We compared the effects of salt-stresses (SS, 1: 1 molar ratio of NaCl to Na2SO4) and alkali-stresses (AS, 1: 1 molar ratio of NaHCO3 to Na2CO3) on the growth, photosynthesis, solute accumulation, and ion balance of barley seedlings, to elucidate the mechanism of AS (high-pH) damage to plants and the physiological adaptive mechanism of plants to AS. The effects of SS on the water content, root system activity, membrane permeability, and the content of photosynthetic pigments were much less than those of AS. However, AS damaged root function, photosynthetic pigments, and the membrane system, led to the severe reductions in water content, root system activity, content of photosynthetic pigments, and net photosynthetic rate, and a sharp increase in electrolyte leakage rate. Moreover, with salinity higher than 60 mM, Na+ content increased slowly under SS and sharply under AS. This indicates that high-pH caused by AS might interfere with control of Na+ uptake in roots and increase intracellular Na+ to a toxic level, which may be the main cause of some damage emerging under higher AS. Under SS, barley accumulated organic acids, Cl-, SO4 2-, and NO3 - to balance the massive influx of cations, the contribution of inorganic ions to ion balance was greater than that of organic acids. However, AS might inhibit absorptions of NO3 - and Cl-, enhance organic acid synthesis, and SO4 2- absorption to maintain intracellular ion balance and stable pH. and C.-W. Wang ... [et al.].
The seedlings of wheat were treated by salt-stress (SS, molar ratio of NaCl: Na2SO4 = 1:1) and alkali-stress (AS, molar ratio of NaHCO3: Na2CO3 = 1:1). Relative growth rate (RGR), leaf area, and water content decreased with increasing salinity, and the extents of the reduction under AS were greater than those under SS. The contents of photosynthetic pigments did not decrease under SS, but increased at low salinity. On the contrary, the contents of photosynthetic pigments decreased sharply under AS with increasing salinity. Under SS, the changes of net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were similar and all varied in a single-peak curve with increasing salinity, and they were lower than those of control only at salinity over 150 mM. Under AS, PN, gs, and E decreased sharply with rising salinity. The decrease of gs might cause the obvious decreases of E and intercellular CO2 concentration, and the increase of water use efficiency under both stresses. The Na+ content and Na+/K+ ratio in shoot increased and the K+ content in shoot decreased under both stresses, and the changing extents under AS were greater than those under SS. Thus SS and AS are two distinctive stresses with different characters; the destructive effects of AS on the growth and photosynthesis of wheat are more severe than those under SS. High pH is the key feature of the AS that is different from SS. The buffer capacity is essentially the measure of high pH action on plant. The deposition of mineral elements and the intracellular unbalance of Na+ and K+ caused by the high pH at AS might be the reason of the decrease of PN and gs and of the destruction of photosynthetic pigments. and C. W. Yang ... [et al.].
Seedlings of Chloris virgata were treated with varying (0-160 mM) salt-stress (SS; 1 : 1 molar ratio of NaCl to Na2SO4) or alkali-stress (AS; 1 : 1 molar ratio of NaHCO3 to Na2CO3). To compare these effects, relative growth rates (RGR), stored energy, photosynthetic pigment contents, net photosynthetic rates, stomatal conductance, and transpiration rates were determined. Both stresses did not change significantly the photosynthetic parameters of C. virgata under moderate stress (below 120 mM). Photosynthetic ability decreased significantly only at high stress (160 mM). Thus C. virgata, a natural alkali-resistant halophyte, adapts better to both kinds of stress. The inhibition effects of AS on RGR and energy storage of C. virgata were significantly greater than that of SS of the same intensity. The energy consumption of C. virgata was considerably greater while resisting AS than while resisting SS. and C. W. Yang ... [et al.]
