Effects of Nitrogen Application on Chlorophyll Fluorescence Parameters and Leaf Gas Exchange in Naked Oat

Naked oat（Avena nuda L.） was originated from China,where soil nitrogen（N） is low availability.The responses of chlorophyll（Chl.） fluorescence parameters and leaf gas exchange to N application were analysed in this study.After the N application rate ranged from 60 to 120 kg ha-1,variable fluorescence（F v）,the maximal fluorescence（F m）,the maximal photochemical efficiency（F v /F m）,quantum yield（Φ PS II） of the photosynthetic system II（PS II）,electron transport rate（ETR）,and photochemical quenching coefficient（qP） increased with N application level,however,non-photochemical quenching coefficient（qN） decreased.Moreover,there was no difference in initial fluorescence（F o） with further more N enhancement.The maximum net photosynthetic rate（P max）,apparent dark respiration rate（R d） and light saturation point（LSP） were improved with 40-56 kg N ha-1as basal fertilizer and 24-40 kg N ha-1as top dressing fertilizer applied at jointing stage.Initial quantum yield（α） was decreased with 24 kg N ha-1as basal fertilizer and 56 kg N ha-1as top dressing fertilizer.Flag-leaf net photosynthetic rate（P n） was significantly enhanced at the jointing and heading stages with 40-56 kg N ha-1as basal fertilizer; in addition,increased at grain filling stage of naked oat with 40-56 kg N ha-1as top dressing fertilizer.90 kg N ha-1（50-70% as basal fertilizer and 30-50% as top dressing fertilizer） application is recommended to alleviate photodamage of photosystem and improve the photosynthetic rate in naked oat.

Effects of soil drought stress on photosynthetic gas exchange traits and chlorophyll fluorescence in Forsythia suspensa

To clarify the changes in plant photosynthesis and mechanisms underlying those responses to gradually increasing soil drought stress and reveal quantitative relationships between photosynthesis and soil moisture,soil water conditions were controlled in greenhouse pot experiments using 2-year-old seedlings of Forsythia suspensa（Thunb.） Vahl. Photosynthetic gas exchange and chlorophyll fluorescence variables were measured and analyzed under 13 gradients of soil water content. Net photosynthetic rate（PN）, stomatal conductance（gs）, and water-use efficiency（WUE） in the seedlings exhibited a clear threshold response to the relative soil water content（RSWC）. The highest PNand WUEoccurred at RSWCof51.84 and 64.10%, respectively. Both PNand WUEwere higher than the average levels at 39.79% B RSWCB 73.04%. When RSWCdecreased from 51.84 to 37.52%,PN, gs, and the intercellular CO2 concentration（Ci）markedly decreased with increasing drought stress; the corresponding stomatal limitation（Ls） substantially increased, and nonphotochemical quenching（NPQ） also tended to increase, indicating that within this range of soil water content, excessive excitation energy was dispersed from photosystem II（PSII） in the form of heat, and the reduction in PNwas primarily due to stomatal limitation.While RSWCdecreased below 37.52%, there were significant decreases in the maximal quantum yield of PSII photochemistry（Fv/Fm） and the effective quantum yield of PSII photochemistry（UPSII）, photochemical quenching（qP）, and NPQ; in contrast, minimal fluorescence yield of the dark-adapted state（F0） increased markedly. Thus,the major limiting factor for the PNreduction changed to a nonstomatal limitation due to PSII damage. Therefore, an RSWCof 37.52% is the maximum allowable water deficit for the normal growth of seedlings of F. suspensa, and a water content lower than this level should be avoided in field soil water management. Water contents should be maintained in the range of 39.79% B RSWCB 73.04% to ensure normal function of the photosynthetic apparatus and high levels of photosynthesis and efficiency in F.suspensa.

Chlorophyll Fluorescence, Photosynthetic and Morphological Characteristics of Waterlogged Sesame Seedlings

