CO2浓度倍增和UV-B辐射增强对冬季大棚番茄生长、果实品质和产量的影响

在CO₂浓度倍增(700μmol·mol^-1)条件下,对补充5个不同低剂量的UV-B辐射对大棚番茄幼苗的株高、茎粗、干重、鲜重,果实的紫外吸收物、可溶性糖、有机酸、Vc、番茄红素等含量,以及果实产量的影响进行了研究。结果表明,CO₂倍增能够明显促进番茄幼苗的生长,提高了番茄果实的紫外吸收物、可溶性糖、有机酸、Vc、番茄红素等含量以及果实的产量。在CO₂倍增条件下,补充低剂量UV-B辐射可以进一步促进番茄幼苗的生长,提高番茄果实的紫外吸收物、可溶性糖、有机酸、Vc、番茄红素等含量,说明在CO₂倍增的条件下低剂量UV-B辐射对番茄的生长有促进效应,但对果实的产量影响不大。当UV-B的辐射剂量为1.163kJ·m^-2时,这种促进效应最明显,超过这一剂量时,UV-B辐射对番茄的促进效应开始减弱。     

Combined effects of enhanced ultraviolet-B radiation and doubled CO2 concentration on growth, fruit quality and yield of tomato in winter plastic greenhouse

Five different doses of ultraviolet-B (UV-B) radiation were supplied to tomato (Lycopersicon esculeutum. Mill) with the doubled CO₂ concentration (700 μmol · mol⁻¹) in the winter plastic greenhouse. The influences on the seedling growth, fruit quality and yield of tomato were investigated. Results showed that the seedling growth, and the contents of UV absorbing compounds, soluble sugar, organic acid, vitamin C and lycopene of tomato fruits, and yield of tomato increased under doubled CO₂ concentration. Under the doubled CO₂ concentration the effects of lost doses of UV-B radiation could further promote the effects of doubled CO₂ concentration. However, there is no significant increase in yield of tomato. The best dose of UV-B radiation is about 1.163 kJ·m⁻². When the dose of UV-B radiation is more than it, the effects of UV-B will be reduced. __________ Translated from Journal of Wuhan Botanical Research, 2006, 24(1): 49–53 [译自: 武汉植物学研究]     

UV-B辐射增强和CO2浓度倍增的复合作用对番茄生长和果实品质的影响

以番茄（Lycopersicon esculeutum）为研究对象,在人工模拟8.40 kJ·m^-2的UV-B辐射和700 μmol·mol^-1的CO₂浓度复合处理下,研究了番茄的生长和果实品质变化.结果表明,UV-B辐射使番茄的株高、鲜重、干重、总叶绿素、叶绿素a、叶绿素b、光合速率、水分利用效率、可溶性蛋白、维生素c及番茄红素等降低,导致果实品质恶化;而CO₂浓度倍增作用相反.在UV-B辐射增强和CO₂浓度倍增复合作用下,番茄的上述指标与对照相比差异不明显.分析认为,CO₂倍增与UV-B辐射增强复合处理下,CO₂的正效应作用可以减轻甚至抵消UV-B辐射的负效应.     

Nickel and Ultraviolet-B Stresses Induce Differential Growth and Photosynthetic Responses in Pisum sativum L. Seedlings

