Photosynthetic Responses for Vitis vinifera Plants Grown at Different Photon Flux Densities Under Field Conditions

In grapevine (Vitis vinifera L.) leaf chlorophyll (Chl) a and Chl b and carotenoid contents were higher in plants grown at low photon flux densities (PFD) than in those grown at medium and high PFD. The highest Chl a variable to maximum fluorescence ratio F_v/F_m was observed in plants grown at medium PFD while the minimum fluorescence F₀ was highest in those at high PFD. In isolated thylakoids, both high and low PFD caused marked inhibition of whole chain and photosystem 2 (PS2) activities. The artificial exogenous electron donor diphenyl carbazide significantly restored the loss of PS2 activity in low PFD leaves.     

Responses of Photosynthetic Rate and Stomatal Conductance to Water Stress in Soybean Leaves

Responses of photosynthetic rate and stomatal conductance to water stress as weI1 as the relationship between photosynthetic rate and stomatal conductance were investigated with soybean cultivars “Ludou No. 4” and “7605”. The former was a high yield cultivars widely used in Shandong province, and the latter was a small grain soybean line bred by Shandong Academy of Agricultural science. Soil water stress decreased leaf apparent photosynthetic rate and stomatal conductance of two soybean cultivars, and “Ludou No. 4” decreased more than “7605”. At the same value of water potential, photosynthetic rate and stomatal conductance of “7605” were higher than those of “Ludou No,4”,but the rate of stomatal closure for “7605” was higher than “Ludou No. 4”. Decreasing of stomatal conductance caused rising of leaf temperature of two soybean cultivars, and the rising of “7605” was more rapid than “Ludou No. 4”, but at the same treatment of water stress, leaf temperature of “Ludou No. 4” was higher than “7605”. Leaf water use efficiecy (WUE) of two soybean cultivars were decreased under water stress, and the rate of decreasing in “Ludou No.4” was more rapid than in “7605”. These results showed that “7605” was more resistant to water:stress than “Ludou No. 4”.     

不同菠菜品种对海水胁迫的生理响应差异

以耐海水菠菜品种荷兰3号和海水敏感品种圆叶菠菜为材料,采用水培方法,研究了海水胁迫对菠菜叶片、根系质膜的伤害作用以及叶片光合作用、叶绿素荧光参数的影响.结果表明:(1)海水胁迫对荷兰3号单株干重影响不大,而显著降低圆叶菠菜的单株干重,并使2个品种植株的叶片和根系MDA含量增加,质膜透性增大,叶片光合色素含量降低,但荷兰3号的变化幅度(叶片MDA除外)小于圆叶菠菜.(2)海水胁迫下,短期内2个品种由于气孔限制引起叶片胞间CO2浓度(Ci)降低,净光合速率(Pn)下降;长期胁迫下,荷兰3号Pn恢复到对照水平,而圆叶菠菜同化力下降,Pn降低.(3)海水胁迫对荷兰3号光化学猝灭系数(qP)影响不大,实际光化学效率(ΦPSⅡ)明显升高,而圆叶菠菜的qP和ΦPSⅡ均下降;荷兰3号初始荧光(F0)的下降幅度和非光化学猝灭系数(qN)上升幅度比圆叶菠菜大;2个菠菜品种的最大光化学效率(Fv/Fm)均下降,但荷兰3号光抑制程度(1-qP/qN)的升高幅度比圆叶菠菜小.研究结果说明,海水胁迫下,2个耐性不同的菠菜品种植株都产生了光合作用的光抑制和光氧化伤害,使膜质过氧化和叶绿素含量降低;耐性强的品种能够较多地将光能用于光化学反应,热耗散能力较强,光抑制程度较低,膜系统和光合色素受到活性氧的破坏程度较低,保持了较高的净光合速率,最终可明显降低海水胁迫对植株生长的影响.     

