Papers by Keyword: Stomatal Conductance

Abstract: Much progress has been made toward understanding plant drought resistance. However, the coordinate responses of plant to drought on the basis of ABA level at physiological, ecological and molecular levels remains unclear. Here, the potted winter wheat (triticum aestivum) was cultivated under relative soil moisture (RSM ) respectively at 85% (well-watered), 65% (moderate stress), and 45% (severe stress), and a series of physiological and ecological parameters including ABA level, stomatal conductance, leaf temperature, leaf water potential, together with transcripts of ABA biosynthesis-metabolism key genes including 9-cis-epoxycarotenoid dioxygenase (TaNCED), ABA glucosyltransferase (TaGT), ABA 8'-hydroxylase (TaCYP707A), and β-glucosidase (TaBG) were carried out. We found that ABA contents responsive to soil water loss increased rapidly and showed a significantly-negative correlation with the stomatal conductance and the leaf water potential and a significantly-positive correlation with the leaf-air temperature difference, respectively. The continuous accumulation of ABA was resulted mainly from the increased transcripts of both TaNCEDs and TaBGs genes. The transcripts of TaCYP707A1 and TaGT declined sharply from 85% to 65% RSM and then increased slightly from 65% to 45% RSM, indicating that ABA metabolism not only accelerates the accumulation of ABA level but also contributes to maintain ABA homeostasis. In conclusion, the macroscopic-microscopic changes responsive to water deficient reflects the ABA-regulated, drought-resistance coordinate mechanisms at physiological, ecological and molecular levels in triticum aestivum.

Abstract: Response of gas exchange to VPD in leaves of four trees (Prunus serrulata, Prunus lannesiana, Populus deltoides I-69 (I-69) and Populus × euramericana Neva (I-107)) at the campus of Shandong University in Jinan, Shandong Province were measured. The result showed that: the stomatal conductance increased with increasing VPD, and g_s reached g_s-max at intermediate VPD, and a steady decline in g_s with further increases in VPD. This response pattern was fitted by a parabolic curve (g_s=aD²+bD+c, D=VPD, R²>0.52). The g_s-max at intermediate VPD with changing VPD showed that there was an optimal VPD (or RH) to plants. Therefore, while VPD (or RH) was higher or lower than the optimal VPD (or RH) of plant, g_s would decrease. The response of g_s to VPD in I-69 and I-107 were much more sensitive than P. serrulata and P. lannesiana.

Abstract: This experiment aimed to evaluate the leaf chlorophyll fluorescence and gas exchange response to drought conditions of young rubber plants with different scions. Buds from four genotypes of a progeny derived from crossed clones of RRIM600 x RRII105 from Nongkhai Rubber Research Center, T187, T186, T149 and T172, were grafted to RRIM 600 rootstocks. Eight-month old plants with two flushes were used in this study. Two levels of water treatment were used, drought condition (W₁) and well-watered as control (W₀). Leaf chlorophyll fluorescence, stomatal conductance (g_s) and net photosynthesis rate (Pn) were investigated in three phases: before drought, during drought and after re-watering. Leaf gas exchange parameters were measured using Li-6400 (LiCor Inc.). Leaf chlorophyll fluorescence was measured using FluorPen FP 100 (Photon Systems Instruments). Before drought, genotype T186 had the greatest net photosynthesis rates followed by T172, T187 and T149; there was no difference in maximum quantum yield of photosystem II (F_v/F_m) and performance index on absorption basis (PI_ABS). Drought conditions caused reduction in stomatal conductance, net photosynthesis rates, and leaf chlorophyll fluorescence in all genotypes. In re-watering conditions, genotype T186 and T172 experienced quick recovery while the others showed partial recovery but the values of all parameters did not reach previous levels before treatment.

Abstract: The low concentration of SO₂ in the air can promote stomata opening of plants and improving plant photosynthetic rate, but the gradual accumulation of SO₂ on plant leaves can convert the chlorophyll into phaeophytin, which has no photosynthetic activity, and then affect the plant growth and crop production. After Fumigation with SO₂ in soybean under several different concentrations (4 µl/l,10 µl/l,20 µl/l,40 µl/l) and time spans(1h,2h,4h) respectively, the photosynthesis and gas exchange characteristics were determined. The experimental data showed: (1) with the increasing of concentration and time for fumigation, SO₂ had a great adverse effect on photosynthesis in soybean. Such as the light saturation point of plants decreased, the light compensation point increased, and the maximum net photosynthetic rate reduced significantly (e.g., fumigation with SO₂,4-40 µl/l-4 h, Anmax reduced 29.5% to control) compared with the control plants’. (2)After all kinds processing time, low concentration of fumigation (4µl/l) caused larger stomatal conductance than control. However, the other treatments caused smaller gs than control. (3)gs revealed significant positive correlation with transpiration rate(E), each treatment and control shows r ≥0.9,P2. (5)Concentration of chlorophyll was no insignificant differences with the control at different treatments. After fumigation, the range of chlorophyll a / b was 1.39~1.61 and there was no big difference from control (chlorophyll a / b is 1.49), except the treatment of 20µl/l-1h, which had a significant decline in chlorophyll b (chlorophyll a / b is 1.71).Results: (1) SO₂ concentration had greater impact on soybean than time of fumigation, and the impact of high concentration in short time on soybean was obviously significant. (2) SO₂ fumigation in short time and low concentration can promote stomata open, however SO₂ also can damage the photosynthetic activity of chlorophyll. After a long time of fumigation, photosynthetic rate decreased rapidly, even if gs increased.

Abstract: A reflection function was established, based on leaf gas exchange process and tested with experimental data of eight kinds of plants, i.e. tomato, muskmelon, capsicum, maize, grape, onion, Haloxylon Ammodendron Bunge and Caragana Karshiskii Kom, with multifarious biological characteristic, water and growing status. The function indicated that the leaf stomatal conductance could be linearly reflected by the ratio of humidity and CO2 concentration at leaf surface, and the behaviour of its slope could be recognized as an indicator of leaf gas exchange efficiency, which had a negative relationship with leaf water use efficiency (WUE). The results maybe increase our understanding of potential influences of leaf stomatal conductance on photosynthetic and transpiration gas exchange and leaf WUE.