Two sesame accessions, ZZM2541 and Ezhi-2, with different tolerance to waterlogging were selected, and the seedlings at the 4-true leaf stage were treated by waterlogging for 48 h. Growth parameters were evaluated 1 d before the beginning of waterlogging and on the 3^(rd)day after the removal of waterlogging(DARW). Morphological characteristics of root and chlorophyll fuorescence were measured on the 3^(rd)DARW and leaf gas exchange was measured on the zero, 3^(rd)and 15^(th) DARW. Results showed that sesame accessions ZZM2541 and Ezhi-2 responded to waterlogging in considerably different performance. The stress induced leaf chlorosis and abscission and slowed growth of plant height in both accessions, but symptom occurred seriously in the susceptive Ezhi-2. In the more tolerant ZZM2541, plentiful of adventitious roots formed above the level.All of the average values of maximum fuorescence yield(F_m), quantum efficiency of open PSII centres(F_v/F_m), initial fluorescence(F_v/F_0) and chlorophyll content(Chl) decreased at the 4-true leaf stage in both accessions after suffering to the stress.The decreases of F_m, F_v/F_0 and Chl were more pronounced in Ezhi-2 than in ZZM2541. Less reductions of mean photosynthetic rate(Pn), transpiration rate(Tr), and stomatal conductance(gs) were observed in the leaves of waterlogged ZZM2541 than in waterlogged Ezhi-2(compared to controls), and the leaves of Ezhi-2 showed a higher water use efficiency(WUE) after the removal of waterlogging. Based on the results, it was concluded that the tolerance to waterlogging of ZZM2541 appears to depend on a combination of photosynthetic characteristics responses and morphological adaption.

Effects of extreme soil water stress on photosynthetic efficiency and water consumption characteristics of Tamarix chinensis in China's Yellow River Delta

Soil moisture is a major limiting factor for plant growth on shell ridge islands in the Yellow River Delta. However, it is difficult to carry out situ experiment to study dominant plant photosynthesis physiological on the shell ridge islands under extreme soil water stress. To evaluate the adaptability of plants to light and moisture variations under extreme soil moisture conditions present on these islands, we measured photosynthetic gas exchange process, chlorophyll fluorescence, and stem sap flow variables for 3-year-old trees of Tamarix chinensis Lour, a restoration species on these islands, subjected to three types of soil water levels： waterlogging stress （WS）, alternating dry-wet （WD）, and severe drought stress （SS） to inform decisions on its planting and management on shell ridge islands. Gas exchange, chlorophyll fluorescence, and stem sap flow in T. chinensis were then measured. Net photosynthetic rate （PN）, transpiration rate （E）, and water use efficiency （WUE） were similar under WS and alternating dry-wet conditions, but their mean E and WUE differed significantly （P 〈 0.05）. Under SS, the PN, E and WErE of T. chinensis leaves varied slightly, and mean PN, E and WUE were all low. Apparent quantum efficiency （AQY）, light compensation point （LCP）, light saturation point （LSP）, and maximum net photosynthetic rate （PNmax） of leaves were not significantly different （P 〉 0.05） under WS and dry-wet conditions; however, under extreme drought stress, compared with the dry-wet conditions, LCP was higher, Lsp was lower, and AQy and PNmax were both at the lowest level. Therefore, drought stress weakened light adaptability of leaves, and the efficiency of light transformation was poorer. （3） Maximum photochemical efficiency （Fv/Fm） and the actual photochemical efficiency （ΦPSII） were similar under waterlogged stress and dry-wet conditions, indicating a similar healthy photosynthetic apparatus and photosynthetic reaction cen- ter activity, respectively. Under SS, Fv/Fm was 0.631, and the coefficient of non-photochemical quenching （NpQ） was 0.814, which indicated that while the photosynthetic mechanism was damaged, the absorbed light energy was mainly dissipated in the form of heat, and the potential photosynthetic productivity was significantly reduced. The daily cumulants of sap flow of T. chinensis under drywet alternation and severe drought stress were. 22.25 and 63.97% higher, respectively, than under waterlogging stress. Daily changes in sap flow velocity for T. chinensis differed under the three soil water levels. Stem sap flow was weak at night under severe drought stress. Under drywet alternation, daytime average stem sap flow velocity was the highest, and night stem flow accounted for 10.26% of the day cumulants, while under waterlogged stress, the average nightly stem flow velocity was the highest, accounting for 31.82% of the day cumulants. These results provide important information for regional vegetation restoration and ecological reconstruction.