Effects of Ultraviolet-B Irradiance on Soybean : V. The Dependence of Plant Sensitivity on the Photosynthetic Photon Flux Density during and after Leaf Expansion

Soybeans (Glycine max [L.] Merr. cv Essex) were grown in a green-house, and the first trifoliate leaf was either allowed to expand under a high photosynthetic photon flux density (PPFD) (1.4 millimoles per square meter per second) or a low PPFD (0.8 millimoles per square meter per second). After full leaf expansion, plants from each treatment were placed into a factorial design experiment with two levels of ultraviolet-B (UV-B) radiation (0 and 80 milliwatts per square meter biologically effective UV-B) and two levels of concomitant PPFD (0.8 and 1.4 millimoles per square meter per second) resulting in a total of eight treatments. Measurements of net photosynthesis and the associated diffusion conductances, ribulose-1,5-bisphosphate carboxylase activity, chlorophyll and flavonoid concentrations, and leaf anatomy were examined for all treatments. Leaves expanded in the high PPFD were unaffected by UV-B radiation while those expanded in the low PPFD were sensitive to UV-B-induced damage. Likewise, plants which were UV-B irradiated concomitantly with the high PPFD were resistant to UV-B damage, while plants irradiated under the low PPFD were sensitive. The results of this study indicate that both anatomical/morphological and physiological/biochemical factors contribute toward plant sensitivity to UV-B radiation.     

Photosynthetic Responses of a Temperate Liana to Xylella fastidiosa Infection and Water Stress

Xylella fastidiosa is a xylem‐limited bacterial plant pathogen that causes bacterial leaf scorch in its hosts. Our previous work showed that water stress enhances leaf scorch symptom severity and progression along the stem of a liana, Parthenocissus quinquefolia, infected by X. fastidiosa. This paper explores the photosynthetic gas exchange responses of P. quinquefolia, with the aim to elucidate mechanisms behind disease expression and its interaction with water stress. We used a 2 × 2‐complete factorial design, repeated over two growing seasons, with high and low soil moisture levels and infected and non‐infected plants. In both years, low soil moisture levels reduced leaf water potentials, net photosynthesis and stomatal conductance at all leaf positions, while X. fastidiosa‐infection reduced these parameters at basally located leaves only. Intercellular CO₂ concentrations were reduced in apical leaves, but increased at the most basal leaf location, implicating a non‐stomatal reduction of photosynthesis in leaves showing the greatest disease development. This result was supported by measured reductions in photosynthetic rates of basal leaves at high CO₂ concentrations, where stomatal limitation was eliminated. Repeated measurements over the summer of 2000 showed that the effects of water stress and infection were progressive over time, reaching their greatest extent in September. By reducing stomatal conductances at moderate levels of water stress, P. quinquefolia maintained relatively high leaf water potentials and delayed the onset of photosynthetic damage due to pathogen and drought‐induced water stress. In addition, chlorophyll fluorescence measurements showed that P. quinquefolia has an efficient means of dissipating excess light energy that protects the photosynthetic machinery of leaves from irreversible photoinhibitory damage that may occur during stress‐induced stomatal limitation of photosynthesis. However, severe stress induced by disease and drought eventually led to non‐stomatal decreases in photosynthesis associated with leaf senescence.     

Dynamic Balancing of Isoprene Carbon Sources Reflects Photosynthetic and Photorespiratory Responses to Temperature Stress

