Eco-physiological and Antioxidant Responses of Holm Oak (<Emphasis Type="Italic">Quercus ilex</Emphasis> L.) Leaves to Cd and Pb

Plants of the urban environment are exposed to a wide range of pollutants, including heavy metals. This research studies in situ the eco-physiological and antioxidant responses of holm oak (Q. ilex) leaves to Pb and Cd to assess the mechanisms of metal tolerance in this species, widely used as biomonitor. Leaves of plants grown at parks and roadsides were analyzed for photosynthetic activity, Pb and Cd concentration in tissues and cell-free extracts, thiol groups, D1 and Rubisco protein content, ascorbic acid (AsA) amount, and catalase (CAT) activity. The main results evidenced that Cd concentration was higher in leaves collected at the park out from the downtown; whereas Pb was most abundant in leaves sampled at the roadside nearby the highway. Pb in cell-free extracts was higher in park than in roadside leaves. Although Cd in the leaf tissues was twofold lower than Pb, it was more abundant than Pb in cellular extracts deprived of all particulate matter. Leaves responded to different concentration of Cd and Pb modulating some eco-physiological and biochemical traits, roadside leaves showed reduced leaf lamina, higher content of photosynthetic pigments, hydrogen peroxide, and AsA, as well as higher CAT activity compared to park leaves. In the roadside leaves, a stress condition for photosynthetic apparatus can be hypothesized on the basis of the decline of photochemical activity, the increase of NPQ, and the reduction of Rubisco and D1 protein content. The elevated presence of thiol groups in these leaves suggests a possible role of Pb and Cd in activation of antioxidant responses.     

Ranges of nutrient concentrations in Quercus ilex leaves at natural and urban sites

The leaf nutrient concentrations and the N‐to‐nutrient ratios were analyzed to evaluate the nutritional status of holm oaks (Quercus ilex L.) experiencing various anthropogenic pressures. Leaves (1 year old) of Q. ilex and surface soil (0–5 cm) surrounding the trees were collected at seven natural and seven urban sites in Campania Region (Southern Italy) and analyzed for the concentrations of macro (C, N, P, S) and micronutrients (Mn, K, Na, Cu, Mg, Ca, Fe, Zn). The available soil fraction of micronutrients was also evaluated. The nutrients showed different concentration ranges for the natural and the urban sites in the soil (total and available) and in the leaves, that we reported separately. Organic‐matter content and macronutrient concentrations were higher in the natural soils, while the highest leaf N, S, and P concentrations were found at some urban sites. Concentrations of Cu, Na and Zn both in leaves and soil, and Mg and Fe in leaves from the urban sites appeared to be affected by air depositions. Manganese was the only micronutrient to show higher concentrations at the natural than at the urban sites, both in soil and leaves. For this nutrient, in addition, a relationship between leaf and available soil concentrations was found at the natural sites. The ratios between the concentrations of N and each studied nutrient in the leaves highlighted a different nutritional status between the plants from the natural and urban sites.     

Comparative leaf decomposition within the holm oak complex

The decomposition of holm oak leaves was compared using material embracing the genetical range of the holm oak complex. Collection sites were located in Morocco (Quercus rotundifolia), in the French Provence (Q. ilex), and in the French Languedocian coast (Q. ilex × rotundifolia). Leaves (living and senescent) were taken directly on the tree and in the litter at five decomposition stages. The areal weight was used to follow the loss in weight of leaves in the course of their senescence then of their decomposition in order to overcome limitations of the litterbag method. Leaves of Q. rotundifolia had a higher areal weight in their living stage but they lost more weight in the course of decomposition than leaves of Q. ilex. Leaves from hybrid populations had an intermediary behaviour. All three populations of leaves exhibited an increase in weight during senescence. At the white-rot stage (stage V), leaves of every origin reached a similar areal weight. Reasons for the observed resemblance and discrepancies have been discussed in the light of existing knowledge. Our results give additional strength to the separation of Q. ilex and Q. rotundifolia as two distinct species, with possible introgression and hybridization in contact zones.     

Heavy metal accumulation in leaves affects physiological performance and litter quality of Quercus ilex L.

