Field crop responses to ultraviolet-B radiation: a review

This paper provides an overview of existing literature on the ultraviolet-B (UV-B) radiation effects on field crops. Earlier reviews on field crop responses to UV-B considered few physiological processes or crops. For this review, we easily located about 129 studies on 35 crop species published since 1975. Here, we report the effects of UV-B radiation on visual symptoms, leaf ultrastructure and anatomy, photosynthetic pigments, UV-B absorbing compounds, photosynthesis, growth and development, yield, genotypic differences, and finally, interactions of UV-B with abiotic and biotic factors of crop plants. Experiments conducted in glasshouses, in closed and open top chambers, and under field conditions, with varying source (solar or artificial) and intensity of photosynthetically active radiation (PAR, 50–1800 μmol m⁻² s⁻¹) and UV-B (0–50 kJ m⁻² per day) are included. It is easy to conduct experiments that purport to evaluate the effects of projected UV-B intensities on crop species by providing supplemental irradiance with lamps or by reducing UV-B with filters; however, it is very difficult to simulate UV-B irradiance spectral changes that are likely to occur in nature. Collated results for each process are presented as percent change from control along with the experimental conditions in tabular format. Many of the studies showed dramatic effects of UV-B radiation, but under conditions with supplemental UV-B irradiance that was higher than would ever occur outside experimental conditions or in which the longer wavelengths in the PAR and UV-A, which moderate UV-B effects, were greatly reduced. Only 25 of the studies reviewed used experimental conditions and supplemental UV-B irradiance that approached realism. However, unrealistic the experimental conditions might be, an increase in understanding of basic plant physiology was gained from most of the studies.Visual symptoms consisting of chlorotic or necrotic patches on leaves exposed to UV-B were not unique. Both vegetative and reproductive morphology were altered by UV-B radiation. Leaf anatomy was altered due to changes in thickness of epidermal, palisade, and mesophyll layers. Enhanced UV-B generally decreased chlorophyll content (10–70%), whereas it increased UV-B absorbing compounds (10–300%) in many crops. Decrease in photosynthesis (3–90%), particularly at higher UV-B doses, was due to both direct (effect on photosystem) and indirect (decrease in pigments and leaf area) effects. The decreases in chlorophyll pigments and photosynthesis resulted in lower biomass and yield of most crop plants. Genotypes of crop species exhibited variability in leaf wax layer thickness, loss of chlorophyll, and increase in phenolics as mechanisms of tolerance to enhanced UV-B radiation resulting in changes in biomass/yield. Results from the few studies on interaction of UV-B with other abiotic and biotic factors did not lead to useful conclusions. Studies are needed to quantify the effects of UV-B radiation on crops in order to develop dose response functions that can facilitate development of dynamic simulation models for use in UV-B and other environmental impact assessments.     

Responses in Some Growth and Mineral Elements of Mono Maple Seedlings to Enhanced Ultraviolet-B and to Nitrogen Supply

The effects of enhanced ultraviolet-B (UV-B) and nitrogen supply on the growth and mineral elements of mono maple (Acer mono Maxim) seedlings were studied in open semi-field conditions. Mono maple is a common species in reforestation processes in the southeast of the Qinhai-Tibetan Plateau of China. The experimental design included two levels of UV-B treatments (ambient UV-B, 11.02 KJ/m²/day; enhanced UV-B, 14.33 KJ/m²/day) and two nitrogen levels (0; 20 g N/m²/a). No visible symptoms of nutrient deficiency were observed in seedlings grown under enhanced UV-B radiation during the experiment. However, there was visible damage of enhanced UV-B radiation on leaves. Enhanced UV-B significantly reduced plant height and biomass of plants, and changed biomass allocation between organs under supplemental nitrogen supply, which lead to a decrease in root/shoot ratio. On the other hand, nitrogen supply significantly increased plant height and biomass under ambient UV-B, whereas it reduced root mass and root weight ratio, and increased stem mass and stem weight ratio under enhanced UV-B. In addition, enhanced UV-B radiation and nitrogen supply significantly affected the concentration and allocation of most nutrients in various organs, and nitrogen supply could changed the effects of enhanced UV-B on mineral element in plant parts to some extent, which may have significant impacts on nutrient cycling and may lead to the disorder of nutrient balanced and influence the growth of plants.     

