Goldspur apple (Malus pumila cv. Goldspur) is one of the main fruit trees planted in semiarid loess hilly areas. The photosynthetic efficiency in leaves of eight-year-old trees were studied under different soil water conditions with a Li-6400 portable photosynthesis system and a Li-Cor1600 portable steady state porometer in order to explore the effects of soil water stress on photosynthesis and the suitable soil water content (SWC) for water-saving irrigation of apple orchards. The results showed that the leaf net photosynthetic rate (P N), transpiration rate (E), water-use efficiency (WUE), stomatal conductance (gs), intercellular CO2 concentration (Ci), and stomatal limiting value (Ls) displayed different threshold responses to soil water variation. When SWC was within a range of about 60%-86% of field capacity (FC), PN and E were maintained in a relative steady state. At an elevated level but below 60% of FC, both PN and E decreased evidently with decreasing soil moisture. The SWC needed to support WUE in a relatively steady state and at a high level was in the range of about 50%-71% of FC. When SWC was less than 48% of FC, g s and Ls declined with decreasing soil moisture, while Ci increased rapidly. Based on the analysis of the stomatal limitation of photosynthesis using two criteria (Ci and Ls) suggested by Farquhar and Sharkey, it was implied that the predominant cause of restricting PN had changed from stomatal limitation to nonstomatal one under severe water stress. In terms of water-saving irrigation for enhancing water-use efficiency, it was concluded that in semiarid loess hilly areas, the suitable range of SWC for water-saving irrigation in goldspur apple orchards is in the range of about 50%-71% of FC, and the most severe degree of soil water stress tolerated for photosynthesis is about 48% of FC. and S. Y. Zhang ... [et al.].
To investigate damaging mechanisms of chilling and salt stress to peanut (Arachis hypogaea L.) leaves, LuHua 14 was used in the present work upon exposure to chilling temperature (4°C) accompanied by high irradiance (1,200 μmol m-2 s-1) (CH), salt stress accompanied by high irradiance (1,200 μmol m-2 s-1) (SH), and high-irradiance stress (1,200 μmol m-2 s-1) at room temperature (25°C) (NH), respectively. Additionally, plants under low irradiance (100 μmol m-2 s-1) at room temperature (25°C) were used as control plants (CK). Relative to CK and NH treatments, both the maximal photochemical efficiency of PSII (Fv/Fm) and the absorbance at 820 nm decreased greatly in peanut leaves under CH and SH stress, which indicated that severe photoinhibition occurred in peanut leaves under such conditions. Initial fluorescence (F0), 1 - qP and nonphotochemical quenching (NPQ) in peanut leaves significantly increased under CH- and SH stress. Additionally, the activity of superoxide dismutase (SOD), one of the key enzymes of water-water cycle, decreased greatly, the accumulation of malondialdehyde (MDA) and membrane permeability increased. These results suggested that damages to peanut photosystems might be related to the accumulation of reactive oxygen species (ROS) induced by excess energy, and the water-water cycle could not dissipate energy efficiently under the stress of CH and SH, which caused the accumulation of ROS greatly. CH and SH had similar damaging effects on peanut photosystems, except that CH has more severe effects. All the results showed that CH- and SH stress has similar damaging site and mechanisms in peanut leaves. and L.-Q. Qin ... [et al.].
The effects of experimental warming on the growth and physiology of grass Elymus nutans and forb Potentilla anserina were studied by using open-top chambers (OTCs) in an alpine meadow of the eastern Tibetan Plateau. The warming treatment increased mean air and soil surface temperatures by 1.53°C and 0.50°C, respectively, but it reduced soil relative water content in the surface layer. Experimental warming enhanced the growth and gas exchange of E. nutans, while it reduced those of P. anserina. Experimental warming resulted in an increased efficiency of photosystem II (PSII) in E. nutans, while decreasing it in P. anserina; significantly stimulated non-photochemical quenching, antioxidative enzymes and non-enzymes in both species; and significantly reduced malondialdehyde content in E. nutans, while promoting it in P. anserina. The results of this study indicated that the two species showed different growth responses to experimental warming and their different physiological performances further indicated that experimental warming alleviated the negative effect of low temperature on the growth and development of E. nutans, but limited the competitive ability of P. anserina in the study region. and F. S. Shi ... [et al.].
