: Cascade, Caro Choice (CC), Oranza, and Red Core Chantenay (RCC) were examined in a controlled environment. Gas exchange measurements were conducted at photosynthetic active radiation (PAR) from 100 to 1 000 μmol m-2 s-1 at 20 °C and 350 μmol (CO2) mol-1(air). The values of PN were fitted to a rectangular hyperbolic nonlinear regression model. PN for all cultivars increased similarly with increasing PAR but Cascade and Oranza generally had higher PN than CC. None of the cultivars reached saturation at 1 000 μmol m-2 s-1. The predicted PN at saturation
(PNmax) for Cascade, CC, Oranza, and RCC were 19.78, 16.40, 19.79, and 18.11 μmol (CO2) m-2 s-1, respectively. The compensation irradiance (I c) occurred at 54 μmol m-2 s-1 for Cascade, 36 μmol m-2 s-1 for CC, 45 μmol m-2 s-1 for Oranza, and 25 μmol m-2 s-1 for RCC. The quantum yield among the cultivars ranged between 0.057-0.033 mol(CO2) mol-1(PAR) and did not differ. Dark respiration varied from 2.66 μmol m-2 s-1 for Cascade to 0.85 μmol m-2 s-1 for RCC. As PN increased with PAR, intercellular CO2 decreased in a non-linear manner. Increasing PAR increased stomatal conductance and transpiration rate to a peak between 600 and 800 μmol m-2 s-1 followed by a steep decline resulting in sharp increases in water use efficiency. and S. Kyei-Boahen ... [et al.].
Surface sterilised seeds of mungbean (Vigna radiata L. Wilczek cv. T-44) were soaked in 0, 10-8, 10-6, or 10-4 M aqueous solution of 28-homobrassinolide (HBR) for 4, 8, or 12 h. The treated seeds were grown in sandy loam soil filled in earthen pots and sampled at 30, 40, and 50 d. Net photosynthetic rate, leaf chlorophyll content, carbonic anhydrase activity (E.C. 4.2.1.1), carboxylation efficiency, stomatal conductance, and seed yield at harvest were enhanced by the HBR treatment. The best combination was the pre-sowing seed treatment with 10-6 M HBR for 8 h. and Q. Fariduddin, A. Ahmad, S. Hayat.
Net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), and leaf water potential (Ψl) of an annual pioneer C4 grass (Agriophyllum squarrosum) were compared under different simulated precipitation events in a field of Hunshandak Sandland, China. The increase of soil water content (SWC) had significant effect on these physiological traits (p<0.001). In the vegetative stage, the values of PN, E, and gs went up sharply when SWC increased at the beginning, while they went down with continuous increase of SWC. PN, E, and gs increased 1.4, 1.7, and 1.7 fold, respectively, with SWC range from 6.7 to 11.6 %. In the reproductive stage, similar trends were found, except for the climate with a higher SWC. This indicated that A. squarrosum was very sensitive to the small increment of SWC which might have a large photosynthetic potential. Ψl increased by about 8 % as the SWC changed from 6.7 to 8.8 %, and then maintained a steady level when the SWC was higher than 8.8 %, while the values of PN, E, and gs kept increasing even after this SWC. This might indicate that the adjustment of Ψl response to the changes of SWC lagged that of the photosynthetic parameters. and M. Z. Liu ... [et al.].
Two cultivars (Katy and Erhuacao) of apricot (Prunus armeniaca L.) were evaluated under open-field and solar-heated greenhouse conditions in northwest China, to determine the effect of photosynthetic photon flux density (PPFD), leaf temperature, and CO2 concentration on the net photosynthetic rate (PN). In greenhouse, Katy registered 28.3 µmol m-2 s-1 for compensation irradiance and 823 µmol m-2 s-1 for saturation irradiance, which were 73 and 117 % of those required by Erhuacao, respectively. The optimum temperatures for cvs. Katy and Erhuacao were 25 and 35 °C in open-field and 22 and 30 °C in greenhouse, respectively. At optimal temperatures, PN of the field-grown Katy was 16.5 µmol m-2 s-1, 21 % less than for a greenhouse-grown apricot. Both cultivars responded positively to CO2 concentrations below the CO2 saturation concentration, whereas Katy exhibited greater PN (18 %) and higher carboxylation efficiency (91 %) than Erhuacao at optimal CO2 concentration. Both cultivars exhibited greater photosynthesis in solar-heated greenhouses than in open-field, but Katy performed better than Erhuacao under greenhouse conditions. and F. L. Wang, H. Wang, G. Wang.
The effects of shade on the gas exchange of four Hosta cultivars were determined under differing irradiances (5, 30, 50, and 100 % of full irradiance) within pots. Irradiance saturation ranged between 400-800 μmol m-2 s-1 among the four cultivars, of which H. sieboldiana cv. Elegans and H. plantagenea cv. Aphrodite exerted the lowest saturation and compensation irradiances. The maximal photosynthetic rate (Pmax) was significantly higher in shade than in full irradiance in Elegans and Aphrodite, and was at maximum in seedlings grown in 30 % of full irradiance. The best shade treatment for cvs. Antioch and Golden Edger was 50 % of full irradiance. The diurnal gas exchange patterns in four cultivars were greatly influenced by the irradiance. Single-peak patterns of net photosynthetic rate (PN) and stomatal conductance (gs) were observed under 5 and 30 % full irradiance for all the cultivars while Elegans and Aphrodite suffered from midday depression in 50 % of full irradiance. Under open sky, all four cultivars showed two-peak patters in their diurnal gas exchange, but the midday depression was less in Antioch and Golden Edger than in Elegans and Aphrodite. According to their photosynthetic responses to shade, the shade tolerance of the four cultivars was in the order: Elegans>Aphrodite>Antioch>Golden Edger. and J. Z. Zhang ... [et al.].
Saplings of the tropical trees Tibouchina pulchra (Cham.) Cogn., Caesalpinia echinata Lam., and Psidium guajava L. cv. Paluma were exposed in open-top chambers with charcoal filtered air and measurements of gas exchange and chlorophyll fluorescence were made before (t1) and after exposure to non-filtered air plus O3 (t2), simulating 6-h peaks of O3 similar to those observed in São Paulo city (SE Brazil, reaching an AOT40 of 641 nmol mol-1). After the fumigation, the net photosynthetic rate, stomatal conductance, transpiration rate, and Fv/Fm were reduced (p<0.05) for the three species. C. echinata was the most sensitive species and P. guajava cv. Paluma the most resistant. and R. M. Moraes ... [et al.].
Net photosynthetic rate (PN) was high in genotypes with 'C' genome both in the nucleus and cytoplasm. This may be attributed to the co-ordinated manner of acting of both genome sources. Leaf mass per area (LMA) and chlorophyll content increased with leaf nitrogen (N) content but did not show any correlation with PN. The factors which affected PN had the same effect on photosynthetic nitrogen use efficiency (pNUE). Thus, differential allocation of N to the various components influences plant pNUE which is not significantly affected by genome constitution. and A. Anand, K. Suresh, T. V. R. Nair.
We found differences between true leaves (TL) and phyllodes (Ph) during ontogeny of Acacia mangium plants as reflected in chlorophyll (Chl) and carotenoid contents, gas exchange, Chl fluorescence, and growth. The production of TL enhanced the relative growth rate of the A. mangium seedlings, allowing the plants to accumulate enough dry biomass for later growth, while the production of thicker Ph in the later growth stage of A. mangium could help plants to cope with higher irradiance in their natural growth conditions. and H. Yu, J.-T. Li.