Yield and yield formation of field winter wheat in response to supplemental solar ultraviolet-B radiation

The stratospheric ozone decrease has heightened concern over the ecological implications of increasing solar UV-B radiation on agricultural production and natural plant ecosystems. UV-B is absorbed, and can damage many important plant species through a variety of interacting mechanisms. The effects of enhanced UV-B exposure on yield and yield formation of winter wheat associated with photosynthetic activity and total biomass development were investigated in this study. The overall experimental design included three UV-B treatments (two supplemental UV-B treatments and an ambient level) with three replicates of each treatment. Results suggested that the supplemental UV-B can cause the decrease of yield of winter wheat up to 24% with 11.4% increased UV-B. Supplemental UVB decreased dry matter accumulation most during the jointing–booting stage when the leaf area index (LAI) was the greatest. In addition, the supplemental U-VB appeared to effect the distribution of dry matter but did not effect the net assimilation ratio of the wheat.     

增强紫外线-B辐射冬小麦产量和光合特性的影响

为了研究紫外线-B（ultraviolet-B UV-B, 280-320nm）辐射增强20%对保护性耕作冬小麦产量及光合特性的影响,在中国南京开展了2 a的田间试验研究。试验采用常规耕作（耕深25 cm）、少耕（耕深10 cm）和免耕（土壤不耕作）3种耕作处理种植冬小麦,采用人工增加紫外辐射的方法模拟UV-B辐射增强。试验测定了冬小麦旗叶的光合速率、光合-光响应曲线、叶绿素质量分数、超氧化物歧化酶（superoxide dismutase, SOD）活性、丙二醛（malonaldehyde, MDA）质量分数和可溶性蛋白质量分数等指标。结果表明：在UV-B辐射增强20%条件下,与常规耕作相比,少耕和免耕2种保护性耕作处理可显著提高冬小麦的产量,分别比常规耕处理作高1632.12和952.15 kg/hm2。从叶片光合生理特性来看,在UV-B辐射增强20%条件下,从冬小麦籽粒灌浆中期开始,少耕和免耕处理旗叶的光合速率、表观量子效率（apparent quantum yield, AQY）、最大净光合速率（Pmax）、叶绿素质量分数、SOD活性、可溶性蛋白质的质量分数显著高于常规耕作处理,MDA质量分数显著低于常规耕作处理,2种处理冬小麦的叶片衰老显著低于常规耕作处理。在UV-B辐射增强20%条件下,少耕和免耕2种保护性耕作处理冬小麦旗叶在籽粒灌浆中期及以后保持高的光合能力和低的衰老程度,是其产量高于常规耕作处理的原因。该文可为制定UV-B辐射增强条件下的冬小麦栽培措施提供参考。     

大田条件下模拟UV-B辐射滤减对水稻生长及内源激素含量的影响

对大田栽培条件下人工模拟的UV-B辐射滤减环境对晚稻品种“协优432”的叶绿素含量、株高、内源激素吲哚乙酸(IAA)、脱落酸(ABA)、赤霉素(GA3)、玉米素(Zeatin)含量的影响研究结果表明,在正常日光处理组与UV-A滤光组之间叶绿素a含量变化显著;正常日光处理组与UV-A滤光组、UV-A UV-B滤光组之间株高无明显变化。UV-A UV-B滤光组IAA、GA3、Zeatin含量分别比正常日光处理组降低了40.42%、48.60%、36.21%;分别比UV-A滤光处理组降低了36.52%、70.94%、54.54%。单因素方差分析及多重比较结果显示,UV-A UV-B滤光组与正常日光处理组之间IAA、GA3含量差异显著;UV-A UV-B滤光组与UV-A滤光处理组之间GA3、Zeatin含量差异显著。UV-A UV-B滤光组ABA含量比正常日光处理组降低了29.74%,比UV-A滤光处理组降低了5.19%,经单因素方差分析后发现差异不显著。     

Impact of enhanced ultraviolet-B irradiance on cotton growth, development, yield, and qualities under field conditions