The impact of grazing by domestic goats, Capra hircus, on the photochemical apparatus of three co-ocurring Mediterranean shrubs, Erica scoparia, Halimium halimifolium, and Myrtus communis was evaluated. Seasonal course of gas exchange, chlorophyll fluorescence and photosynthetic pigment concentrations were measured in the field in grazed and ungrazed plants. Net photosynthetic rate was higher in grazed plants of E. scoparia and H. halimifolium in May, while there were not significant differences in M. communis. Photosynthetic enhancement in grazed plants of E. scoparia could be explained largely by higher stomatal conductance. On the other hand, the lack of differences in stomatal conductance between grazed and ungrazed plants of
H. halimifolium could indicate that carboxylation efficiency, and ribulose-1,5-bisphosphate (RuBP) regeneration may have been enhanced by grazing. Overall grazing has little effect on the photochemical (PSII) apparatus, however grazed plants of M. communis showed chronic photoinhibition in the short term. Finally, seasonal variations recorded on photosynthesis, photochemical efficiency and pigment concentrations may be a physiological consequence of environmental factors, such as summer drought and competition for light, rather than an adaptation to grazing. and S. Redondo-Gómez ... [et al.].
Leaf stomatal conductance (gs), transpiration rate (E), and light-saturated net photosynthetic rate (PNmax) at three developmental stages (tillering stage, jointing-booting stage, and milking stage) and leaf total nitrogen concentration (LTNC) and δ13C value at milking stage were measured for a conventional rice line (Minghui 63) and its corresponding Bacillus thuringiensis (Bt)-gene [cry1A
(b and c)] introduced line (Bt line) under three fertilizer levels. Compared to conventional line, Bt line showed lower gs, which was associated with lower P Nmax and E, but instantaneous water-use efficiency (WUE), measured as the ratio of PNmax to E, was higher in the Bt line than in the conventional line, particularly in the jointing-booting stage. However, δ13C values were not significantly different across treatments, suggesting that intrinsic water-use efficiency (WUEin) might be indistinguishable between Bt and conventional lines. LTNC was higher but PNmax was lower in Bt line compared to conventional line, resulting in significantly lower photosynthetic nitrogen-use efficiency (PNUE). This might result from the additional cost of producing Bt protein in the Bt line due to the effect of competing nitrogen with photosynthetic machinery. Bt-gene introduction and expression does not significantly change WUEin but may significantly decrease leaf PNUE. Thus we suggest that Bt rice should be carefully examined in relation to environmental risks (e.g. water-body pollution) before planting commercially. and R. Q. Guo ... [et al.].