The volatile gas isoprene is emitted in teragrams per annum quantities from the terrestrial biosphere and exerts a large effect on atmospheric chemistry. Isoprene is made primarily from recently fixed photosynthate; however, alternate carbon sources play an important role, particularly when photosynthate is limiting. We examined the relative contribution of these alternate carbon sources under changes in light and temperature, the two environmental conditions that have the strongest influence over isoprene emission. Using a novel real-time analytical approach that allowed us to examine dynamic changes in carbon sources, we observed that relative contributions do not change as a function of light intensity. We found that the classical uncoupling of isoprene emission from net photosynthesis at elevated leaf temperatures is associated with an increased contribution of alternate carbon. We also observed a rapid compensatory response where alternate carbon sources compensated for transient decreases in recently fixed carbon during thermal ramping, thereby maintaining overall increases in isoprene production rates at high temperatures. Photorespiration is known to contribute to the decline in net photosynthesis at high leaf temperatures. A reduction in the temperature at which the contribution of alternate carbon sources increased was observed under photorespiratory conditions, while photosynthetic conditions increased this temperature. Feeding [2-¹³C]glycine (a photorespiratory intermediate) stimulated emissions of [¹³C_1–5]isoprene and ¹³CO₂, supporting the possibility that photorespiration can provide an alternate source of carbon for isoprene synthesis. Our observations have important implications for establishing improved mechanistic predictions of isoprene emissions and primary carbon metabolism, particularly under the predicted increases in future global temperatures.Many plant species emit isoprene (2-methyl-1,3-butadiene [C₅H₈]) into the atmosphere at high rates (Sharkey and Yeh, 2001). With an estimated emission rate of 500 to 750 teragram per year by terrestrial ecosystems (Guenther et al., 2006), isoprene exerts a strong control over the oxidizing capacity of the atmosphere. Due to its high reactivity to oxidants, it fuels an array of atmospheric chemical and physical processes affecting air quality and climate, including the production of ground-level ozone in environments with elevated concentrations of nitrogen oxides (Atkinson and Arey, 2003; Pacifico et al., 2009) and the formation/growth of organic aerosols (Nguyen et al., 2011). At the plant level, isoprene provides protection from stress, through stabilizing membrane processes (Sharkey and Singsaas, 1995; Velikova et al., 2011) and/or reducing the accumulation of damaging reactive oxygen species in plant tissues under stress (Loreto et al., 2001; Vickers et al., 2009b; Velikova et al., 2012). While the mechanism(s) are still under investigation, isoprene may directly or indirectly stabilize hydrophobic interactions in membranes (Singsaas et al., 1997), minimize lipid peroxidation (Loreto and Velikova, 2001), and directly react with reactive oxygen species (Kameel et al., 2014), yielding first-order oxidation products methyl vinyl ketone and methacrolein (Jardine et al., 2012, 2013). The two main environmental drivers for global changes in isoprene fluxes are light and temperature (Guenther et al., 2006). Isoprene production is closely linked to net photosynthesis, and both isoprene emissions and net photosynthesis are controlled by light intensity (Monson and Fall, 1989). There is also a positive correlation between net photosynthesis and isoprene emissions as leaf temperatures increase up to the optimum temperature for net photosynthesis (Monson et al., 1992).Despite the close correlation between photosynthesis and isoprene emissions, plant enclosure observations and leaf-level analyses have both shown that the fraction of net photosynthesis dedicated to isoprene emissions is not constant. During stress events that decrease net photosynthetic rates, isoprene emissions are often less affected or even stimulated; this results in an increase in relative isoprene production from 1% to 2% of net photosynthesis under normal conditions to 15% to 50% under extreme stress (Goldstein et al., 1998; Fuentes et al., 1999; Kesselmeier et al., 2002; Harley et al., 2004). In severe stress conditions such as drought, isoprene emissions can even continue in the complete absence of photosynthesis (Fortunati et al., 2008). An uncoupling of isoprene emissions from net photosynthesis has also been observed in a number of other studies where the optimum temperature for isoprene emissions was found to be substantially higher than that of net photosynthesis; under the high-temperature conditions, isoprene emissions can account for more than 50% of net photosynthesis (Sharkey and Loreto, 1993; Lerdau and Keller, 1997; Harley et al., 2004; Magel et al., 2006).Analyses of carbon sources using ¹³CO₂ leaf labeling have revealed that under standard conditions (i.e. leaf temperature of 30°C and photosynthetically active radiation [PAR] levels of 1,000 µmol m^–2 s^–1), isoprene is produced primarily (70%–90%) using carbon directly derived from the Calvin cycle (Delwiche and Sharkey, 1993; Affek and Yakir, 2002; Karl et al., 2002) via the chloroplastic methylerythritol phosphate (MEP) isoprenoid pathway (Zeidler et al., 1997). The relative contributions of photosynthetic and alternate carbon sources for isoprene are now recognized as being variable under different environmental conditions. Changes in net photosynthesis rates under drought stress (Funk et al., 2004; Brilli et al., 2007), salt stress (Loreto and Delfine, 2000), and changes in ambient O₂ and CO₂ concentrations (Jones and Rasmussen, 1975; Karl et al., 2002; Trowbridge et al., 2012) alter their relative contributions. Under heat stress-induced photosynthetic limitation in Populus deltoides (a temperate species), an increase in the relative contribution of alternate carbon sources was also observed (Funk et al., 2004). However, our current understanding of the responses of isoprene carbon sources to changes in temperature and light levels is poor, and the connection(s) of these responses to changes in leaf primary carbon metabolism (e.g. photosynthesis, photorespiration, and respiration) remains to be determined.Studies over the last decade have shown or suggested that potential alternate carbon sources include refixation of respired CO₂ (Loreto et al., 2004), intermediates from the cytosolic mevalonate (MVA) isoprenoid pathway (Flügge and Gao, 2005; Lichtenthaler, 2010), and intermediates from central carbon metabolism, including pyruvate (Jardine et al., 2010), phosphoenolpyruvate (Rosenstiel et al., 2003), and Glc (Schnitzler et al., 2004). Over 40 years ago, it was also proposed that photorespiratory carbon could directly contribute to isoprene production in plants (Jones and Rasmussen, 1975); however, subsequent studies (Monson and Fall, 1989; Hewitt et al., 1990; Karl et al., 2002) have concluded that photorespiration does not contribute to isoprenoid production.In this study, we examined the carbon composition of isoprene emitted from tropical tree species under changes in light and temperature, the two key environmental variables that affect isoprene emissions. Using a novel real-time analytical approach, we were able to observe compensatory changes in carbon source contribution to isoprene during thermal ramping at high temperatures, despite the overall isoprene emissions remaining relatively stable. By conducting leaf temperature curves under variable ¹³CO₂ concentrations and applying [2-¹³C]Gly leaf labeling, we also reopen the discussion on the role of photorespiration as an alternate source of carbon for isoprenoid formation.     