The stratospheric ozone depletion and enhanced solar ultraviolet-B (UV-B) irradiance may have adverse impacts on the productivity of agricultural crops. The effect of UV-B enhancements on agricultural crops includes reduction in yield, alteration in species competition, decrease in photosynthetic activity, susceptibility to disease, and changes in structure and pigmentation. Many studies have examined the influence of supplemental UV-B irradiance on different crops, but the effect of UV-B irradiance on cotton (Gossypium hirsutum L.) crops has received little attention. Cotton is one of the most versatile of all the crops. It is a major fiber crop of the world and a major source of trade and economy in many countries. In this study, we provide quantitative examination of the effects of elevated UV-B irradiance on cotton plant (Sukang 103). The tested cotton crop was grown under natural and four regimes of supplemental UV-B irradiance in the field. With UV-B irradiance increased 9.5% throughout the growing season, the negative impacts on cotton growth included reductions in height of 14%, in leaf area of 29%, and in total biomass of 34%. Fiber quality was reduced and economic yield dropped 72%; an economic coefficient was reduced 58%. A brief discussion is included on how the impacts on cotton contrast with impacts that have been observed in other studies on other plants, including trees.     

The combined effects of enhanced UV-B radiation and selenium on growth, chlorophyll fluorescence and ultrastructure in strawberry (Fragaria × ananassa) and barley (Hordeum vulgare) treated in the field

The possible ameliorative effects of selenium (Se) addition to soil on the detrimental effects of enhanced UV-B radiation were tested on strawberry and barley during 4 months of field experiment in Kuopio, Central Finland. Control plants were exposed to ambient levels of UV radiation, using arrays of unenergized lamps. A control for UV-A radiation was also included in the experiment. Added Se, applied as H₂SeO₄, at the level of 0.1 mg kg⁻¹ soil (low dosage) and 1 mg kg⁻¹ soil (high dosage) increased Se concentrations in plants more than 10 and 100 times, respectively. After 4 months of exposure, strawberry and barley plants were harvested for biomass analysis. Chlorophyll fluorescence was measured using the Hansatech FMS2 fluorescence monitoring system. Leaf anatomy and ultrastructure were observed by light and transmission electron microscope. Several effects of UV and Se as well as their interaction were found, mostly for strawberry, but not for barley, indicating species-specific responses. Our results provided evidence that the high Se concentration in soil had no ameliorative effect but increased the sensitivity of strawberry to enhanced UV-B radiation in the field. Under ambient radiation, Se did not alter leaf growth of strawberry, whereas under UV-B radiation, the high Se addition significantly decreased leaf growth. Strawberry runner biomass was affected by the interaction of Se and UV. Under ambient radiation Se did not change dry weight of runners, but in combination with UV-A or UV-B radiation the high Se dosage decreased dry weight of runners by about 30%. Although the high Se concentration positively influenced on quantum efficiency of photosystem II (PSII) in strawberry leaves, it reduced runner biomass, leaf number and ratio of starch to chloroplast area. This suggests that the harmful effects of the high Se dosage on photosynthetic processes occurred as a result of changes in activity or/and biosynthesis of enzymes, rather than alteration of PSII. At the low concentration, Se effects were slight and variable.Although barley leaves accumulated higher Se concentrations than strawberry, there were no apparent changes in their growth, biomass or chlorophyll fluorescence due to Se effect either alone or in combination with UV-B. However, at the ultrastructural level, an enlargement in the peroxisome area was found due to combination of UV radiation with Se, suggesting the activation of antioxidative enzymes, possibly catalase. Decrease in mitochondrial density in barley cells in response to Se might be attributed to alteration of mitochondrial division. Increase in the proportion of cells with cytoplasmic lipid bodies due to combined effect of UV-B and Se indicated the alteration of lipid metabolism and the acceleration of cell senescence in barley. Main UV-B effects were found, mostly at the tissue and ultrastructural level in strawberry, but not in barley, indicating species-specific susceptibility to enhanced UV-B radiation. UV-B-treated strawberry plants developed marginally thinner leaves with reduced ratio of starch to chloroplast area in their cells, suggesting negative influence of UV-B on photosynthetic processes.     