Enhanced level of UV-B radiation and heavy metals in irrigated soils due to anthropogenic activities are deteriorating the environmental conditions necessary for growth and development of plants. The present study was undertaken to study the individual and interactive effects of heavy metal nickel (NiCl(2)·6H(2)O; 0.01, 0.1, 1.0?mM) and UV-B exposure (0.4 W m(-2); 45?min corresponds to 1.08 KJ m(-2)) on growth performance and photosynthetic activity of pea (Pisum sativum L.) seedlings. Ni treatment at high doses (0.1 and 1.0?mM Ni) and UV-B alone reduced chlorophyll content and photosynthetic activity (oxygen yield, carbon fixation, photorespiration, and PSI, PSII, and whole chain electron transport activities), and declining trends continued with combined doses. In contrast to this, Ni at 0.01?mM appeared to be stimulatory for photosynthetic pigments and photosynthetic activity, thereby enhanced biomass was observed at this concentration. However, combined dose (UV-B + 0.01?mM Ni) caused inhibitory effects. Carotenoids showed different responses to each stress. Nickel at high doses strongly inhibited PSII activity and the inhibition was further intensified when chloroplasts were simultaneously exposed to UV-B radiation. PSI activity appeared to be more resistant to each stress. High doses of Ni (0.1and 1.0?mM) and UV-B alone interrupted electron flow at the oxygen evolving complex. Similar damaging effects were caused by 0.01 and 0.1?mM Ni together with UV-B, but the damage extended to PSII reaction center in case of 1.0?mM Ni in combination with UV-B. In conclusion, the results demonstrate that low dose of Ni stimulated the growth performance of pea seedlings in contrast to its inhibitory role at high doses. However, UV-B alone and together with low as well as high doses of Ni proved to be toxic for P. sativum L.     

Influence of ultraviolet-B radiation on photosynthetic and biochemical characteristics of a mangrove Rhizophora apiculata

Changes in photosynthesis and biochemical constituents were studied in R. apiculata seedlings grown under solar and solar enhanced UV-B radiation, equivalent to 10, 20, 30, and 40 % stratospheric ozone depletion. The seedlings grown under 10 % UV-B radiation showed an increase of 45 % net photosynthetic rate (PN) and 47 % stomatal conductance, while seedlings grown under 40 % UV-B radiation exhibited a decrease of 59 % PN with simultaneous elevation of 73 % intercellular CO2 concentration. Effects of UV-B on contents of lipids, saccharides, amino acids, and proteins were significant only at high doses of UV-B radiation. The concentration of anthocyanin was reduced with increasing doses of UV-B. The reverse was true with phenols and flavonoids.     

Influence of ultraviolet-B radiation on photosynthetic and biochemical characteristics of a mangrove Rhizophora apiculata

Changes in photosynthesis and biochemical constituents were studied in R. apiculata seedlings grown under solar and solar enhanced UV-B radiation, equivalent to 10, 20, 30, and 40 % stratospheric ozone depletion. The seedlings grown under 10 % UV-B radiation showed an increase of 45 % net photosynthetic rate (PN) and 47 % stomatal conductance, while seedlings grown under 40 % UV-B radiation exhibited a decrease of 59 % PN with simultaneous elevation of 73 % intercellular CO2 concentration. Effects of UV-B on contents of lipids, saccharides, amino acids, and proteins were significant only at high doses of UV-B radiation. The concentration of anthocyanin was reduced with increasing doses of UV-B. The reverse was true with phenols and flavonoids.     

云杉种子萌发和幼苗生长对气候变暖与UV B辐射增强的响应

采用开顶式有机玻璃罩(OTCs)及紫外灯分别模拟气候变暖和UV-B增强,对位于气候变暖和UV-B增强突出的青藏高原东缘的高山峡谷地云杉种子萌发、幼苗生长和光合色素含量的变化进行测定分析,探讨云杉对气候变暖和UV-B增强的响应机理。结果显示:(1)UV-B辐射增强对云杉种子萌发无显著影响,但显著抑制萌发幼苗的生长、降低其针叶叶绿素含量,并造成幼苗大量死亡(P<0.05)。(2)气候变暖使云杉种子提前萌发,并提高了发芽势、发芽率和发芽指数,促进幼苗生长和叶绿素的积累,显著降低幼苗死亡率(P<0.05)。(3)气候变暖缓解了UV-B增强对云杉萌发幼苗生长和叶绿素含量的抑制作用,并降低了UV-B胁迫下幼苗的死亡率。研究表明,在未来气候变暖和UV-B辐射增强同时存在时,气候变暖能够在一定程度上缓解UV-B增强对云杉林早期更新带来的抑制作用。     