Stress Tolerance Parameters in Different Genotypes of Soybean

Free proline content, superoxide-dismutase activity, and lipid peroxidation were measured in sixteen Yugoslav and introduced genotypes of soybean. More tolerant genotypes with higher free proline content and high superoxide-dismutase activity, and low lipid peroxidation were chosen. The selected genotypes could be used in field production, as well as in breeding.     

罗布麻对不同浓度盐胁迫的生理响应

利用网室盆栽实验,研究不同浓度的NaCl（100-400mmol·L^-1）胁迫对罗布麻（Apocynum venetum）生长及生理特性的影响。结果表明,100mmol·L^-1NaCl处理显著降低了罗布麻植株的鲜重,但对其干重影响不大;随着盐浓度继续增加,罗布麻鲜重和干重显著下降。在盐胁迫下,罗布麻叶片内的丙二醛含量、电解质渗漏率、根部和地上部Na^＋的含量明显增加,K^＋的含量随着盐离子浓度的增加而降低。盐胁迫显著降低了地上部Ca^2＋的含量,而对根部Ca^2＋的含量没有影响。植株K^＋/Na^＋和Ca^2＋/Na^＋比值随着盐胁迫强度的增加而降低。盐胁迫显著促进了罗布麻根部对K^＋和Ca^2＋的选择性吸收及对K^＋的选择性运输。当NaCl浓度小于或等于200mmol·L^-1时,随着盐离子浓度的增加,罗布麻叶片内的脯氨酸和可溶性糖积累显著增加,而当NaCl浓度大于200mmol·L^-1时,这2种有机溶质含量显著下降。总体上,罗布麻通过积累无机离子、合成有机溶质及维持较高的K^＋、Ca^2＋选择性吸收和运输来适应一定浓度（≤200mmol·L^-1NaCl）的盐胁迫。     

不同磷效率小麦品种对缺磷胁迫反应的比较

在营养液培养条件下,以根据相对产量为指标筛选出的6个不同磷效率的小麦(Triticum aestivum L.)品种为材料,对其苗期在缺磷条件下生长、根冠磷含量及其分配,以及叶片韧皮部汁液中磷浓度等进行了比较研究.结果表明,缺磷抑制植株地上部生长,但刺激根系生长,导致植株根/冠比增加.无论在供磷或缺磷条件下,磷高效品种的根冠生长速率都低于磷低效品种.缺磷导致植株体内的磷含量下降与根系相比,地上部磷含量的下降速率更快.但在缺磷条件下,不同磷效率的小麦品种根冠间的磷分配变化没有差异.研究发现,在正常供磷条件下,磷高效小麦品种的叶片韧皮部汁液中磷浓度较低,而磷低效品种的叶片韧皮部汁液中磷浓度较高.但开始缺磷后,磷高效品种的叶片韧皮部汁液中的磷浓度下降较慢,使其相对磷浓度较高.缺磷后1 0天,磷低效品种叶片韧皮部汁液中的磷浓度为供磷对照的35.9%,而磷高效品种叶片韧皮部汁液中的磷浓度为供磷对照的59%.     