This study aimed to investigate the relationships between leaf functional modifications and heavy metal concentrations of Quercus ilex L., a good bioindicator of air quality. In addition, as metal concentration in litter plays an important role in decomposition and, in turn, in biogeochemical cycles, samples of undecomposed and whole‐leaf litter were analyzed for heavy metals. Leaves and leaf litter of Q. ilex were collected at six sites (roadsides, motorway sites, and urban parks) in Naples (Southern Italy) and characterized for Cd, Cr, Cu, Ni, and Pb concentrations. The investigated functional leaf traits were: leaf area (LA), specific leaf area (SLA), leaf dry‐matter content (LDMC), water content (WC), leaf relative water content (RWC), maximal PSII photochemical efficiency (F_v/F_m, variable fluorescence / maximal fluorescence), and total chlorophyll concentration. The motorways were the most contaminated sites, and Pb was the main responsible source of contamination. The metal contamination caused slight variation of F_v/F_m, suggesting that metals did not significantly alter functionality of the photosynthetic apparatus. On the other hand, it can be supposed that higher leaf deposit can cause an increase of pigment biosynthesis in response to the shading increase caused by dust deposition.     

Physiological responses of Quercus ilex Leaves to Water Stress and Acute Ozone Exposure Under Controlled Conditions

The combined effect of water stress and ozone (O₃) on stomatal O₃ flux, damage to photosynthesis, and detoxification by biogenic volatile organic compounds (BVOC) in Quercus ilex leaves was studied. A 4-weeks O₃ exposure (250 ppb, 4 h per day) caused a reduction of photosynthesis and stomatal conductance, which was fully recovered 1 week after the end of the treatment, in well-watered and water-stressed plants. Measurements of stomatal O₃ flux revealed a low stomatal flux of the pollutant, which became minimal after stomatal closure caused by water stress. An induction of volatile monoterpenes, important compounds in the O₃ scavenging system in Q. ilex, and a burst of lipoxygenase compounds (LOX), which are released as gaseous by-products of membrane peroxidation, was observed after 2–3 weeks of O₃ fumigation. However, these compounds were also released in control leaves that were exposed to ozone only briefly, to determine stomatal O₃ flux. The low stomatal flux that occurred in water stress conditions helped avoiding permanent damage to Q. ilex leaves, although during the O₃ treatment photosynthesis was severely limited by stomatal closure. In well-watered plants, O₃ fumigation caused a noticeable increase of nocturnal stomatal conductance. If confirmed on adult plants under field conditions, this effect can imply larger flux of O₃ at night and possible detrimental effects of O₃ on leaf functions in plants exposed to high nocturnal O₃ levels.     

Photosynthetic physiology of eucalypts along a sub-continental rainfall gradient in northern Australia

Leaf-level photosynthetic parameters of species in the closely related genera Eucalyptus and Corymbia were assessed along a strong rainfall gradient in northern Australia. Both instantaneous gas exchange measurements and leaf carbon isotope discrimination indicated little variation in intercellular CO₂ concentrations during photosynthesis (c_i) in response to a decrease in mean annual precipitation from ∼1700 mm to ∼300 mm. Correlation between stomatal conductance and photosynthetic capacity contributed toward the maintenance of relatively constant c_i among the sampled leaves, when assessed at ambient CO₂ concentration and photon irradiance similar to full sunlight. Leaf mass per area was the most plastic leaf trait along the rainfall gradient, showing a linear increase in response to decreasing mean annual precipitation. The maximum Rubisco carboxylation velocity, V_cmax, expressed on a leaf-area basis, showed a modest increase in response to decreasing rainfall. This modest increase in V_cmax was associated with the strongly expressed increase in leaf mass per area. These results suggest that variation in ecosystem-level gas exchange during the dry season in north-Australian savannas will likely be dominated by changes in leaf area index in response to increasing aridity, rather than by changes in photosynthetic performance per unit leaf area.     