Effects of drought stress on the photosynthetic physiological parameters of Populus 3 euramericana ‘‘Neva''

Populus 9 euramericana ‘‘Neva'' is the main poplar species in China, where drought stress is becoming extremely urgent. We carried out this research to study the effects of drought stress on the photosynthesis of Populus 9 euramericana ‘‘Neva''. Drought stress was induced by 58–62%(light), 48–52%(moderate), and 38–42%(severe) relative soil moisture content(RSMC). The effects of drought stress on photosynthetic rate, chlorophyll fluorescence parameters, and other related physiological parameters were investigated during treatment. Net photosynthetic rate(PN), and stomatal conductance decreased significantly and intercellular CO_2 concentration initially increased and then declined, whereas the stomatal limitation factors showed opposite trends in the light under moderate drought stress. Photosystem II(PSII) maximum photochemical efficiency, actual photochemical efficiency,and photochemical quenching decreased gradually under drought stress, whereas nonphotochemical quenching initially increased and then declined. Superoxide dismutase,peroxidase, and catalase activities initially increased and then decreased as RSMC was reduced, whereas malondialdehyde(MDA) content and relative electric conductivity(REC) increased gradually. These results suggest that stomatal factors accounted for the decline in PNunder light and moderate drought stress, whereas leaf PNdecreased mainly due to non-stomatal factors under severe drought stress. PSII was damaged; thus, photosynthetic electron transfer was restricted, indicating that heat dissipation is important for the light protection mechanism of plants.Antioxidant enzymes increased at the beginning of treatment, and the increased MDA and REC led to cell membrane damage. These results suggest that poplar seedlings stabilized their photosynthetic apparatus by reducing the light trapping ability under light and moderate drought stress conditions. This helped dissipate heat and enhance antioxidant enzyme activity. Stomatal factors accounted for the decline in P_N, whereas damage to PSII and antioxidant enzymes under severe drought stress suggested that the decline in P_N was caused by non-stomatal restrictive factors.

Photosynthesis of Digitaria ciliaris during repeated soil drought and rewatering

The ability of psammophyte photosynthesis to withstand and recover from severe droughts is crucial for vegetation sta- bility in semi-arid sandy lands. The responses of gas exchange and chlorophyll fluorescence of an annual grass, Digitaria ciliaris, were measured through three soil drought and rewatering cycles. Results showed that the net photosynthesis rate （P,） decreased by 92%, 95%, and 63% at end of the three drought periods, respectively, water use efficiency （WUE） decreased by 67%, 54%, and 48%, while the constant intercellular CO2 concentration （Ci） increased by 1.08, 0.88, and 0.45 times. During those three cycles, the trapping probability with no dark adaptation （Fv＇/Fm＇） decreased by 55%, 51%, and 9%, the electron transport per cross section （ET0＇/CS0＇） decreased by 63%0, 42%, and 18%, and the dissipation per cross section （DI0＇/CS0＇） increased by 97%, 96%, and 21%. These results indicated that D. ciliaris was subjected to photoinhi- bition and some non-stomatal limitation of photosynthesis under drought. However, after four days of rewatering, its photosynthetic characteristics were restored to control values. This capability to recover from drought may contribute to making the plant＇s use of water as efficient as possible. Furthermore, the photosynthesis decreased more slowly in the subsequent drought cycles than in the first cycle, allowing D. ciliaris to enhance its future drought tolerance after drought hardening. Thus, it acclimatizes itself to repeated soil drought.

A Study on Photosynthetic Physiological Characteristics of Six Rare and Endangered Species

The parameters of gas exchange and chlorophyl fluorescence in leaves of six rare and endangered species Neolitsea sericea, Cinnamomum japonicum var. cheni , Sinojackia microcarpa, Discocleidion glabrum var. trichocarpum, Parrotia sub-aequalis, Cercidiphyl um japonicum were measured in fields. The results showed that there were significant differences in photosynthetic capacity, intrinsic water use effi-ciency （WUEi ）, the efficiency of primary conversion of light energy of PSⅡ and its potential activity, the quantum yield of PSⅡ electron transport, and the potential ca-pacity of heat dissipation among the six species. However, there was no significant difference in WUE. The highest values of net photosynthetic rate （Pn）, transpiration rate （Tr） and stomatal conductance （gs） occurred in D. glabrum var. trichocarpum and the lowest in S. microcarpa. On the contrary, D. glabrum var. trichocarpum had the lowest WUE, intrinsic water use efficiency （WUEi ） and S. microcarpa had the highest. The results indicated that D. glabrum var. trichocarpum had higher photo-synthetic capacity and poorer WUE, while S. microcarpa had lower photosynthetic capacity and greater WUE. Furthermore, the mean values of maximal fluorescence （Fm）, potential efficiency of primary conversion of light energy of PSⅡ （Fv/Fm）,ΦPSⅡ, actual efficiency of primary conversion of light energy of PSⅡ （F′v/F′m） and non-photochemical quenching coefficient （NPQ） were the highest in S. micro-carpa, indicating that its PSⅡ had higher capacity of heat dissipation and could prevent photosynthetic apparatus from damage by excessive light energy. Correlation analysis showed that there were significant correlations among photosynthetic physi-ological parameters. However, the initial fluorescence （Fo） was not significantly cor-related with any other parameters. This study also revealed the extremely significant positive correlations between Pn and Tr, gs, apparent quantum yield （AQY）, be-tween Tr and gs, between light saturation point （LSP） and AQY, between Fv/Fm and Fm, between ΦPSⅡ and photochemical quenching coefficient （qp）, between Tr, gs and LSP, AQY. However, WUEi was significantly negatively correlated with Tr, gs, Pn, LSP and AQY.