罗布麻对不同浓度盐胁迫的生理响应

利用网室盆栽实验, 研究不同浓度的NaCl(100–400 mmol·L^–1)胁迫对罗布麻(Apocynum venetum)生长及生理特性 的影响。结果表明, 100 mmol·L^–1NaCl处理显著降低了罗布麻植株的鲜重, 但对其干重影响不大; 随着盐浓度继续增加, 罗布麻鲜重和干重显著下降。在盐胁迫下, 罗布麻叶片内的丙二醛含量、电解质渗漏率、根部和地上部Na⁺的含量明显增加, K⁺的含量随着盐离子浓度的增加而降低。盐胁迫显著降低了地上部Ca²⁺的含量, 而对根部Ca²⁺的含量没有影响。植株K⁺/Na⁺和Ca²⁺/Na⁺比值随着盐胁迫强度的增加而降低。盐胁迫显著促进了罗布麻根部对K⁺和Ca²⁺的选择性吸收及对K⁺的选择性运输。当NaCl浓度小于或等于200 mmol·L^–1时, 随着盐离子浓度的增加, 罗布麻叶片内的脯氨酸和可溶性糖积累显著增加,而当NaCl浓度大于200 mmol·L^–1时, 这2种有机溶质含量显著下降。总体上, 罗布麻通过积累无机离子、合成有机溶质及维持较高的K⁺、Ca²⁺选择性吸收和运输来适应一定浓度(≤200 mmol·L^–1NaCl)的盐胁迫。     

不同磷效率小麦品种对缺磷胁迫反应的比较

在营养液培养条件下,以根据相对产量为指标筛选出的6个不同磷效率的小麦(Triticum aestivum L.)品种为材料,对其苗期在缺磷条件下生长、根冠磷含量及其分配,以及叶片韧皮部汁液中磷浓度等进行了比较研究。结果表明,缺磷抑制植株地上部生长,但刺激根系生长,导致植株根／冠比增加。无论在供磷或缺磷条件下,磷高效品种的根冠生长速率都低于磷低效品种。缺磷导致植株体内的磷含量下降与根系相比,地上部磷含量的下降速率更快。但在缺磷条件下,不同磷效率的小麦品种根冠间的磷分配变化没有差异。研究发现,在正常供磷条件下,磷高效小麦品种的叶片韧皮部汁液中磷浓度较低,而磷低效品种的叶片韧皮部汁液中磷浓度较高。但开始缺磷后,磷高效品种的叶片韧皮部汁液中的磷浓度下降较慢,使其相对磷浓度较高。缺磷后10天,磷低效品种叶片韧皮部汁液中的磷浓度为供磷对照的35．9％,而磷高效品种叶片韧皮部汁液中的磷浓度为供磷对照的59％。     

Responses of Quercus ilex from Different Provenances to Experimentally Imposed Water Stress

Responses of Quercus ilex L. seedlings from three different localities in Italy to experimentally imposed drought stress were analysed. Predawn (Ψ_pd) and midday (Ψ_m) leaf water potential of stressed seedlings decreased on an average until −4.0 and −4.2 MPa, respectively, in the severe water stress. At the end of the severe water stress the relative water content (RWC) was 72.5 – 83.6 % and the photosynthetic rates (P_N) near zero. The critical threshold value of Ψ_pd for complete stomatal closure was from −4.0 to −4.5 MPa. The leaf damage after the severe water stress was significantly greater in seedlings originated from the acorns of climax area (45 % total leaf injured area and 40 % fallen leaves) than in the other seedlings (on an average 20.5 % total leaf injured area and 21 % fallen leaves). This revised version was published online in July 2006 with corrections to the Cover Date.     

Adrenal Responses to Stress

Based on concepts proposed by Langley, Cannon, and Selye, adrenal responses to stress occur in a syndrome that reflects activation of the sympathoadrenal system and hypothalamic–pituitary–adrenocortical (HPA) axis; and a “stress syndrome” maintains homeostasis in emergencies such as “fight or flight” situations, but if the stress response is excessive or prolonged then any of a variety of clinical disorders can arise. The idea of a unitary sympathoadrenal system does not account for evidence that different stressors elicit different patterns of autonomic responses, with exposure to some stressors differentially affecting sympathetic noradrenergic and adrenomedullary hormonal activities. Instead, adrenomedullary responses to stressors are more closely tied to adrenocortical than to sympathetic noradrenergic responses. Distress involves concurrent activation of the HPA and adrenomedullary neuroendocrine systems.     

