Variables of gas exchange of flag leaves and grain yield potentials of five representative winter wheat (Triticum aestivum L.) cultivars varied greatly across different development stages under the same management and irrigation. The cultivars with high yield potential had higher net photosynthetic rate (PN), PPFD (photosynthetic photon flux density) saturated photosynthetic rate (Psat), stomatal conductance (gs), and maximum apparent quantum yield of CO2 fixation (Φm,app) than those with low grain yield, but their dark respiration rate (RD) and compensation irradiance (Ic) were remarkably lower. Compared with overall increase of yield potential of 71 % from low yield cultivars to high yield ones, PN, Psat, Φm,app, and gs were 13, 19, 57, and 32 % higher, respectively; but RD and Ic decreased by 19 and 76 %, respectively. Such difference was evidently large during anthesis stage (e.g., PN by 33 %), which indicated that this period could be the best for assisting further selection for better cultivars. However, transpiration rate (E) and water use efficiency (WUE) differed only little. At different development stages, especially at anthesis, PN and Psat were positively correlated with Φm,app, gs, and yield potential, and negatively correlated with RD and Ic. Thus the high-yield-potential winter wheat cultivars possess many better characters in photosynthesis and associated parameters than the low-yield cultivars. and G. M. Jiang ... [et al.].
Diurnal variation of gas exchange, chlorophyll (Chl) fluorescence, and xanthophyll cycle components of three maize (Zea mays L.) hybrids released in different years, i.e. Baimaya (1950s), Zhongdan2 (1970s), and Nongda108 (1990s), were compared. On cloudless days, the newer hybrids always had higher net photosynthetic rate (PN), especially at noon, than the older ones. At noon, all the hybrids decreased their maximal yield of photosystem 2 (PS2) photochemistry (Fv/Fm) and actual quantum yield of PS2 (ΦPS2), the newer ones always showing higher values. Generally, the newer hybrids displayed higher photochemical quenching of Chl (qP) and lower non-photochemical quenching (NPQ). The interhybrid differences in PN may be owing to their differential photochemical efficiency. A midday depression in P N occurred in all hybrids, which might be caused by serious photoinhibition or by decreased stomatal conductance. However, midday depression in PN was more obvious in the older hybrids, especially when leaves were senescent. The higher de-epoxidation state of the xanthophylls was noted in older hybrids, which was confirmed by their larger NPQ. The newer maize hybrids did not need a strong de-epoxidation state since they had a better photosynthetic quantum conversion rate and a lower NPQ. and L. Ding ... [et al.].
The response of gas exchange and chlorophyll fluorescence along with changes in simulated rainfall were studied in water stressed plants Hedysarum fruticosum var. mongolicum (H.f.m.). Net photosynthetic rate (PN), stomatal conductance (gs), leaf water potential (Ψleaf), and apparent carboxylation efficiency (PN/Ci) were significantly increased with the increase of rainfall. However, they did not change synchronously. The complete recovery of both PN and PN/Ci appeared 3 d after watering while gs and Ψleaf were recovered 1 d after treatment. Gas exchange characters increased sharply from 5 to 15 mm rainfall and then maintained steady state with increasing rainfall. During the initial phase of water recovery, photosystem 2 (PS2) activity was not affected and its complete recovery occurred also 3 d after rainfall. Hence the recovery of PN was attributed to both opening of stomata and increase in carboxylation efficiency. Furthermore, PS2 activity was really impaired by water stress and could recover to the normal status when the water stress disappeared. and S. L. Niu ... [et al.].
Three winter wheat (Triticum aestivum L.) cultivars, representatives of those widely cultivated in Beijing over the past six decades, were grown in the same environmental conditions. Net photosynthetic rate (PN) per unit leaf area and instantaneous water use efficiency (WUE) of flag leaves increased with elevated CO2 concentration. With an increase in CO2 concentration from 360 to 720 µmol mol-1, PN and WUE of Jingdong 8 (released in 1990s and having the highest yield) increased by 173 and 81 %, while those of Nongda 139 (released in 1970s) increased by 88 and 66 %, and Yanda 1817 (released in 1945, with lowest yield) by 76 and 65 %. Jingdong 8 had the highest PN and WUE values under high CO2 concentration, but Yanda 1817 showed the lowest PN. Stomatal conductance (gs) of Nongda 139 and Yanda 1817 declined with increasing CO2 concentration, but gs of Jingdong 8 firstly went down and then up as the CO2 concentration further increased. Intercellular CO2 concentration (Ci) of Jingdong 8 and Nongda 139 increased when CO2 concentration elevated, while that of Yanda 139 increased at the first stage and then declined. Jingdong 8 had the lowest Ci of the three wheat cultivars, and Yanda 1817 had the highest Ci value under lower CO2 concentrations. However, Jingdong 8 had the highest PN and lowest Ci at the highest CO2 concentration which indicates that its photosynthetic potential may be high. and H. Q. Liu ... [et al.].
Gas exchange, photochemical efficiency, and leaf water potential (Ψl) of Salix matsudana (non-indigenous species), S. microstachya and S. gordejevii (indigenous species) were studied in Hunshandak Sandland, China. Ψl of all the three species decreased from 06:00 to 12:00, and increased afterwards. S. matsudana showed higher values of Ψl than others. Net photosynthetic rate (PN) and stomatal conductance (gs) of S. matsudana were the lowest among all, with the maximum PN at 10:00 being 75% of that of S. gordejevii. Compared with the indigenous species, the non-indigenous S. matsudana had also lower transpiration rate (E) and water use efficiency (WUE). The values of Fv/Fm in all the species were lower from 06:00 to 14:00 than those after 14:00, indicating an obvious depression in photochemical efficiency of photosystem 2 in both non-indigenous and native species. However, it was much more depressed in S. matsudana, the non-indigenous tree. PN was positively correlated to gs and negatively related to Ψl. The relationship between gs and vapour pressure difference (VPD) was exponential, while negative linear correlation was found between gs and Ψl. and M. Z. Liu ... [et al.].
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.].