Adaptability and recovery capability of two maize inbred-line foundation genotypes, following treatment with progressive water-deficit stress and stress recovery

Two maize inbred lines, the foundation genotype Y478 and its derived line Z58, are widely used to breed novel maize cultivars in China, but little is known about which traits confer Z58 with superior drought tolerance and yield. In the present study, responses in growth traits, photosynthetic parameters, chlorophyll fluorescence and leaf micromorphological characteristics were evaluated in Y478 and Z58 subjected to water-deficit stress induced by PEG 6000. The derived line Z58 showed greater drought tolerance than Y478, which was associated with higher leaf relative water content (RWC), root efficiency, and strong growth recovery. Z58 showed a higher stomatal density and stomatal area under the non-stressed condition;in these traits, both genotypes showed a similar decreasing trend with increased severity of water-deficit stress. In addition, the stomatal size of Y478 declined significantly. These micromorphological differences between the two lines were consistent with changes in physiological parameters, which may contribute to the enhanced capability for growth recovery in Z58. A non-linear response of Fv/Fm to leaf RWC was observed, and Fv/Fm decreased rapidly with a further gradual decline of leaf RWC. The relationship between other chlorophyll fluorescence parameters (photochemical quenching and electron transport rate) and RWC is also discussed.

Photosynthetic performance of Setaria viridis to soil drought and rewatering alternations

The ability of psammophyte(a plant that grows in sand or sandy soil) to withstand and recover from severe droughts is crucial for desertification control and restoration of degraded vegetation in semi-arid sandy land in northern China.Responses of the photo-synthetic gas exchange and chlorophyll fluorescence of an annual(Setaria viridis) were measured through three cycles of soil drying and rewatering.Results showed that the net photosynthesis rate(Pn) decreased by 95 percent,91 percent,and 61 percent at end of three drought periods;the stomatal conductance(gs) decreased by 72 percent,73 percent,and 53 percent;the transpiration rate(Tr) decreased by 70 percent,69 percent,and 37 percent;and water-use efficiency(WUE) decreased by 83 percent,69 percent,and 38 percent.At the same time,the trapping probability with no dark adaptation(FV'/FM') decreased by 70 percent,12 percent,and 10 percent,while the electron transport per cross-section(ET0'/CS'0) decreased by 80 percent,45 percent,and 13 percent.The intercellular CO2(Ci) increased by 1.77,1.02,and 0.66 times,and the dissipation per cross-section(DI0'/CS0') increased by 98 percent,28 percent,and 22 percent.These results indicated that S.viridis was subjected to photoinhibition and some nonstomatal limitation of photosynthesis under drought.However,the above photosynthetic characteristics were restored to control values after three or four days of rewatering.The capability to recover from drought may contribute to the plant's use of water as efficiently as possible.Furthermore,during the subsequent drought spells,suppression of Pn,gs,Tr,FV'/FM',and ET0'/CS0' decreased or slowed down following the drying and rewatering alternations,especially in the third drought spell.