UV-B增强下施硅对大麦抽穗期光合和蒸腾生理日变化的影响

通过大田模拟试验,研究UV-B增强下施硅对大麦抽穗期叶片净光合速率（Pn）、蒸腾速率（Tr）、气孔导度（Gs）、胞间二氧化碳浓度（Ci）和水分利用效率（WUE）日变化的影响。UV-B辐射设2个水平即自然光（对照,A,1.5kJ·m-2）和UV-B增强（E,增强20%,1.8kJ·m-2）,施硅量设2个水平即Si0（不施硅）和Si1（150kg·hm-2SiO2）。结果表明,不施硅情况下（Si0）,UV-B增强处理的Pn、Tr、Gs和WUE的日平均值比自然光（A）处理分别下降23.13%、7.66%、1.07%和16.38%,而施硅情况下（Si1）则分别下降10.52%、5.71%、3.77%和12.15%,说明UV-B增强可降低大麦叶片的净光合速率、蒸腾速率和水分利用效率,而施硅可缓解UV-B增强对大麦净光合速率的抑制作用,但并不能缓解UV-B增强对大麦蒸腾作用以及气孔导度的抑制。研究结果对进一步研究UV-B增强下施硅对大麦产量和品质的影响具有积极意义。     

Elevated UV-B radiation modifies the extractability of carbohydrates from leaf litter of Quercus robur

We examined the influence of elevated UV-B radiation on the extractability of carbohydrates from leaf litter of Quercus robur. Saplings were exposed to a 30% elevation above the ambient level of erythemally weighted UV-B (280-315 nm) radiation for eight months at an outdoor facility. UV-B radiation was applied under arrays of fluorescent lamps filtered with cellulose diacetate, which transmitted both UV-B and UV-A (315-400 nm) radiation. Saplings were also exposed to elevated UV-A radiation under arrays of polyester-filtered lamps and to ambient radiation under arrays of non-energised lamps. Abscised leaves were collected, ground and sequentially treated with seven solvents in order to fractionate extractable carbohydrates based on the way in which they are held in the cell wall. Elevated UV-B radiation reduced the extractability of carbohydrates from cell walls of Q. robur. Sodium phosphate buffer at pH 7 extracted 10% less total carbohydrate from leaf material exposed during growth to elevated UV-B radiation under cellulose diacetate-filtered lamps than from leaf material grown under polyester-filtered and non-energised lamps. The cumulative amount of carbohydrate released by sequential extraction with phosphate buffer, CDTA, urea and sodium carbonate was between 5.1% and 7.8% lower from leaf material grown under cellulose diacetate-filtered lamps relative to that from leaves grown under non-energised lamps. Abscised leaves were also digested with Driselase, an enzyme mixture extracted from a basidiomycete fungus. No effects of elevated UV radiation were recorded on the amount of carbohydrate released by Driselase digestion. Regression analyses, using data from a previous field decomposition study, suggested that reduced availability of carbohydrates enhanced the colonisation of Q. robur litter by basidiomycete fungi, which then accelerated the decomposition rate of the litter in soil. We recommend that future studies into the effects of UV-B radiation on plant litter decomposition measure not only the concentrations of chemical constituents of litter, but also determine the availability of litter carbon sources to soil microbes, using methods similar to those used here.     

UV-B增强下施硅对水稻冠层反射光谱特征的影响

通过田间试验,在UV-B增强和施硅条件下,利用ASD便携式手持光谱仪在水稻分蘖期、拔节期、抽穗期和灌浆期选择典型晴天观测冠层光谱曲线,通过计算一阶导数曲线分析光谱的红边参数特征。UV-B辐射设2个水平,即对照(自然光,ambient UV-B,A)和UV-B增强(比自然光增强20%,elevated UV-B,E);施硅设2个水平,即不施硅和施硅(硅酸钠,200kg SiO_2·hm~(-2))。结果表明:UV-B增强下水稻叶面积指数(LAI)和叶绿素含量(SPAD值)降低,而施硅可提高叶面积指数(LAI)和SPAD值,缓解UV-B增强对水稻生长的抑制作用。各处理间水稻冠层光谱的差异主要体现在近红外波段,UV-B增强使水稻近红外波段反射率降低,施硅使近红外波段反射率上升。UV-B增强使水稻光谱红边位置蓝移,施硅使红边位置红移。随着生育期推移,水稻光谱红边位置、红边幅值和红边面积均呈现先增后减的趋势,且在拔节期达最大。     