植物叶片特征与光合性能的关系

以相同生境下生长的5种叶片特征(叶色和厚薄等)不同的植物[珊瑚树(Viburnum odoratissimum)、银杏(Ginkgo Biloba)、桑树(Morus alba)、紫叶酢浆草(Oxalis triangularis cv.Purpurea)和紫叶橡皮树(Ficus elasticacv.Decora Burgundyi)]为材料,于晴天选择其植株上东南朝向且生长一致并具代表性的当年生成长叶,采用Li-Cor 6400便携式光合测定系统、调制叶绿素荧光成像系统(IMAGING-PAM M-Series)及双通道PAM-100测量系统(Dual-PAM-100)和常规方法研究了其叶片特征、光合性能及相互间的关系。结果表明,不同植物的叶片特征和光合性能指标均存在显著或极显著差异。比叶干重[35~215 g(DW).m-2]间的差异大于比叶鲜重[0.28~1.04 kg(FW).m-2]。桑树和珊瑚树叶的叶绿体色素含量[叶绿素a(Chla)、叶绿素b(Chlb)、叶绿素总量(Chl)和类胡萝卜素(Xc)]较高,银杏叶和紫叶橡皮树叶居中,紫叶酢浆草叶最低;紫叶酢浆草叶的花青素(Ant)含量最高[0.122 mg.g-1(FW)和0.488 mg.g-1(DW)],其他植物较低且差异较小;紫叶酢浆草叶的Chla/Chlb(6.27)、桑树的Chl/Xc(9.97)、桑树叶的Chl/Ant(43.81)和珊瑚树叶的Xc/Ant(7.17)最高,紫叶酢浆草叶的Chl/Ant(0.49)和Xc/Ant(2.46)最低。气孔导度、蒸腾速率、胞间CO2浓度和净光合速率(Pn)均为桑树>银杏>紫叶酢浆草>珊瑚树>紫叶橡皮树。桑树和珊瑚树叶的PSII实际光合效率[Y(II)]最高,但PS II处非调节性能量耗散的量子产量也最高;银杏Y(II)叶较低,但能抵御强光的照射。桑树、紫色酢浆草和紫色橡皮树叶的PSI光合效率[Y(I)]极高,但桑树和紫色橡皮树PSI的光保护较弱,紫色酢浆草则很强。相关分析显示,Ant和Xc对强光下Pn无显著影响,Pn受气孔特征和叶绿素含量的正调控,Y(II)依赖于叶绿体色素含量(尤其是Chla),Y(I)与Chl/Xc呈正向关系;气孔开放和叶绿素含量可负调控光合机构的光保护和正调控光损伤,Xc则相反。     

Nutritional Status of Mediterranean Trees Growing in a Contaminated and Remediated Area

Soil contamination may contribute to forest decline, by altering nutrient cycling and acquisition by plants. This may hamper the establishment of a woody plant cover in contaminated areas, thus limiting the success of a restoration program. We studied the nutritional status of planted saplings of Holm oak (Quercus ilex subsp. ballota (Desf.) Samp.), white poplar (Populus alba L.), and wild olive tree (Olea europaea var. sylvestris Brot.) in the Guadiamar Green Corridor (SW Spain) and compared it with established adult trees. Soils in this area were affected by a mine-spill in 1998 and a subsequent restoration program. The spill resulted in soil acidification, due to pyrite oxidation, and deposited high concentrations of some trace elements. In some sites, we detected a phosphorus deficiency in the leaves of Q. ilex and O. europaea saplings, as indicated by a high N:P ratio (>16). For O. europaea, soil contamination explained 40% of the variability in leaf P and was negatively related to chlorophyll content. Soil pH was a significant factor predicting the variability of several nutrients, including Mg, P, and S. The uptake of Mg and S by P. alba was greater in acidic soils. The monitoring of soil pH is recommended since long-term effects of soil acidification may negatively affect the nutritional status of the trees.     

Feeding preferences of native terrestrial isopod species (Oniscoidea,Isopoda) for native and introduced leaf litter