9个山茶品种对高温胁迫的光合生理响应及其耐热性综合评价

【目的】山茶的花型和花色丰富、花期长,其耐热性日益受到关注,筛选合适的评价方法和指标可为山茶属植物耐热性鉴定、种质发掘和新品种选育提供理论依据。【方法】以耐热性较强的单体红山茶和‘串花瀑布’为对照,7个自育束花茶花新品种为试验对象,采用瓶插方法,在短期(5 h)和长期(7 d)高温(42℃/35℃)处理后,考察各品种形态及光合生理标指标的变化,并综合评价其耐热性。【结果】(1)‘垂枝粉玉’和‘串花瀑布’在高温胁迫下叶绿素含量、类胡萝卜素含量、叶绿素a/b、净光合速率(Pn)和气孔导度(Gs)均上升,PSⅡ最大光化学效率(F_(v)/F_(m))、PSⅡ潜在活性(F_(v)/F_(o))和电子传递速率(ETR)维持在较高水平,且长期高温胁迫后均未出现热害。‘金叶粉玉’、‘上植华章’和‘玫瑰春’在高温胁迫下Pn和Gs均显著降低,而Ci升高,‘金叶粉玉’和‘上植华章’的F_(v)/F_(m)、F_(v)/F_(o)和ETR均大幅降低,且长期高温胁迫后出现较严重热害或死亡。(2)通过主成分分析将15个单项指标换算成4个独立的综合指标,累计贡献率可达90%;短期高温时以叶绿素含量、类胡萝卜素含量、叶黄素含量的综合权重值较高,长期高温时以叶绿素a/b、F_(v)/F_(m)、光化学淬灭系数(qP)、非光化学淬灭系数(qN)的综合权重值较高。【结论】新品种‘垂枝粉玉’耐热较强,‘上植月光曲’、‘上植欢乐颂’和‘玫玉’中等耐热,‘玫瑰春’、‘上植华章’和‘金叶粉玉’耐热性较弱;叶绿素、类胡萝卜素、叶黄素含量可作为山茶短期耐热性考察指标,而叶绿素a/b、F_(v)/F_(m)、qP、qN可作为山茶长期耐热性的考察指标。

油莎豆种质资源光合特性分析

为鉴选油莎豆高光效优异种质,以40份油莎豆种质资源为试验材料,测定油莎豆叶片气体交换参数、叶绿素荧光参数以及叶绿素含量等光合参数,利用相关性分析和主成分分析等多种统计学方法,综合评价与分析油莎豆种质资源光合特性。结果表明,20个光合参数的变异系数为1.23%~48.51%,总性能指数(PI_(total),光系统Ⅱ、光系统Ⅰ和系统间电子传递链的整体功能活性)的变异系数最大。PI_(total)与F_(v)/F_(m)(t=0时,原初光化学反应最大量子产率)、S_(m)(受体库容量)、RE_(o)/RC(单个活性反应中心传递至光合系统Ⅰ末端电子受体使其还原的电子通量)、psi(E_(o))[开始照明时,由活性反应中心捕获的单个激子驱动除还原辅酶A(QA)外的电子传递的效率]、phi(E_(o))(开始照明时,还原辅酶A至除还原辅酶A外的电子传递链电子受体电子传递的量子效率)、delta(R_(o))(开始照明时,由活性反应中心捕获的单个激子驱动单个电子由QA经电子传递链至PSⅠ受体侧末端电子受体的效率)、phi(R_(o))(光系统Ⅰ受体侧末端电子受体还原的量子效率)、RE_(o)/CS_(m)(t=t F_(m),单个活性反应中心传递至PSI末端电子受体使其还原的能量通量)、PI abs(以吸收光能为基础的性能参数)呈现显著正相关,与ABS/RC(单位反应中心吸收的光能)、DI_(o)/RC(单个活性反应中心耗散的总能量)、TR_(o)/RC(单位反应中心捕获的用于还原辅酶A的能量)呈现极显著负相关。主成分最小数据组分析得出,PI_(total)、ET_(o)/RC(单位反应中心传递的能量)、ET_(o)/CS_(m)(达到荧光测量最大值时,单位叶面积用于电子传递的能量)、净光合速率(P_(n))和气孔导度(G_(s))可作为油莎豆高光效种质资源鉴选的重要指标。聚类分析结果表明,40份种质资源可划分为3类。其中,第Ⅰ类群有16份种质,主要表现为P_(n)、G_(s)显著高于其他2个类群。第Ⅱ类群有13份种质,主要表现为PI_(total)显著高于其他2个类群,第Ⅰ类群和第Ⅱ类群的ET_(o)/RC、ET_(o)/CS_(m)显著高于第Ⅲ类群。第Ⅲ类群有11份种质,各参数均低于其他2个类群。不同粒型种质间差异分析结果显示,圆粒型种质的ET_(o)/RC极显著高于长粒型种质,而长粒型种质综合得分显著高于圆粒型种质。本研究模型评价结果表明,XJ8、JL7、HE9综合表现较好,可作为高光效资源材料,为油莎豆种质资源的进一步创新和利用提供重要的参考。