SILICON MITIGATES ULTRAVIOLET-B RADIATION STRESS ON SOYBEAN BY ENHANCING CHLOROPHYLL AND PHOTOSYNTHESIS AND REDUCING TRANSPIRATION

The aim of this study was to investigate the potential of silicon (Si) for alleviating Ultraviolet-B (UV-B) radiation stress based on changes in biomass, physiological attributes and photosynthetic characteristics of two soybean (Glycine max L.) cultivars, Kenjiandou 43 (‘K 43’) and Zhonghuang 35 (‘ZH 35’). The cultivars were raised with and without Si in the greenhouse, and then subjected to ambient, ambient + 2.7 kJ m^?2d^?1and ambient + 5.4 kJ m^?2d^?1of UV-B radiation. Depending on cultivar, plants suffered severe growth limitations under UV-B radiation, but the application of Si alleviated the adverse effects on growth and development by increasing the stem length, net photosynthetic rate (P_N) and leaf chlorophyll content. Concurrently, it decreased the stomatal conductance (Sc) and intercellular carbon dioxide (CO₂) concentration (Ci). In response to the UV-B radiation stress, the antioxidant enzyme activities of superoxide dismutase (SOD) increased by 41.2–72.7%, peroxidases (POD) by 49.5–85.7%, malodialdehyde (MDA) by 6.7–20.4% and soluble protein by 4.2–7.6%. The overall results indicated that media treatment with Si might improve soybean growth under elevated UV-B radiation through positive changes in biomass and some physiological attributes that were dependent on cultivar.     

UV-B增强下施钾对大麦抽穗期生理特性日变化的影响

通过大田试验,研究在UV-B增强条件下,不同施钾量对大麦抽穗期叶片净光合速率、气孔导度、蒸腾速率、胞间CO2浓度和水分利用率等生理指标日变化的影响。UV-B辐射设2水平,即对照(CK,自然光,辐射强度1.5 KJ/(m2·h))和增强120%(1.8 KJ/(m2·h));施钾量设2水平,即低钾(K1,K2O 73 kg/hm2)和高钾(K2,K2O 150 kg/hm2)。结果表明,UV-B增强降低大麦的叶绿素含量、净光合速率、气孔导度、蒸腾速率和水分利用率。增施钾肥可提高叶片中叶绿素的含量、净光合速率、气孔导度和蒸腾效率,但对大麦胞间CO2浓度和水分利用效率的影响不明显。增施钾肥可减缓UV-B增强对大麦净光合速率的抑制作用,但不能减缓UV-B增强对大麦气孔导度和蒸腾速率的抑制作用。     

Direct and indirect effects of ultraviolet-B radiation on soil biota, decomposition and nutrient fluxes in dune grassland soil systems

 Enhanced UV radiation did not show any effect on the decomposition of a mixed litter of the dune grassland plant species Calamagrostis epigeios and Carex arenaria. Also, leaching of nutrients from lysimeters filled with dune grassland soils was not affected by enhanced UV radiation. Negative UV effects on the fungal biomass in the first part of the experiment were later reversed into positive ones. Clear effects of both UV-A and UV-B were found on Collembola, both on total number of individuals and on the number of species. The decreased number of species under UV radiation could have been due to a decrease in UV-sensitive species. The role of pigmentation is discussed. Received: 6 July 1999     

外源水杨酸对UV-B增强下花生叶片光合特性的影响

通过大田模拟试验,设置自然光（CK）和UV-B辐射增强（E,增加量相当于当地4-5月UV-B辐射量的20%）两个大区,在每个大区内又分2个小区,从花针期（7月25日）开始,分别用蒸馏水（S0处理）和水杨酸水溶液（SA处理）连续3d在固定时段喷施花生植株的所有叶片后,用Li-6400型便携式光合作用测定仪观测和计算指定叶片的净光合速率（Pn）、蒸腾速率（Tr）、气孔导度（Gs）、胞间CO2浓度（Ci）和水分利用效率（WUE）的日变化过程,并进行对比分析。结果表明：不施水杨酸条件下（S0）,UV-B增强处理的花生叶片Pn、Tr、Gs和WUE的日均值比自然光（CK）处理分别下降35.7%、25.0%、25.0%、10.0%;而喷施水杨酸条件下（SA）则分别下降30.4%、17.9%、33.3%、19.4%,说明UV-B增强可降低花生叶片的净光合速率、蒸腾速率、气孔导度和水分利用效率,而喷施水杨酸可缓解UV-B增强对花生净光合速率的抑制作用,但并不能缓解UV-B增强对花生蒸腾作用、气孔导度及水分利用效率的抑制。     