The Monomolecular and Rectangular Hyperbola as Empirical Models of the Response of Photosynthetic Rate to Photon Flux Density, with Applications to Three Veronica Species

The properties of the rectangular hyperbola and monomolecularfunctions, with respect to the photosynthesis/photon flux density(PFD) relationship, are discussed, and the shortcomings of theformer are highlighted. Both models were fitted to data acquiredfrom three closely related Veronica species of contrasting ecology.The non-linear regression algorithms give estimates, with standarderrors, of light saturated photosynthetic rate, light compensationpoint, dark respiration rate, and photochemical efficiency atlow PFD. While the rectangular hyperbola gave almost as gooda fit to the data as the monomolecular for each species, thelight saturated photosynthetic rate estimate given by the formerwas always unacceptably high in comparison with that indicatedby the obvious trend of the data. Moreover, this tendency wasaccentuated if near-saturating PFDs were removed from data sets,and there was a tendency for the fitting algorithm to becomeunstable. No such problems were encountered with the monomolecularfunction, and it is suggested that this be used whenever a simpleempirical model is required to analyze photosynthesis/PFD data. Veronica montana L, Veronica chamaedrys L, Veronica officinalis L, wood speedwell, Germander speedwell, common speedwell, empirical mathematical model, monomolecular function, rectangular hyperbola function, nonlinear regression, photosynthesis, photon flux density, light saturated photosynthetic rate, light compensation point, photochemical efficiency, dark respiration rate     

干旱胁迫下油橄榄品种光合特性研究

为揭示油橄榄(Olea europaea L.)耐旱性与光合特性之间的关系,以筛选出的适宜于半干旱川西南地区种植的7个引进油橄榄品种为供试材料,采用盆栽模拟干旱胁迫的方法,研究持续干旱胁迫对其光合特性的影响。结果表明:(1)随着干旱胁迫程度加剧,7个油橄榄品种叶片相对含水量均显著降低,至干旱胁迫后期(25d),各品种叶片均出现大幅失水,其中品种‘科拉蒂’失水率最高(45.79%),而品种‘小苹果’失水率最低(25.52%),说明‘小苹果’叶片在干旱胁迫下较其他油橄榄品种具有更高保水能力。(2)随着干旱胁迫程度加剧,7个油橄榄品种叶片光合色素含量均不同程度降低,表明光合色素分解量大于合成量;干旱胁迫持续25d时,品种‘豆果’的叶绿素a和叶绿素b含量下降幅度最大(P0.05),品种‘皮削利’类胡萝卜素含量下降幅度最大(P0.05),而品种‘小苹果’叶绿素a含量下降幅度最小。(3)随着干旱胁迫的持续进行,各油橄榄品种叶片净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和胞间CO2浓度(Ci)均不同程度降低,而水分利用效率(WUE)则呈上升趋势;干旱胁迫期间,品种‘佛奥’的Pn、Tr和Ci以及‘皮削利’的Gs降幅均高于其他品种,而‘小苹果’的Pn、Gs和Ci降幅均为最小且WUE上升幅度最大。研究发现,在持续干旱胁迫条件下,油橄榄幼苗叶片均大幅失水,光合色素结构被破坏、色素分解、含量降低,同时气孔关闭蒸发减少,光合作用减弱,而供试油橄榄品种中‘小苹果’对干旱胁迫的适应性最强,适宜于在半干旱的川西地区种植。     

不同品种春小麦根系对低钾胁迫的生物学响应

采用水培法,以3个春小麦品种(加春1号、2号、4号)为试验材料,研究了低钾胁迫下不同品种春小麦根系的形态学与生理学特征。结果表明:(1)与对照相比,低钾胁迫下小麦的根重、根数、总根长、总吸收面积、根活力、根系SOD及POD活性、根系活性吸收面积均明显降低,但根冠比有所增加,不同春小麦品种间的变化趋势相似,但变化幅度存在明显差异。(2)供试品种小麦根系的形态与生理学特征在同一供钾水平下和不同供钾水平间均存在着明显的差异,表明这两种性状的差异是由基因型和环境因素共同决定的,因此,根系形态学和生理学特征可以作为筛选高效吸收钾小麦品种的参考指标。(3)供试的3个春小麦品种中‘加春4号’对低钾环境的适应性最强。     