6-BA缓解黄瓜弱光胁迫的浓度研究

在温室条件下,研究喷施不同浓度6-苄氨基嘌呤(6-BA)对弱光条件下不同类型黄瓜气体交换参数和叶绿素荧光参数的影响。结果表明,华南型杂交组合‘07QP56’在10μmol/L 6-BA处理条件下,欧洲迷你型杂交组合‘07QP51’在2,5μmol/L6-BA处理时,可以较为明显地缓解由弱光导致的饱和光合速率(Asat)、气孔导度(Gs)和蒸腾速率(Tr)降低的现象。同时,10μmol/L 6-BA处理对缓解弱光下‘07QP56’的PSⅡ潜在活性(Fv/Fo)、原初光能转化效率(Fv/Fm)的降低也有一定的效果。‘07QP51’较‘07QP56’耐弱光,并且对高浓度6-BA处理也更为敏感。

NaCl胁迫对草莓不同叶龄叶片光合及生理指标的影响

以红颊草莓为材料,研究了NaCl胁迫处理对不同叶龄叶片光合及生理指标的影响,结果表明:叶绿素初始荧光中潜在荧光Fv/Fo对盐胁迫敏感,功能叶片潜在荧光参数显著降低。在光适应叶绿素荧光参数中,PSⅡ实际光化学效率、光化学猝灭、光化学速率等在新叶和老叶上均表现为明显降低。盐胁迫显著降低了草莓植株功能叶片的净光合速率、气孔导度和蒸腾速率等,但可提高草莓功能叶片的MDA含量以及抗氧化酶SOD、POD的活性。

NaCl胁迫对苦豆子幼苗光合机构及生物量积累的影响

该研究通过测定盐生药用植物苦豆子幼苗气体交换、叶绿素荧光参数及生长指标,研究了中度(200mmol/L NaCl)和重度(400mmol/L NaCl)盐胁迫对其生长特性的影响,探讨盐生植物对盐化环境的生理响应机制。结果显示:(1)中度盐胁迫1d后,苦豆子幼苗光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)及胞间二氧化碳浓度(C_i)显著低于对照,随着胁迫时间延长,P_n下降显著,而气体交换参数降低不明显,C_i值甚至有上升趋势;重度盐胁迫处理1d后,苦豆子气体交换值出现了显著降低,随着胁迫时间延长,降低程度增大;中度盐胁迫导致苦豆子光合速率出现下降的原因是由气孔因素和非气孔因素共同作用的结果,而重度盐胁迫下,Pn的下降主要是非气孔因素引起的。(2)处理1d后,相对于对照组,中度和重度盐胁迫下的苦豆子幼苗最大光化学效率(F_v/F_m)、光化学猝灭系数(qP)、实际光化学效率(Φ_(PSⅡ))出现了不同程度的降低,而重度盐胁迫下降低更加显著;处理5d后,中度盐胁迫荧光参数变化不明显,但重度盐胁迫处理下降低显著。(3)随着胁迫程度的加重,幼苗含水量及生长指标(株高、根长、干重)降低幅度加大,以致严重抑制了植株生长。研究表明,盐生植物苦豆子对盐胁迫的耐受性也有一定限度,其在200mmol/L NaCl胁迫下植株光合作用受到轻微抑制,但能维持正常生长,而在400mmol/L NaCl胁迫下光合生理受到严重抑制,且随着胁迫时间的延长,受到伤害程度加重,甚至死亡。

外源钙对盐碱胁迫下万寿菊生长及光合特性的影响

【目的】探究外源CaCl_(2)对盐碱胁迫下万寿菊生长和光合特性的影响,为应用CaCl_(2)提高盐碱地上万寿菊栽培效率和产品品质提供理论支撑。【方法】以万寿菊幼苗为试材,设置浇灌清水(CK_(1))、根灌80 mmol/L混合盐碱溶液(CK_(2))和根灌盐碱后叶面喷施4种浓度CaCl_(2)溶液处理(5,10,15,20 mmol/L)进行盆栽试验,观测植株生长表型、叶片光合色素含量、光合气体交换参数和叶绿素荧光参数。【结果】随着盐碱胁迫时间延长,万寿菊植株的株高、茎粗、根系构型和根冠比呈逐渐上升趋势,叶片净光合速率(P_(n))、蒸腾系数(T_(r))、气孔导度(G_(s))、叶绿素总量(Chl_(t))和最大光化学效率(F_(v)/F_(m))等均呈下降趋势,而胞间CO_(2)浓度(C_(i))呈上升趋势,但这些指标在叶面喷施不同浓度CaCl_(2)后变化幅度均有所降低,并均以10 mmol/L CaCl_(2)处理效果最佳。在胁迫第20天时,10 mmol/L CaCl_(2)处理叶片Chl t、P_(n)、T_(r)、G_(s)、F_(v)/F_(m)分别比CK_(2)显著升高46.78%、45.53%、49.51%、49.57%和32.83%,其根冠比和C_(i)则分别显著降低22.60%和30.91%。【结论】叶面喷施10 mmol/L CaCl_(2)可显著减轻盐碱胁迫下万寿菊叶片叶绿素含量降幅,提高PSⅡ的电子传递速率,增强叶片的光合能力,有效改善植株生长。