Nutrient Acquisition by Soybean Treated with and without Silicon under Ultraviolet-B Radiation

The objective of this study was to determine if treatment with silicon (Si) may improve nutrient uptake by soybean under ultraviolet-B (UV-B) radiation stress. Soybean (Glycine max L.) cultivars, ‘Kennong 18’ (K 18) and ‘Zhonghuang 13’ (ZH 13), were grown in hydroponic cultures under ambient and supplemental levels of ultraviolet-B (UV-B, 280–315 nm) with and without Si. Supplemental UV-B radiation simulating 30% stratospheric ozone depletion significantly decreased plant biomass by 74.9 to 135.6%, increased leaf nitrogen (N) and phosphorus (P) by 9% and 16%, respectively, decreased leaf magnesium (Mg) contents by 9%, and calcium (Ca) by 24%. UV-B radiation caused a substantial increase in the allocation of P, potassium (K) and Ca to roots compared with stem and leaves, presumably to ensure sustained nutrient uptake under the stress. Silicon application improved the uptake of P and Mg by 11%, which favored the partitioning of dry mass to shoots under UV-B radiation and the allocation of tissue P and Ca to roots. The overall changes due to Si supported a reasonable increase in dry mass of the ‘K 18’ cultivar.     

铈对UV-B胁迫下大豆幼苗光合原初反应的影响

用水培法研究了Ce（Ⅲ）对紫外辐射（UV-B,280～320nm）胁迫下大豆幼苗光合原初反应的影响。结果表明,20mg·L-1CeCl3能有效减缓紫外辐射（T1/3.34kJ·m-2和T2/11.76kJ·m-2）胁迫所导致的叶绿素与类胡萝卜素含量减少、光能转换效率（Fv/Fm）及传递能力（Fv/F0）降低,且对低剂量胁迫的调控效果优于高剂量,即以上指标Ce＋T1〉T1,Ce＋T2〉T2,Ce＋T1〉Ce＋T2。从光合原初反应的能量分配看,Ce（Ⅲ）能促使大豆叶片吸收光能的总量增加,加快内囊体膜上光电的转换和电子的传递,降低UV-B辐射伤害而导致的过剩激发能积累,从而消除过剩激发能诱发的膜脂过氧化对光合器官的潜在威胁。     

不同光质补光对日光温室黄瓜产量与品质的影响

本试验采用不同的光质灯(蓝光、红光、UV-A、UV-B)对温室内黄瓜进行定时补光,研究不同补充光质对黄瓜果实Vc、蛋白质、还原糖含量及产量的影响。结果表明UV-B、红光条件下黄瓜Vc含量较UV-A与蓝光高;各处理蛋白质含量顺序为蓝光>UV-A>UV-B>红光;蓝光照射下还原糖含量较红光、UV-A与UV-B高;日光温室内补充UV-A可明显地增加黄瓜的产量。     