We determined the interactive effects of irradiance, elevated CO2 concentration (EC), and temperature in carrot (Daucus carota var. sativus). Plants of the cv. Red Core Chantenay (RCC) were grown in a controlled environmental plant growth room and exposed to 3 levels of photosynthetically active radiation (PAR) (400, 800, 1 200 µmol m-2 s-1), 3 leaf chamber temperatures (15, 20, 30 °C), and 2 external CO2 concentrations (Ca), AC and EC (350 and 750 µmol mol-1, respectively). Rates of net photosynthesis (PN) and transpiration (E) and stomatal conductance (gs) were measured, along with water use efficiency (WUE) and ratio of internal and external CO2 concentrations (Ci/Ca). PN revealed an interactive effect between PAR and Ca. As PAR increased so did PN under both C a regimes. The gs showed no interactive effects between the three parameters but had singular effects of temperature and PAR. E was strongly influenced by the combination of PAR and temperature. WUE was interactively affected by all three parameters. Maximum WUE occurred at 15 °C and 1 200 µmol m-2 s-1 PAR under EC. The Ci /Ca was influenced independently by temperature and Ca. Hence photosynthetic responses are interactively affected by changes in irradiance, external CO2 concentration, and temperature. EC significantly compensates the inhibitory effects of high temperature and irradiance on PN and WUE. and A. Thiagarajan, R. Lada, P. Joy.
Diurnal and seasonal changes in photosynthetic characteristics, leaf area dry mass (ADM), and reducing sugar and total chlorophyll (Chl) contents of leaves of Frantoio, Leccino, and Maurino olive cultivars were investigated in Central Italy. Leaf net photosynthetic rate (PN) per unit leaf area changed during the growing season and during the day, but the cultivar did not significantly influence the changes. In both young and one-year-old leaves the highest PN values were observed in October, while the lowest values were recorded in August and December; during the day the highest PN values were generally found in the morning. The pattern of photosynthetic response to photosynthetic photon flux density (PPFD) of leaves was similar in the three genotypes. Sub-stomatal CO2 concentration (CI) tended to increase when PN decreased. The increase in CI was accompanied by a stomatal conductance to water vapor (gS) decrease. In general, PN and dark respiration rate (RD) were correlated. Transpiration rate (E), with no differences between the cultivars, increased from April to July, decreased greatly in August, then increased in October and finally decreased again in December. Leaf water content increased from April to June, remained high until mid July, decreased significantly in August, remaining constant until December with no differences associated with the cultivar. In both young and one-year-old leaves, the leaf water content per unit leaf area was slightly greater in Frantoio than in the other two cultivars. The one-year-old leaves had a higher Chl content than the young ones. The cultivar did not substantially influence the leaf reducing sugar content which decreased from April to August, when it reached the lowest level, then increased rapidly until October. During the day the reducing sugar content did not change significantly. The leaf ADM was slightly higher in Frantoio than in the other cultivars and one-year-old leaves had higher values than the young ones. Leaf ADM decreased from April to June and then tended to increase until December. During the day there were no substantial variations. and P. Proietti, F. Famiani.
Diurnal and seasonal trends in net photosynthetic rate (PN), stomatal conductance (g), transpiration rate (E), vapour pressure deficit, temperature, photosynthetic photon flux density, and water use efficiency (WUE) were compared in a two-year-old Dalbergia sissoo and Hardwickia binata plantation. Mean daily maximum PN in D. sissoo ranged from 21.40±2.60 µmol m-2 s-1 in rainy season I to 13.21±2.64 µmol m-2 s-1 in summer whereas in H. binata it was 20.04±1.20 µmol m-2 s-1 in summer and 13.64±0.16 µmol m-2 s-1 in winter. There was a linear relationship between daily maximum PN and gs in D. sissoo but there was no strong linear relationship between PN and gs in H. binata. In D. sissoo, the reduction in gs led to a reduction in both PN and E enabling the maintenance of WUE during dry season thereby managing unfavourable environmental conditions efficiently whereas in H. binata, an increase in gs causes an increase of PN and E with a significant moderate WUE. and S. G. Saraswathi, K. Paliwal.