青岛市3种常绿灌木滞尘量与叶微观特征及光合作用等的相关性分析

为探讨滞尘后3种灌木叶片叶绿素含量、叶绿素荧光参数以及气体交换参数的变化,分析叶面微结构以及叶绿素荧光参数、气体交换参数与植物滞尘量的相关性。以青岛市城阳区3种常见的常绿灌木为研究对象,通过3级滤膜过滤法测定各灌木单位叶面积滞留不同粒径颗粒物(TSP、PM>10、PM_(10)、PM_(2.5))的质量,通过扫描电镜观察比较3种常绿灌木的叶表面微形态特征。结果表明,1)3种灌木叶片单位叶面积滞尘能力为火棘>瓜子黄杨>小叶女贞。2)电镜扫描叶表面微结构可知,叶表面粗糙、下表皮气孔较多且分布密集,起伏大,存在不规则条纹组织及沟状组织的植物有利于颗粒物的附着,主成分分析发现3种灌木的单位叶面积TSP仅与植物的下表皮沟槽宽度呈现出正相关关系,与其他指标无显著相关性。3)滞尘后3种灌木叶片叶绿素含量、最大光化学效率(F_(v)/F_(m))和光化学猝灭系数(qP)显著(P<0.05)低于滞尘前处理,而非光化学猝灭系数(NPQ)则显著高于滞尘前处理;此外,3种灌木叶片净光合速率(P_(n))、蒸腾速率(T_(r))、气孔导度(G_(s))和胞间CO_(2)浓度(C_(i))差异显著,与滞尘前相比,滞尘后3种灌木的P_(n)、T_(r)、G_(s)分别下降27.1%、44.2%、7.1%,7.9%、38.3%、19.7%和38.0%、38.7%、11.6%,C_(i)分别增加8.2%、5.1%、4.9%,主成分分析可知,3种灌木的单位叶面积TSP与叶绿素含量、F_(v)/F_(m)以及P_(n)呈显著或极显著负相关,与C_(i)呈显著正相关。结论认为,叶表面粗糙度、气孔数量及大小、沟槽宽度等影响植物的滞尘能力,滞尘对植物叶片叶绿素以及叶绿素荧光参数产生一定程度的影响,降低植物叶片的光合作用,后期可考虑选择火棘作为滞尘能力强的灌木树种。

Impact of air drought on photosynthesis efficiency of the Siberian crabapple(Malus baccata L. Borkh.) in the forest-steppe zone of Transbaikalia, Russia

The adaption of photosynthesis, being a key metabolic process, plays an important role in plant resistance to air drought. In this study, the Siberian crabapple(Malus baccata L. Borkh.) in the forest-steppe zone of Transbaikalia region, Russia, was subjected to air drought stress and its photosynthesis characteristics were analyzed. The results show that air drought and sufficient soil moisture supply lead to the decrease in the total chlorophyll(Chl) content, while the ratio of Chls to carotenoids is constant in the Siberian crabapple tree. The function of photosystem II(PS-II) in the crabapple trees is characterized by a decrease in the fraction of absorbed light energy spent on the photochemical work and an increase in the proportion of non-photosynthetic thermal quenching. These changes indicate the photosynthetic down-regulation that acts as a universal photoprotective mechanism. During the midday hours, the combination of high air temperature and low air humidity leads to the decrease in the maximum photochemical quantum yield of photosystem II(Fv/Fm) and the efficiency of photosynthesis(PABS). The parameters of leaf gas exchange show the significant differences in these values between the control and experimental variants. During the morning hours, the Siberian crabapple, growing in the Irkutsk City,assimilates carbon dioxide more intensively. Due to the higher air humidity, the stomata are kept open and the necessary amount of carbon dioxide entries the sites of carboxylation. The low air humidity combined with wind in the experimental variants leads to the unreasonably high water loss in the crabapple leaves by more than 27% as compared to the control variant(Irkutsk City). However, water use efficiency in the morning hours increases during plant photosynthetic processes, i.e., 42% higher than that of control. This,apparently, is a reflection of the adaptation processes of the Siberian crabapple to the air drought and parching wind.