Due to current predictions for Central Europe that forecast higher frequencies of hot and dry summers, Mediterranean drought-tolerant oak species are being evaluated as future forest trees for German forest sites that are becoming increasingly damaged by water deficit. As a result of planting foreign tree species, the leaf litter composition and thus the food resources of native saprophagous macroarthropods will change, possibly altering primary decomposition processes. Therefore, experiments concerning the acceptance and palatability of introduced versus native litter for native isopods were undertaken. Consumption rates of four native isopod species (Porcellio scaber, Oniscus asellus, Trachelipus rathkii, Trachelipus ratzeburgii) were investigated in laboratory choice tests with introduced (Quercus pubescens, Quercus frainetto, Quercus ilex) and comparable native (Fagus sylvatica, Quercus robur) leaf litter. Litter was characterized by measurement of C/N-ratios and lignin content. Although species-specific preferences of isopods could be observed in the experiments, Mediterranean oak litter was consumed by all investigated species. Furthermore, two isopod species even preferred the leaf litter of the introduced Q. ilex. Compared to native beech or oak litter, litter from these introduced tree species thus apparently do not negatively influence the consumption rates of terrestrial isopods. Possible reasons for the determined preferences are discussed.     

Effect of crude oil on gas exchange functions of Juncus roemerianus and Spartina alterniflora

The effect of crude oil on gas exchange functions of Juncus roemerianus and Spartina alterniflora, two important U.S. Gulf Coast plant species, were examined. Plants were exposed to petroleum hydrocarbons (Mexican Sour type) mixed with water at 4.4 mL L^?1 (2 L m^?2). Coating entire leaf with oil resulted in cessation of photosynthetic activity. Partial leaf exposure to oil resulted in net photosynthesis decrease in both species shortly after exposure. Net photosynthesis remained within 71 and 94% of control plants in J. roemerianus during the first four weeks of the experiment. In S. alterniflora, photosynthetic rates averaged between 53 to 80% of control plants during the same period. Four weeks following the partial oiling, net photosynthesis began to improve in both species. Partial oil coverage of leaves of both species resulted in reduction in normal photosynthetic activity with no lethal effects. By the end of the laboratory study, there was no significant reduction in production of new shoots or the overall growth of either species.     

Microbial activity and quality changes during decomposition of Quercus ilex leaf litter in three Mediterranean woods

Changes in enzyme activities during litter decomposition provide diagnostic information on the dynamics of decay and functional microbial succession. Here we report a comparative study of enzyme activities involved in the breakdown of major plant components and of other key parameters (microbial respiration, fungal biomass, N, lignin and cellulose contents) in homogeneous leaf litter of Quercus ilex L. incubated in three evergreen oak woods in Southern Italy (Campania), differing for chemical and physical soil characteristics and microclimatic conditions. The results showed that the litter mass loss rates were similar in the three wood sites. Independently of the incubation sites, cellulase, xylanase and peroxydase activities showed seasonal variations with maximum and minimum levels in wet and dry periods, respectively, and this pattern closely matched microbial respiration. Activities of α- and β-amylase, instead, were high at the beginning of incubation and quickly decreased with decomposition progress because their substrate was rapidly depleted. Laccase activity, in contrast, was low at the beginning of incubation but after 6 months it increased significantly. The increase of laccase activity was correlated to an increase in fungal biomass, probably reflecting a major shift in the litter microbial community. As concerns quality changes, N and lignin content did not significantly change during decay. The cellulosic component started being degraded after about 6 months in the litter incubated in two of the three wood sites and from the start of decomposition in the third site. Apart from minor differences in the levels of certain enzyme activities, the data showed that the functional microbial succession involved in the decomposition of Q. ilex leaf litter did not change appreciably in response to differences in soil and microclimatic conditions in the incubation sites.     

A gas-exchange study of the differential response of Quercus species to long-term fumigations with a gradient of sulphur dioxide

Young oak plants (Quercus pubescens Willd. and Q. cerris L.) were exposed for 23 weeks to a gradient of sulphur dioxide concentrations (28, 61, 93 ppb in vol., compared with charcoal filtered-air ventilated controls) in fumigation chambers. Foliar gas exchange was analyzed by an IRGA methodology after 11 weeks and chlorophyll was assessed in a non-destructive way. At the end, foliar biomass produced during the experimental period was determined and its total sulphur and carbohydrate content analyzed. Visible foliar injury, as well as reduction in chlorophyll content was not observed. Carbon dioxide assimilation was linearly depressed by sulphur dioxide in both the species, with a maximum depression of 25% in Q. pubescens and 44% in Q. cerris. Stomatal conductance and transpiration were negatively affected only in Q. pubescens, with a linear trend. The two species showed a similar behaviour in water use efficiency, this parameter being reduced in a linear fashion. The intracellular/ambient carbon dioxide concentration ratio was affected in a differential way: while in Q. pubescens no alteration was evident, a linear increase was shown by Q. cerris. Total foliar sulphur content was dramatically increased in both the species. Average leaf area was unaffected in both the species. Reduction in foliar dry weight was only observed in Q. cerris (?30% at the highest sulphur dioxide concentration). We speculate that in Q. pubescens photosynthetic limitations are mainly of stomatal nature, and in Q. cerris the major constraints are probably associated with mesophyll disturbances. Foliar starch content was linearly increased by the pollutant.     