Net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), leaf water potential (ψleaf), leaf nitrogen content, and photosynthetic nitrogen use efficiency (PNUE) were compared between a typical C4 plant, Agriophyllum squarrosum and a C3 plant, Leymus chinensis, in Hunshandak Sandland, China. The plant species showed different diurnal gas exchange patterns on June 12-14 when photosynthetic photon flux density (PPFD), air temperature (Tair), and water potential were moderate. PN, E, and
gs of A. squarrosum showed distinct single peak while those of L. chinensis were depressed at noon and had two peaks in their diurnal courses. Gas exchange traits of both species showed midday depression under higher photosynthetic photon flux density (PPFD) and T air when Ψleaf was significantly low down on August 6-8. However, those of A. squarrosum were depressed less seriously. Moreover, A. squarrosum had higher PN, Ψleaf, water use efficiency (WUE), and PNUE than L. chinensis. Thus A. squarrosum was much more tolerant to heat and high irradiance and could utilise the resources on sand area more efficiently than L. chinensis. Hence species like A. squarrosum may be introduced and protected to reconstruct the degraded sand dunes because of their higher tolerance to stress and higher resource use efficiency. and S. L. Niu ... [et al.].
The aim of the study was to the assess the influence of Ca/Mg ions ratio on the photosynthetic activity of Salix viminalis L. ‘Cannabina’ plants cultivated in medium enriched with Cu(NO3)2. The experiment was conducted in controlled conditions in a phytotron for 21 days; hence the early plant response was tested. Plants were cultivated with different Ca/Mg ions ratios, i.e. (4:1)l, (4:1)h, and 1:10. Plants were additionally treated with Cu(NO3)2 at 1, 2, and 3 mM concentration in cultivation medium. Net photosynthetic rate, stomatal conductance and transpiration were measured after the first, second and third week of cultivation. Additionally, chlorophyll content, leaf morphology, root biomass and copper accumulation in leaves and roots were investigated. The investigations revealed differences in plant response to particular treatments - differences in Cu accumulation for particular Ca/Mg ions ratios were detected. It seems that plants are adapted to high Cu2+ concentrations, when 1:10 Ca/Mg ions ratio is applied. The highest Cu accumulation in roots was noted for plants fertilized with 1:10 Ca/Mg ions ratio, together with high Cu translocation to above-ground plant organs, which suggests its higher potential in phytoremediation., K. Borowiak ... [et al.]., and Obsahuje bibliografii
Growth, photosynthetic gas exchange, and chlorophyll fluorescence characteristics were investigated in wild type (WT) and Cd-sensitive mutant rice (Oryza sativa L.) plants using 50 µM Cd treatment for 12 d followed by a 3-d recovery. Under Cd stress, net dry mass and pigment contents were significantly lower in the mutant plants than in the WT. The mutant had lower net photosynthetic rate (P N), transpiration rate (E), and stomatal conductance (g s) than WT rice, however, it had higher intercellular CO2 concentration (C i), indicating that non-stomatal factors accounted for the inhibition of P N. Maximal photochemical efficiency of photosystem 2 (Fv/Fm), effective quantum yield of PS2 (ΦPS2), and photochemical quenching (qP) decreased much in the mutant under Cd stress. Cd content in roots and leaves of the mutant was significantly higher than those in the WT. Hence Cd toxicity was associated with the marked increases in Cd contents of plant tissue. After the recovery for 3 d, the WT rice had higher capacity to recover from Cd injury than the mutant. and J.-Y. He ... [et al.].
On the first day after foliar application, chitosan pentamer (CH5) and chitin pentamer (CHIT5) decreased net photosynthetic rate (PN) of soybean and maize, however, on subsequent days there was an increase in PN in some treatments. CH5 caused an increase in maize PN on day 3 at 10-5 and 10-7 M; the increases were 18 and 10 % over the control plants. This increase was correlated with increases in stomatal conductance (gs) and transpiration rate (E), while the intercellular CO2 concentration (Ci) was not different from the control plants. PN of soybean plants did not differ from the control plants except for treatment CH5 (10-7 M) which caused an 8 % increase on day 2, along with increased gs, E, and Ci. On days 5 and 6 the CHIT5 treatment caused a 6-8 % increase in PN of maize, which was accompanied by increases in gs, E, and Ci. However, there was no such increase for soybean plants treated with CHIT5. In general, foliar application of high molecular mass chitin (CHH) resulted in decreased PN, particularly for 0.010 % treated plants, both in maize and soybean. Foliar applications of chitosan and chitin oligomers did not affect (p > 0.05) maize or soybean height, root length, leaf area, shoot or root or total dry mass. and W. M. Khan, B. Prithiviraj, D. L. Smith.