双酚A对合果芋叶片气体交换参数、叶绿素荧光参数和氧化损伤的影响

目前双酚A(bisphenol A,BPA)已经成为一种全球性的环境污染物。以合果芋(Syngonium podophyllumSchott,SPS)为研究对象,采用水培试验的方式,在0、10、30和50 mg·L^(-1)的BPA处理下,研究了BPA对合果芋叶片光合色素、气体交换参数、叶绿素荧光参数和氧化损伤的影响。研究结果显示,所有BPA处理的合果芋叶片叶绿素a、叶绿素b、总叶绿素和类胡萝卜素的含量均低于对照组(6.4%~32.5%),且随BPA胁迫浓度和时间的增加呈下降趋势。30 mg·L^(-1)和50 mg·L^(-1)的BPA处理明显降低了合果芋叶片净光合速率(Pn)、蒸腾速率(T_(r))、气孔导度(G_(s))、最大荧光产量(F_(m))和PSⅡ最大光能转化效率(F_(v)/F_(m))值,但增加了胞间CO_(2)浓度(C_(i))和初始荧光(F_(0))值。合果芋叶片过氧化氢(H_(2)O_(2))、丙二醛(MDA)含量和电解质渗透率(EC)在30 mg·L^(-1)和50 mg·L^(-1)的BPA处理下,随着胁迫时间的增加呈现不同程度的递增,而在10 mg·L^(-1)的BPA处理下,3 d内略有上升,而后趋于稳定。上述结果表明在30 mg·L^(-1)和50 mg·L^(-1)的BPA处理下,合果芋的植物生理代谢出现了一定的紊乱现象,而10 mg·L^(-1)的BPA对合果芋的正常生长影响较小。

Systemic regulation of photosynthetic function in maize plants at graining stage under a vertically heterogeneous light environment

To cope with a highly heterogeneous light environment,photosynthesis in plants can be regulated systemically.Currently,the majority of studies are carried out with various plants during the vegetative growth period.As the reproductive sink improves photosynthesis,we wondered how photosynthesis is systemically regulated at the reproductive stage under a vertically heterogeneous light environment in the field.Therefore,changes of light intensity within canopy,chlorophyll content,gas exchange,and chlorophyll a fluorescence transient were carefully investigated at the graining stage of maize under various planting densities.In this study,a high planting density of maize drastically reduced the light intensities in the lower canopy,and increased the difference in vertical light distribution within the canopy.With the increase of vertical heterogeneity,chlorophyll content,light-saturated photosynthetic rate and the quantum yield of electron transport in the ear leaf(EL) and the fourth leaf below the ear(FLBE) were decreased gradually,and the ranges of declines in these parameters were larger at FLBE than those at EL.Leaves in the lower canopy were shaded artificially to further test these results.Partial shading(PS) resulted in a vertically heterogeneous light environment and enhanced the differences in photosynthetic characteristics between EL and FLBE.Removing the tassel and top leaves(RTL) not only improved the vertical light distribution within the canopy,but also reduced the differences in photosynthetic characteristics between the two leaves.Taken together,these results demonstrated that maize plants could enhance the vertical heterogeneity of their photosynthetic function to adapt to their light environment;slight changes of the photosynthetic function in EL at the graining stage under a vertically heterogeneous light environment indicated that the systemic regulation of photosynthesis is weak at the graining stage.

Physiological Responses of <i>Tamarix ramosissima</i>to Extreme NaCl Concentrations

Hydrologic alterations of river systems in western North America over the past century have increased soil salinity, contributing to the establishment and spread of an introduced halophytic species, Tamarix ramosissima (Ledeb.). The physiological responses of Tamarix ramosissima to salinity stress are incompletely known. To assess the salinity tolerance of this species, we measured several whole plant and leaf-level physiological responses of Tamarix ramosissima cuttings grown in a controlled environment over three NaCl concentrations (0, 15 and 40 g l-1). Tamarix ramosissima photosynthesis (A2000), stomatal conductance to water (gs), water potential (Ψw), and the maximum quantum yield of photosystem II (Fv/Fm) decreased at 15 and 40 g l-1 NaCl compared to control treatments. However, after approximately 35 days, Tamarix ramosissima had increased photosynthetic rates, maximum quantum yield of photosystem II, and stomatal conductance to water. These data suggests that physiological functioning of Tamarix ramosissima acclimated to extremely high NaCl concentrations over a relatively short period of time. Additionally, we present preliminary evidence that suggests proline synthesis may be the mechanism by which this species adjusts osmotically to increasing salinity.