In eukaryotic oxygenic photosynthetic organisms (both plants and algae), the maximum fluorescence is at peak P, with peak M lying much lower, or being even absent. Thus, the PSMT phase, where S is semisteady state, and T is terminal state, is replaced by a monotonous P→T fluorescence decay. In the present study, we found that dimethoate-treated wheat plant leaves showed SM transient, whereas in the case of control plants monotonous P→T fluorescence decay occured. We suggest that this was partly due to quenching of fluorescence due to [H+], responsible for P to S (T) decay in control plants (Briantais et al. 1979) being replaced by state transition (state 2 to state 1) in dimethoate-treated plants (Kaňa et al. 2012)., J. K. Pandey, R. Gopal., and Obsahuje bibliografii
The Amazonian peach palm (Bactris gasipaes Kunth) has been grown for heart-of-palm production under subtropical conditions. As we did not see any substantial study on its photosynthesis under Amazonian or subtropical conditions, we carried out an investigation on the diurnal and seasonal variations in photosynthesis of peach palms until the first heart-of-palm harvest, considering their relationship with key environmental factors. Spineless peach palms were grown in 80-L plastic pots, under irrigation. Gas exchange and chlorophyll fluorescence emission measurements were taken in late winter, mid spring, mid summer and early autumn, from 7:00 to 18:00 h, with an additional chlorophyll fluorescence measurement at 6:00 h. The highest net CO2 assimilation (PN), observed in mid summer, reached about 15 μmol m-2 s-1, which was about 20% higher than the maximum values found in autumn and spring, and 60% higher than that in winter The same pattern of diurnal course for PN was observed in all seasons, showing higher values from 8:00 to 9:00 h and declining gradually from 11:00 h toward late afternoon. The diurnal course of stomatal conductance (gs) followed the same pattern of
PN, with the highest value of 0.6 mol m-2 s-1 being observed in February and the lowest one (0.23 mol m-2 s-1) in September. The maximal quantum yield of photosystem II (Fv/Fm) was above 0.75 in the early morning in all the months. The reversible decrease was observed around midday in September and October, suggesting the occurrence of dynamic photoinhibition. A significant negative correlation between the leaf-air vapour pressure difference (VPDleaf-air) and PN and a positive correlation between PN and gs were observed. The photosynthesis of peach palm was likely modulated mainly by the stomatal control that was quite sensible to atmospheric environmental conditions. Under subtropical conditions, air temperature (Tair) and VPDleaf-air impose more significant effects over PN of peach palm than an excessive photosynthetic photon flux density (PPFD). The occurrence of dynamic photoinhibition indicates that under irrigation, peach palms appeared to be acclimated to the full-sunlight conditions under which they have been grown. and M. L. S. Tucci ... [et al.].
Diurnal dynamics of photosynthetic character of Angelica sinensis, as well as effect of continuous cropping on leaf photosynthetic character, antioxidant enzyme activity and growth of A. sinensis were investigated under field condition. The results showed that the diurnal net photosynthetic rate of A. sinensis in sunny day exhibited a double-peak pattern, and the peaks occurred at 9:45 and 16:45 h, respectively. There was a significant midday depression with A. sinensis, which was caused principally by stomatal factors such as stomatal conductance. The results also showed that net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), intercellular CO2 concentration (Ci), and chlorophyll content (Chl) of A. sinensis plants under continuous cropping were significantly lower than those of the control. The activity of total superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and growth parameters of A. sinensis plants were significantly decreased under continuous cropping condition. This study provides evidence of continuous cropping obstacle effect on photosynthesis, antioxidant enzyme activity, and growth parameters of A. sinensis in a field experiment, which partly explained the yield reduction of A. sinensis in the field, when it was cultivated continuously on the same soil., X. H. Zhang ... [et al.]., and Obsahuje bibliografii
Z geobotanického hlediska je popsána subalpinská a alpinská vegetace v horách jihovýchodní Brazílie. Přirozené požáry tam ovlivňují strukturu rostlinných společenstev. Jsou zmíněny zajímavé životní způsoby, jako je mykorhiza, hemiparazitismus a masožravost. Jedním z nejzajímavějších fenomenů je symbióza mezi masožravou rostlinou Utricularia cornigera (bublinatkou růžkatou) a růžicovitými rostlinami Vriesea atra nebo Eryngium fluminense. Je diskutováno o problému srovnávání popsané brazilské vegetace a páramos v Andách. Pojem "brazilská páromos" je odmítnut., The subalpine and alpine vegetation in mountains of south-eastern Brazil is described from the botanical point of view. Natural fires affect the structure of plant communities there. Interesting life strategies, such as mycorrhiza, hemiparasitism and carnivory, are mentioned. One of the most interesting is the symbiosis between carnivorous Utricularia cornigera and rosette plants of Vriesea atra or Eryngium fluminense. Brazilian vegetation and páramos in the Andes are compared., and Miloslav Studnička.