Net photosynthetic rate (PN), transpiration rate (E), water use efficiency (WUE), stomatal conductance (gs), and stomatal limitation (Ls) were investigated in two Syringa species. The saturation irradiance (SI) was 400 µmol m-2s-1 for S. pinnatifolia and 1 700 µmol m-2s-1 for S. oblata. Compared with S. oblata, S. pinnatifolia had extremely low gs. Unlike S. oblata, the maximal photosynthetic rate (Pmax) in S. pinnatifoliaoccurred around 08:00 and then fell down, indicating this species was sensitive to higher temperature and high photosynthetic photon flux density. However, such phenomenon was interrupted by the leaf development rhythms before summer. A relatively lower PN together with a lower leaf area and shoot growth showed the capacity for carbon assimilation was poorer in S. pinnatifolia. and H. X. Cui ... [et al.].
The genetic basis of stomatal conductance (gs), net photosynthetic rate (PN), and transpiration rate (E) was explored by using a wheat doubled haploid population from a cross of Hanxuan10 and Lumai 14. The above three traits were evaluated in wheat flag leaves at 10, 20, 30 days after anthesis under drought stress (DS) and well-watered (WW), and quantitative trait loci (QTL) were analyzed. Expression of the traits during the grain filling stage showed downward trends under both conditions, but expression of three phenotypes were stronger under WW than those under DS. Extremely significant positive correlations were established among the traits at all growth stages under both conditions. A total of 18 additive QTLs for those traits were identified on 10 chromosomes. Among them, two batches of nine additive QTLs were associated with the target traits under DS and WW, respectively. Two additive QTLs for gs and E, two for gs and PN, six for gs, PN, and E clustered at the same or near the region (colocation) of chromosomes 4A, 2B, and 7B, respectively. This provided genetic basis for close phenotype correlations among gs, PN, and E. Furthermore, QTLs for gs, PN, and E near Xgwm577 and Xgwm611 located on 7B chromosome were linked to previously reported QTLs regulating a SPAD value and the chlorophyll a/b ratio under dark-induced condition. This finding indicated that these QTLs on 7B chromosome might be involved in the process of wheat leaf senescence., S. G. Wang, S. S. Jia, D. Z. Sun, H. Y. Wang, F. F. Dong, H. X. Ma, R. L. Jing, G. Ma., and Obsahuje bibliografii
Influence of supra-optimal concentrations of K on growth, water relations, and photosynthetic capacity in pearl millet under severe water deficit conditions was assessed in a glasshouse. Nineteen-days-old plants of two lines, ICMV-94133 and WCA-78, of Pennisetum glaucum (L.) R.Br. were subjected for 30 d to 235.0, 352.5, and 470.0 mg(K) kg-1(soil) and two water regimes (100 and 30 % field capacity). Increasing K supply did not alleviate the effect of water deficit on the growth of two lines of pearl millet since additional amount of K in the growth medium had no effect on shoot dry mass, relative growth rate, plant leaf area, net assimilation rate, or leaf area ratio, although there was significant effect of drought stress on these variables. Soil moisture had a significant effect on net photosynthetic rate (PN), transpiration rate, stomatal conductance, and water use efficiency of both pearl millet lines, but there was no significant effect of varying K supply on these variables. In WCA-78 an ameliorative effect of increasing supply of K on PN was observed under water deficit. Chlorophyll (Chl) a and b contents increased significantly in both lines with increase in K supply under well watered conditions, but under water deficit they increased only in ICMV-94133. Chl a/b ratios were reduced significantly in WCA-78 with increasing K supply under both watering regimes, but by contrast, in ICMV-94133 this variable was decreased only under water stress. Leaf water potential and osmotic potential of both lines decreased significantly with the imposition of drought. Leaf pressure potential in both lines increased with increase in K supply under water stress. Contents of total free amino acids in the leaves of both pearl millet lines increased significantly with increase in K supply under water stress. Potassium supply had no effect on leaf soluble sugars or soluble proteins. Considerable osmotic adjustment occurred in pearl millet plants experiencing water deficit under high K supply. and M. Ashraf, Ashfaq Ahmad, T. McNeilly.