红芽芋驯化苗对盐胁迫的光合及生理响应

为探讨江西铅山红芽芋的耐盐机制,以其组培移栽驯化苗为材料,研究了盐胁迫对其生物量积累、光合特性、荧光特性等抗逆生理特性的影响。结果表明:（1）红芽芋幼苗生物量和根冠比在低盐胁迫下（50 mmol·L^-1）得到显著促进,而在高盐胁迫下（100～250 mmol·L^-1）受到显著抑制。（2）低盐胁迫幼苗的净光合速率（P_n）、气孔导度（G_s）、气孔限制值（L_s）、水分利用效率（WUE）和瞬时羧化效率（CUE）比对照（0 mmol·L^-1）显著增加,细胞间CO₂浓度（C_i）比对照显著下降,蒸腾速率（T_r）与对照无显著差异;高盐胁迫幼苗的P_n、L_s、WUE、CUE和G_s较对照显著下降,C_i比对照显著增加。（3）低盐胁迫幼苗的最大荧光（F_m）、PSⅡ潜在光化学效率（F_v/F₀）和光化学猝灭系数（q_P）比对照显著增加,初始荧光（F₀）较对照显著下降,PSⅡ最大光化学效率（F_v/F_m）、PSⅡ实际光化学效率（Φ_PSⅡ）、开放的PSⅡ反应中心捕获激发能效率（F_v′/F_m′）和非光化学猝灭系数（NPQ）与对照无显著差异;而高盐胁迫幼苗的F₀、F_m、F_v/F_m、F_v/F₀、Φ_PSⅡ、F_v′/F_m′和q_P均较对照显著下降,NPQ比对照显著增加。（4）各盐胁迫幼苗叶片的可溶性蛋白含量以及过氧化物酶、超氧化物歧化酶和过氧化氢酶活性与对照相比先升后降,并以低盐下最高;可溶性总糖和脯氨酸含量均比对照显著增加;丙二醛含量和质膜透性相对值在低盐胁迫下无显著变化,而在高盐下显著增加;叶绿素含量和根系活力在低盐胁迫下无显著变化,而在高盐胁迫后开始显著下降。研究发现,江西铅山红芽芋移栽驯化苗的耐盐阈值为 50 mmol·L^-1,其能够诱导提高叶片可溶性蛋白含量和主要保护酶活性,稳定质膜透性、叶绿素含量和根系活力,增加PSⅡ潜在光化学效率,提高PSⅡ的电子传递活性,维持PSⅡ实际光化学效率,有效启动非辐射热能量耗散机制来保护了光合机构,最终提高净光合速率,增加生物量。     

3种荒漠植物光合及叶绿素荧光对干旱胁迫的响应及抗旱性评价

利用盆栽试验结合人工浇水后自然耗水的方法测定干旱胁迫对梭梭、白刺、沙蒿3种荒漠植物叶片水分、光合及叶绿素荧光参数的影响,探讨各指标在干旱胁迫过程中的变化特征、响应机制及其与土壤水分的定量关系,并用隶属函数法对其进行抗旱性排序。结果表明：(1)3种植物叶片相对含水量(RWC)随干旱胁迫天数增加持续降低,最大水分亏缺(RWD)呈波动式上升趋势。(2)3种植物总叶绿素含量(Chl)和叶绿素a(Chla)、叶绿素b(Chlb)含量,以及梭梭、白刺类胡萝卜素含量均随胁迫天数增加而降低;沙蒿类胡萝卜素随土壤含水率降低逐渐升高。(3)梭梭、白刺、沙蒿叶片净光合速率(P_n)、蒸腾速率(T_r)、水分利用效率(WUE)等主要光合气体交换参数对土壤水分表现出明显的阈值响应,适宜的土壤含水率分别为8.04%～19.33%、4.17%～19.10%、6.48%～17.51%。(4)3种植物 PSⅡ最大光化学效率(Fv/F_m)、实际光化学效率(F_v′/F_m′)及光化学淬灭系数(qP)均随干旱胁迫天数增加和光照强度增大而降低,非光化学淬灭系数(NPQ)则呈逐渐上升趋势;干旱胁迫中后期,梭梭、沙蒿的F_v/F_m及F_v′/F_m′均下降,光合机构光合活性遭到破坏,电子传递受阻,PSⅡ反应中心受损,表现出光抑制,而白刺调节自身PSⅡ反应中心免受伤害的能力较强。(5)隶属函数法综合分析表明,3种植物耐旱能力大小依次为白刺>梭梭>沙蒿。研究发现,3种荒漠植物均可通过调节 PSⅡ反应中心开放程度与活性,对干旱胁迫表现出较强的耐性,胁迫后期植物PSⅡ反应中心关闭或不可逆失活,表现出光抑制。