Anastatica hierochuntica is an annual desert plant, which was recently shown to have unusually low nonphotochemical quenching (NPQ) and a high PSII electron transport rate (ETR). In the current study, we examined how these unusual characteristics are related to a lack of CO2 and inhibition of net photosynthetic rate (P N). We compared the photosynthetic and photoprotective response of A. hierochuntica and sunflower (Helianthus annuus), under conditions of photosynthetic inhibition, with either low CO2 or drought. We found that under nonsteady state conditions of low CO2 availability, A. hierochuntica exhibited about half of the NPQ values and almost twice of the ETR values of H. annuus. However, the long-term inhibition of P N under drought caused a similar increase in NPQ and a decrease in ETR in both A. hierochuntica and H. annuus. These results suggest that the unusually low NPQ and high ETR in A. hierochuntica are not directly related to a response to drought conditions., A. Eppel, S. Rachmilevitch., and Obsahuje seznam literatury
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
Small rainfall events (≤ 5 mm) have short intervals, but account for a large proportion of the annual rainfall frequency in arid lands. To explore possible strategies used by desert plants to utilize the small rainfall events, we investigated the photosynthetic responses of 28 species to 1 mm and 6 mm of simulated rainfall in the Junggar Basin, northwest China. The species were grouped into four plant functional types: short-life-cycle herbs, long-life-cycle herbs, non-phreatophyte shrubs, and phreatophyte shrubs. The results showed that the net photosynthetic rate, stomatal conductance, and transpiration rate increased in most of the herbs, but they responded differently to the rainfall treatments. However, the water-use efficiency did not significantly differ after 1 and 6 mm rainfall treatments in most of the shrubs. The maximum water absorption by leaves and the percentage increase of a leaf water content (LWC) were higher in the herbs than those in the shrubs. Plants with dense trichomes had the highest LWC. The results suggested that the desert plants benefited from the
micro-environment humidity provided by the small rainfall events., Y. Wu, X. J. Zheng , Y. Li., and Obsahuje seznam literatury
In the field, supplemental application of N fertilizer to rice (Oryza sativa) shortly before the beginning of heading stage increases leaf N content and enhances photosynthesis during the grain-filling period. In search of varietal differences in leaf gas exchange in response to supplemental N application, we examined 13 rice varieties grown in the field during two successive years. The varieties included japonica and indica varieties, both of which are widely grown in Japan. The response to supplemental N application could not be separated clearly between variety groups; some of the japonica varieties, but none of the indica varieties, exhibited significant increase in stomatal conductance (gs) after supplemental N application. Supplemental N was more effective to increase stomatal aperture in the varieties with inherently lower gs. Varieties that showed greater response of g s to supplemental N application might be able to adjust their stomatal aperture with appropriate N control. Although the internal-to-ambient CO2 mole fraction ratio and the leaf carbon isotopic composition (δ13C) differed among varieties as a result of variations in stomatal aperture and the CO2 requirement of mesophyll, supplemental N application barely influenced these parameters, because it only moderately affected stomatal aperture. Since δ13C tended to increase with increasing number of days from transplantation to heading stage in japonica varieties, δ13C values were more sensitive to differences in growth rate between years than to N application., S. Shimoda, A. Maruyama., and Obsahuje bibliografii
Cuttings of Populus cathayana were exposed to three different alkaline regimes (0, 75, and 150 mM Na2CO3) in a semicontrolled environment. The net photosynthesis rate (PN), mesophyll conductance (gm), the relative limitations posed by stomatal conductance (Ls) and by mesophyll conductance (Lm), photosynthetic nitrogen-use efficiency (PNUE), carbon isotope composition (δ13C), as well as specific leaf area (SLA) were measured. PN decreased due to alkaline stress by an average of 25% and gm decreased by an average of 57%. Alkaline stress caused an increase of Lm but not Ls, with average Ls of 26%, and Lm average of 38% under stress conditions. Our results suggested reduced assimilation rate under alkaline stress through decreased mesophyll conductance in P. cathayana. Moreover, alkaline stress increased significantly δ13C and it drew down CO2 concentration from the substomatal cavities to the sites of carboxylation (Ci-Cc), but decreased PNUE. Furthermore, a relationship was found between PNUE and Ci-Cc. Meanwhile, no correlation was found between δ13C and Ci/Ca, but a strong correlation was proved between δ13C and Cc/Ca, indicating that mesophyll conductance was also influencing the 13C/12C ratio of leaf under alkaline stress. and G. Xu ... [et al.].
Variations in leaf gas-exchange characteristics, leaf pigment content, and other important leaf traits were investigated in seven wild Oryza species, five hybrids, and five improved varieties. The significant variations were observed in photosynthetic pigment contents amongst different species of Oryza. The mean chlorophyll (Chl) content was higher in O. sativa (varieties and hybrids), while O. eichengeri showed the lowest Chl content. The mean carotenoid (Car) content in O. sativa (varieties and hybrids) was higher than in other wild rice species. O. eichengeri and O. barthii had significantly lower Car contents than other rice species. Significant differences were noticed in the rate of photosynthesis (PN), stomatal conductance (gs), transpiration rate (E), internal CO2 concentration (Ci), specific leaf mass (SLM), and leaf thickness amongst different Oryza species. The mean PN was the highest in O. nivara followed by O. eichengeri. The mean PN was the lowest in O. glumaepatula, which was lower than that of cultivated varieties and hybrids of O. sativa. High rates of photosynthesis were observed in O. nivara (ACC. No. CR 100097), O. rufipogon (ACC.No. CR 100267), and O. nivara (ACC.No. CR 100008). The O. nivara and O. rufipogon genotypes with high PN might be used in rice improvement programmes for an increase of leaf photosynthesis in rice. Multiple correlations performed between different gas-exchange characteristics and other physiological traits revealed that the rate of photosynthesis was not dependent on the leaf pigment content or the leaf thickness. A strong positive correlation between PN and the PN/Ci ratio, which represents the carboxylation efficiency, indicated that the observed variation in PN was not based on pigment content or other leaf traits. and T. V. Kiran ... [et al.].