氮素对玉米灌浆期叶片光合性能的影响

以玉米自交系齐319(Q319)为材料,采用单株盆栽种植方式,借助叶绿素荧光快速诱导动力学曲线和820 nm光吸收曲线,研究了氮素对玉米灌浆期叶片光合性能的影响。2年研究结果表明,在本试验条件下,氮素对Q319灌浆期叶片叶绿素含量无明显提高作用,但其净光合速率(Pn)和单株干物质积累量、子粒产量显著增加。JIP-test分析表明,氮素显著提高了叶片光系统Ⅱ(PSⅡ)反应中心电子供体侧和受体侧性能;显著提高了Q319 PSⅡ反应中心电子受体侧之后的电子传递链性能,增强了电子由PSⅡ向PSⅠ的分配,从而显著地提高了PSⅡ与PSⅠ之间的协调性。可以认为,施氮后灌浆期叶片叶绿素含量的变化不是Pn提高的主要原因,而两个光系统性能的改善及二者间协调性的提高增强了光合电子传递链的性能是灌浆期Pn升高与成熟期产量增加的主要原因。     

水淹胁迫下绣球光合响应机制的研究

为探究绣球对水淹胁迫的光合响应及适应机制,以盆栽的绣球品种无尽夏新娘和银边为试验材料,利用浸盆法进行水淹处理30 d,测定其比叶质量、光合参数和叶绿素荧光参数。结果表明,水淹胁迫后,2个绣球品种的暗呼吸速率(Rd)和光补偿点(LCP)均有所提高,而净光合速率(Pn)、光饱和点(LSP)、胞间CO₂浓度(Ci)、气孔导度(Gs)和蒸腾速率(Tr)均下降;表明水淹胁迫导致绣球叶片气孔关闭,光合能力降低,呼吸能耗加强,不利于有机物积累;无尽夏新娘的表观量子效率、光化学效率和电子传递速率均降低,尤其是电子传递速率降低超过69%,表明非气孔限制因素是其Pn降低的主要原因;但无尽夏新娘比叶质量升高约44%,提高了资源利用效率,且其光化学反应耗能降低69%,将叶片吸收光能向热耗散等光系统Ⅱ(PSⅡ)调节性能量耗散途径分配的比例提高,削弱过剩激发能在反应中心的积累,从而保护光合机构免受破坏;银边的电子传递速率有所降低,约31.5%,但其表观量子效率和光化学效率均无明显变化,说明其PSⅡ反应中心未受损,Pn降低主要是气孔限制因素,且其叶片吸收光能主要向非光化学反应耗散途径分配,升高约26.5%,这可能是其通过PSⅡ循环电子传递消耗了过剩光能,从而保证了光合机构的正常运行。本研究结果为绣球的园林应用提供了新思路。     