全生育期UV-B辐射增强对棉花生长及光合作用的影响

植物光合系统是UV-B辐射最初和最重要的作用靶标。本文在大田条件下进行紫外灯照射处理,研究全生育期UV-B辐射增强(高于环境20%和40%)对棉花形态、干物质积累、光合色素和产量的影响,并通过分析棉花主茎功能叶片的气体交换参数和叶绿素荧光参数,探讨UV-B辐射增强影响棉花光合作用的机制。结果表明,UV-B辐射增强抑制了棉花生长和干物质积累,籽棉产量显著降低,且UV-B辐射越强,抑制作用越明显。随UV-B辐射的增强,棉花主茎功能叶的净光合速率(P_n)在各生育期均显著降低,叶绿素含量呈先升高后降低趋势,气孔导度(Gs)和蒸腾速率(Tr)未发生变化,胞间CO_2浓度(Ci)反而升高,说明P_n下降主要由非气孔限制因素造成。对叶绿素荧光参数的分析表明,PSⅡ的最大光化学量子产率(F_v/F_m)、实际光化学量子效率(ΦPSII)、线性电子传递速率(ETR)和光化学淬灭系数(qP)随着UV-B辐射的增强而降低,非光化学猝灭系数(NPQ)则显著升高,且各叶绿素荧光参数与Pn变化均显著相关;慢速弛豫NPQ(NPQS)及其在NPQ中的比例均随UV-B辐射的增强而显著提高,表明PSⅡ反应中心受损,光化学效率降低。以上结果证明,全生育期UV-B辐射增强降低了棉花的光合叶面积、叶绿素含量和净光合速率,引起棉花生长与物质积累受抑,产量降低。UV-B辐射增强引起的光合速率下降与PSⅡ反应中心遭到破坏密切相关。     

初花期喷镧对UV-B辐射增强下紫花苜蓿光合及荧光特性的影响

在温室大棚内采用样方法条播和叶面喷施技术,以紫花苜蓿(Medicago sativa)为试验材料,UV-B辐射增强设5%(T1)和10%(T2)2个梯度,镧(Lanthanum)喷施设30、60和90mg·L-1 3个浓度,以植株上方悬挂灯架但不安装紫外灯管且不喷施镧的处理为对照(CK),研究UV-B辐射增强下喷施镧对紫花苜蓿光合及荧光特性的影响。结果表明:(1)在UV-B辐射增强条件下,紫花苜蓿叶片叶绿素a(Chla)、叶绿素b(Chlb)、净光合速率(A)、蒸腾速率(E)、气孔导度(gs)、胞间CO2浓度(Ci)、PSⅡ最大光化学量子产量(Fv/Fm)、光化学淬灭(q P)和非光化学淬灭(NPQ)均低于对照,表观光合电子传递效率(ETR)则高于对照(CK),说明UV-B辐射增强会降低紫花苜蓿叶片的光合特性。(2)喷施镧后,紫花苜蓿初花期、盛花期和成熟期叶片以上各指标均相应高于T_1和T_2处理,其中以在UV-B辐射增强5%条件下喷施30mg·L-1和UV-B辐射增强10%条件下喷施60mg·L~(-1)镧效果显著(P0.05),说明一定浓度的镧可以缓解UV-B辐射增强对紫花苜蓿光合特性造成的伤害,叶片光合作用得以增强;随着生育期的推进,紫花苜蓿叶片可溶性糖和可溶性蛋白含量持续上升,说明UV-B辐射和镧的喷施对紫花苜蓿叶片糖和蛋白的合成有一定促进作用。     

UV-B辐射增强对葡萄光合作用日变化的影响(简报)

大气臭氧层的不断破坏引起了地球表面紫外线-B(UV-B）辐射强度不断增加,这对植物的生长发育产生了重要影响。试验以酿酒葡萄（V.vinifera. L）“赤霞珠”（Cabernet Sauvignon）为材料,在自然光照条件下,通过增加不同强度的UV-B辐射,研究UV-B辐射增强对葡萄叶片光合作用日变化的影响,为进一步研究UV-B辐射增强对植物的影响提供依据。结果表明,UV-B辐射增强后葡萄叶片净光合速率（Pn）、气孔导度（Gs）、胞间CO2浓度（Ci）、蒸腾速率（Tr）均呈双峰型,且日变化平均值表现为低辐射（T₁,10.8 μW/cm²）处理组＞对照组（CK）＞高辐射（T₂,25.6 μW/cm²）处理组,而水分利用效率则表现为对照组（CK）＞低辐射（T₁,10.8 μW/cm2）处理组＞高辐射（T₂,25.6 μW/cm2）处理的变化趋势。同时,UV-B辐射增强对葡萄叶片中光合色素含量没有显著的影响。这说明UV-B辐射增强对葡萄光合作用的影响与UV-B辐射强度和照射时间有关,适当增加一定剂量的UV-B辐射对葡萄光合作用不会造成危害。