We tested the usefulness of chlorophyll a fluorescence quenching analysis for the selection of maize parental inbred lines able to produce F1 hybrids with a high CO2 assimilation rate during growth at suboptimal temperature. Fifty inbred lines, grown at 15 °C, showed at 6 °C a broad genetic variability regarding the quantum yield of photosynthetic electron transport (ΦPS2). A decrease of ΦPS2 in sensitive lines was caused more by reduction of the efficiency of excitation energy capture by open photosystem 2 (PS2) reaction centres (Fv'/Fm') than by a drop in photochemical quenching (qP). Selected inbred lines with the highest (H) and the lowest (L) values of ΦPS2 were used for separate crossings in a diallelic arrangement. Twenty-one of H×H hybrids and 21 of the L×L hybrids were grown at 15 °C. The H×H hybrids showed at suboptimal temperature a significantly higher transport of photosynthetic electrons than the L×L hybrids at lower (400) as well as at higher [800 μmol(photon) m-2 s-1] irradiance. The mean net photosynthetic rate (PN) in H×H and L×L hybrids amounted to 8.4 and 5.8 (second leaf) and 8.5 and 7.6 μmol(CO2) m-2 s-1 (third leaf), respectively. Among the best 20 hybrids with regard to PN (values larger than the average) of second leaves, as many as 15 were derived from H lines (75 % of hybrids), whereas among the best 21 hybrids with regard to PN of the third leaves, 16 were derived from H lines (76 % of hybrids). The intensive PN of H×H hybrids was most often accompanied by less water lost via transpiration in relation to photosynthesis than in the hybrids of L lines. Hence an analysis of chlorophyll a fluorescence quenching enables the selection of inbred lines, which can produce hybrids with improved CO2 fixation and with efficient water management during growth at suboptimal temperature. and J. Kościelniak, F. Janowiak, Z. Kurczych.
Changes in growth parameters and 14CO2 and [U-14C]-sucrose incorporation into the primary metabolic pools and essential oil were investigated in leaves and stems of M. spicata treated with etherel and gibberellic acid (GA). Compared to the control, GA and etherel treatments induced significant phenotypic changes and a decrease in chlorophyll content, CO2 exchange rate, and stomatal conductance. Treatment with etherel led to increased total incorporation of 14CO2 into the leaves wheras total incorporation from 14C sucrose was decreased. When 14CO2 was fed, the incorporation into the ethanol soluble fraction, sugars, organic acids, and essential oil was significantly higher in etherel treated leaves than in the control. However, [U-14C]-sucrose feeding led to decreased label incorporation in the ethanol-soluble fraction, sugars, organic acids, and essential oils compared to the control. When 14CO2 was fed to GA treated leaves, label incorporation in ethanol-insoluble fraction, sugars, and oils was significantly higher than in the control. In contrast, when [U-14C]-sucrose was fed the incorporation in the ethanol soluble fraction, sugars, organic acids, and oil was significantly lower than in the control. Hence the hormone treatment induces a differential utilization of precursors for oil biosynthesis and accumulation and differences in partitioning of label between leaf and stem. Etherel and GA influence the partitioning of primary photosynthetic metabolites and thus modify plant growth and essential oil accumulation. and Preety Singh ... [et al.].
Influence of manganese (Mn) toxicity on photosynthesis in ricebean (Vigna umbellata) was studied by the measurement of gas exchange characteristics and chlorophyll fluorescence parameters. The net photosynthetic rate (PN), transpiration rate (E), and stomatal conductance (gs) were reduced with increasing Mn concentration in nutrient solution. The reduction in gs and E was more pronounced at 6 d of Mn treatment. However, PN declined at 2 d of Mn treatment implying that the reduction in photosynthesis was not due to the direct effect of Mn on stomatal regulation. Mn did not affect the maximum efficiency of photosystem 2 (PS2) photochemistry (Fv/Fm). A reduction in photochemical quenching (qP) and excitation capture efficiency of open PS2 (Fv'/Fm') with a concomitant increase in qN was observed. This implies that reduced demand for ATP and NADPH due to the reduction in photosynthesis causes a down-regulation of PS2 photochemistry and thus a high pH gradient (increase in qN) and limited electron transport (decreased qP). and Desiraju Subrahmanyam, V. S. Rathore.