有机肥和化肥对烟叶气体交换、叶绿素荧光特性及叶绿体超微结构的影响

【目的】本文以烤烟K326为材料,探讨了在不同叶龄时期有机肥与化肥在烟叶气体交换参数、叶绿素荧光特性、叶绿素含量及叶绿体超微结构等方面的差异,以期从光能利用(宏观)及叶绿体超微结构(微观)方面,揭示两种肥料配比对烟叶光合作用的影响机制,同时为探索烟叶高产优质栽培模式提供理论依据。【方法】以蛭石为栽培基质进行盆栽试验。设施用烤烟专用有机肥(N∶P2O5∶K2O为9∶9∶10,有机质≥70%,中、微量元素≥12%)和施用普通尿素两个处理。烟草为工厂化无毒育秧苗,叶龄(叶龄从叶片长约2 cm时算起)15天、30天、45天、60天和75天取样或测定自上而下第6~8片叶。用Li-6400(美国)便携式光合仪测定烟叶的净光合速率,蒸腾作用与气孔导度。使用M系列调制叶绿素荧光成像系统Maxi-Imaging-PAM(德国)测定叶绿素荧光参数。用C-7000透射电子显微镜观测叶绿体超微结构并拍照,用软件Auto CAD 2004计算淀粉颗粒在叶绿体中所占的相对面积比Ra,叶绿体基粒片层的统计方法据Goodenough等改进的Teichler-Zallen法。【结果】有机肥对烟叶叶绿素含量及光合速率的影响显著,在叶龄60天时,其叶绿素含量比普通化肥高136.1%;在叶龄75天时,其烟叶净光合速率、气孔导度及蒸腾速率分别比普通化肥处理高135.3%、84.5%和51.3%,叶绿素荧光参数Y[Ⅱ]和q L分别比普通化肥处理高22.2%和39.5%,Fv/Fm在叶龄60天时比普通化肥处理高18.7%,而NPQ值在叶龄45天时普通化肥比有机肥处理高23.3%。叶绿体内孕育的淀粉粒随叶龄的增加而逐渐膨大,期间伴随着淀粉粒在叶绿体中所占的面积比例(Ra值)越来越大,两处理Ra值差异明显,尤其是在叶龄45天时,化肥栽培下的烟叶Ra值比有机肥栽培高31.8%。有机肥处理的叶绿体呈梭形,长宽比大,而普通化肥种植的叶绿体形态近圆形,长宽比小。【结论】施用有机肥可显著提高烟叶叶绿素含量及光合速率,且随叶龄的增加,有机肥的作用效果日趋明显。叶绿素荧光参数的差异表明,增施生物有机肥可延缓烟株衰老、提高烟叶光能利用效率。两种施肥方式下,淀粉颗粒Ra值的差异不能说明施用化肥可提高烟叶合成淀粉的能力。与普通化肥处理下的烟叶相比,有机肥可显著提高叶绿体基粒垛叠数大于10的片层占基粒垛叠片层总数的百分比。     

Lead Accumulation in Quercus Nigra and Q. Velutina near Smelting Facilities in Alabama,U.S.A.

Lead is very toxic and if ingested cancause severe health problems to both animals andhumans. To determine if lead accumulation in treescould provide a direct pathway to enter the foodchain, oaks (Q. nigra or Q. velutina)growing near two lead smelting facilities in Alabama,U.S.A., were analyzed for lead in acorns, leaves and treecores. A relatively pristine site was used as acontrol. Lead was not detected in acorns collected atany site, and was only found in tree cores from thesites near smelters. Significant increases in treecore lead from 1975–1995 were detected at the activesmelter site. Results were different from the inactivesmelter site; lead increased in tree cores until thesmelter ceased operation, then decreased afterclosing. Soil lead decreased linearly with distancefrom both smelters. In addition, a significantpositive relationship was observed between leaf andsoil lead at the site with the active smelter, andmay be the result of both translocation via treeroots, and foliar absorption of deposited lead ionsinto the leaf structure.     

Salinity and Defoliation Effects on Soybean Growth

An experiment was conducted to determine if salinity stress alters the response and tolerance of soybean to defoliation. Four soybean [Glycine max(L.) Merr.] cultivars (‘Tachiutaka,’ ‘Tousan 69,’ ‘Dare’ and ‘Enrei’) in a growth chamber were exposed to two salinity treatments (0 and 40 mM NaCl) and two defoliation treatments (with and without defoliation). The interactive effects of salinity stress and defoliation on growth rate, leaf expansion, photosynthetic gas exchange, and sodium (Na⁺) accumulation were determined. The decrease in growth rate resulting from defoliation was more pronounced in plants grown under salinity stress than in those grown without the stress. Without salinity stress, defoliated plants of all four cultivars had leaf-expansion similar rates to those of the undefoliated ones, but the photosynthetic rates of their remaining leaves were higher than those of undefoliated plants. However, with salinity stress, defoliated ‘Tachiutaka’ and ‘Tousa 69’ had lower leaf expansion and photosynthetic rates than undefoliated plants. For cultivars ‘Dare’ and ‘Enrei,’ the defoliated plants had leaf-expansion rates similar to undefoliated ones, but the photosynthetic rate of the remaining leaves did not increase. Except for cultivar ‘Dare,’ defoliated plants grown under salinity stress had higher Na⁺ accumulation in leaves than undefoliated ones, and this result may be related to slow leaf expansion and photosynthesis. Salinity stress negatively affects soybean response and tolerance of defoliation, and the effects varied according to the salt tolerance of the cultivar.     

Modification of ozone effects on photosynthetic capacity of winter wheat (Triticum aestivum L. CV. perlo) at different levels of water availability

Attached leaves were used for the determination of the photochemical capacity by means of a portable fluorimeter. Repeated fluorescence measurements showed the negative effects of ozone on photochemical capacity and these negative effects increased with increasing ozone doses. But impairments of photochemical capacity were smallest if severe water stress co-occurred with ozone exposures. The upper leaf sides experienced more reduction of photochemical capacity in well-watered plants than the lower leaf sides, possibly by the additional effect of light stress on the upper leaf sides. In diurnal studies, a decline of F _v/F _m was observed at noontime and a recovery at evening in both control and ozone-fumigated leaves at two extreme water capacities (w.c.) (75% and 35% of w.c.). The extent of depression and recovery of F _v/F _m was not significantly varying. The oscillations of F _v/F _m could be due to short-term disturbances in the photosynthetic capacity, due to oxidative stress.     

Physiological Responses of <Emphasis Type="Italic">Rosa rubiginosa</Emphasis> to Saline Environment

The aim of this work was to analyse the response of Rosa rubiginosa to salinity induced by different concentrations of sodium chloride and calcium chloride (0, 25, 50, 100, 150 and 200 mM). Besides salt accumulation and pH changes, other parameters were investigated including photosynthetic activity, leaf water content, the dynamics of necrosis and chlorosis appearance and leaf drying. The study was complemented with microscopic analysis of changes in leaf anatomy. R. rubiginosa was more sensitive to the salinity induced by calcium chloride than by sodium chloride. Plant response to salinity differed depending of the salt concentration. These differences were manifested by higher dynamics of necrosis and chlorosis appearance and leaf drying. CaCl₂ showed greater inhibition of the photosynthetic apparatus and photosynthetic activity. Treatment with CaCl₂ caused more visible deformation of palisade cells, reduction in their density and overall reduction in leaf thickness. The study demonstrated higher accumulation of CaCl₂ in the soil, and thus greater limitations in water availability resulting in reduced leaf water content and quicker drying of leaves as compared with NaCl-treated plants.     

外源硫化氢对盐胁迫下加工番茄幼苗光合参数及叶绿素荧光特性的影响

为探究外源硫化氢(H_2S)对盐胁迫下加工番茄幼苗光合作用和光合荧光参数的影响,以耐盐性不同的2个加工番茄KT-7(耐盐性强)和KT-32(耐盐性弱)为材料,采用分光光度法、CIRAS-3型光合仪和Imaging-PAM调制荧光成像系统分别测定光合色素含量、光合参数和叶绿素荧光参数。结果表明,外源H_2S提高了盐胁迫下加工番茄幼苗的生长及叶绿素a、叶绿素b、胡萝卜素含量、净光合速率(P_n)、气孔导度(G_s)、叶片蒸腾速率(Tr)、PSⅡ最大光化学效率(F_v/F_m)和PSⅡ实际光化学效率(ΦPSⅡ);降低了胞间CO_2浓度(Ci)、PSⅡ调节性能量耗散的量子产额[Y(NPQ)]和非光化学猝灭系数(NPQ);而PSⅡ非调节性能量耗散的量子产额[Y(NO)]稳定在较低水平。此外,外源H_2S对KT-32的缓解效应强于KT-7。综上所述,外源H_2S通过提高加工番茄幼苗叶片的光合色素量和光合电子传递效率,有效地缓解盐胁迫对加工番茄叶片PSⅡ的伤害。本研究结果为探究外源H_2S增强加工番茄耐盐性研究提供了科学依据。