Spearmint cultivars MSS-5, Arka, and Neera grown in nutrient culture in controlled conditions differed in plant height, number of tillers, internodal position, fresh mass, dry mass, leaf stem ratio, and chlorophyll contents. Initial transpiration rate, stomatal conductivity, and CO2 exchange rate showed better increase in MSS-5 genotype. Mn stress decreased oil content whereas the content of oil constituent carvone increased in MSS-5 and Arka. and P. Singh, A. Misra, N. K. Srivastava.
A gradual reduction in leaf water potential (Ψleaf), net photosynthetic rate (PN), stomatal conductance, and transpiration rate was observed in two drought tolerant (C 306 and K 8027) and two susceptible (RW 893 and 899) genotypes subjected to water stress. The extent of reduction was lower in K 8027 and C 306 and higher in RW 893 and RW 899. Rewatering the plants after 5 d of stress restored PN and other gas exchange traits in all four cultivars. Water stress had no significant effect on variable to maximum fluorescence ratio (Fv/Fm) indicating that water stress had no effect on primary photochemistry of photosystem 2 (PS2). However, water stress reduced the efficiency of excitation energy transfer (F'v/F'm) and the quantum yield of electron transport (ΦPS2). The reduction was more pronounced in susceptible cultivars. Water stress had no significant effect on photochemical quenching, however, the non-photochemical quenching increased by water stress. and D. Subrahmanyam ... [et al.].
Effects of benzyladenine (BA) and abscisic acid (ABA) applied separately or simultaneously on parameters of gas exchange of Phaseolus vulgaris L. leaves were studied. In the first two experimental sets) 100 μM ABA and 10 μM BA were applied to plants sufficiently supplied with water. Spraying of leaves with ABA decreased stomatal conductance (gs) and in consequence transpiration rate (E) and net photosynthetic rate (PN) already 1 h after application, but 24 h after application the effect almost disappeared. 10 μM BA slightly decreased gas exchange parameters, but in simultaneous application with ABA reversed the effect of ABA. Immersion of roots into the same solutions markedly decreased gas exchange parameters and 24 h after ABA application the stomata were completely closed. The effect of ABA was ameliorated by simultaneous BA application, particularly after 1-h treatment. In the third experimental set, plants were pre-treated by immersing roots into water, 1 μM BA, or 100 μM ABA for 24 h and then the halves of split root system were dipped into different combinations of 1 μM BA, 100 μM ABA, and water. In plants pre-treated with ABA all gas exchange parameters were small and they did not differ in plants treated with H2O+H2O, H2O+BA, or BA+BA. In plants pre-treated with BA or H2O, markedly lower values of PN were found when both halves of roots were immersed in ABA. Further, the effects of pre-treatment of plants with water, 1 μM BA, 100 μM ABA, or ABA+BA on the development of water stress induced by cessation of watering and on the recovery after rehydration were followed. ABA markedly decreased gas exchange parameters at the beginning of the experiment, but in its later phase the effect was compensated by delay in development of water stress. BA also delayed development of water stress and increased PN in water-stressed leaves. BA reversed the effect of ABA at mild water stress. Positive effects of BA and ABA pre-treatments were observed also after rehydration.
Variability in leaf gas-exchange traits in thirteen soybean (Glycine max L. Merr) genotypes was assessed in a field experiment conducted at high altitude (1 950 m). Leaf net photosynthetic rate (PN) exhibited a high degree of variability at all the growth stages studied. PN and other gas-exchange parameters exhibited a seasonal pattern that was similar for all the genotypes. PN rate was highest at seed filling stage. PN was positively and significantly associated with aboveground dry matter and seed yield. The area leaf mass (ALM) exhibited a strong positive association with leaf PN, aboveground dry matter, and seed yield. The positive association between ALM, PN, and seed yield suggests that this simple and easy to measure character can be used in breeding programmes as a surrogate for higher photosynthetic efficiency and eventually higher yield.