干旱胁迫下CO2浓度升高对转StAPX番茄植株耐旱能力的影响

在干旱胁迫伴随大气CO2浓度以及升高的CO2浓度（加倍）条件下,以过量表达番茄类囊体膜抗坏血酸过氧化物酶基因（StAPX）的转基因番茄为试材,探明干旱胁迫TCO2浓度升高对转基因及其野生型番茄植株清除活性氧及耐旱能力的影响。结果表明：升高的CO2浓度明显增加了干旱胁迫下植物的光合水平;升高的CO2浓度明显降低了干旱导致的植物体内H2O2．和O2的积累,影响了干旱胁迫下番茄植株的水．水循环系统的活性氧清除酶活性和小分子抗氧化物质含量;干旱胁迫下即使伴随升高的CO2浓度,测试番茄植株体内的渗透调节物质含量变化也不太明显;升高的CO2浓度明显降低了干旱胁迫下的植物细胞膜伤害程度;干旱胁迫下,升高的CO2浓度对转基因番茄株系比对野生型植株的影响更加明显。结果证明干旱逆境下,升高的CO2浓度能够在一定程度上进一步提高转基因番茄植株的耐旱性。     

Modulated increased UV-B radiation affects crop growth and grain yield and quality of maize in the field

Current research on the effect of increased UV-B radiation on crop production has been limited to exposing plants to improbable UV-B dose or growth condition. The objective of this study was to test the effects of short-term modulated increased UV-B radiation on maize (Zea mays L.) growth, grain yield, and quality under field conditions for three years. A modulated irradiance system was used to maintain UV-B radiation at 30% above the ambient level and was applied daily between the elongation and silking stages of maize. The result indicated that increased UV-B radiation adversely affected maize growth and yield, especially on plant height when UV-B was enhanced at the elongation stage and on yield when UV-B was enhanced near the silking stage. Yield reduction that induced by enhanced UV-B radiation was associated with reductions in number of kernels per row and kernel mass. Protein content of grains was increased with enhanced UV-B radiation, but oil and starch contents were not affected. This study confirmed the sensitivity of maize to increased UV-B radiation under the field condition, and contributed to understand the full negative and positive effects of increased UV-B radiation on crop production.     

UV－B辐射增强对长白山五种藓类植物生长的影响

对生长在中国长白山的5种藓类植物——垂枝藓、拟垂枝藓、塔藓、星塔藓和高山金发藓分别以辐射强度为0.2(自然光照,对照)、3.0(紫外线中等辐射强度)和6.0kJ.m-2.d-1(高剂量辐射强度)的UV-B照射40d后,测定其株高、生物量及叶绿素含量.结果表明:中等和高强度的UV-B辐射使拟垂枝藓和塔藓的株高、生物量和叶绿素含量分别下降了32.3%、62.4%、81.3%和21.4%、59.4%、62.8%,其相对生长速率均为负值;高剂量UV-B辐射处理下垂枝藓的生物量稍有上升,而高山金发藓地下部分的生物量增加1倍,但叶绿素含量变化不明显.高山金发藓和垂枝藓抵抗UV-B辐射的能力较强,拟垂枝藓和塔藓对UV-B辐射较敏感.     

The combined effects of CO2 concentration and solar UV-B radiation on faba bean grown in open-top chambers

The response of faba bean seedlings to the combined effects of increased atmospheric CO2 concentrations ([CO2]) and solar UV-B irradiance was studied using open-top chambers transparent to UV-B radiation. The purpose of the study was to determine whether effects of increased [CO2] on growth and physiology are modified by the present solar UV-B fluence rate in the Netherlands. Seedlings were exposed to 350 or 700 micromoles mol-1 CO2. At both [CO2], solar UV-B irradiance was either present or reduced using polyester foil opaque to UV-B radiation. To obtain information on the time dependence of increased [CO2] and UV-B radiation effects, three harvests were performed during the experiment. CO2 enrichment resulted in increased biomass production at all harvests. At the final harvest, UV-B radiation did not affect biomass production but a significant decrease was observed after 14 d of treatment. A reduction of the UV-B fluence increased shoot length at both [CO2] throughout the experiment. UV-B radiation slightly altered biomass allocation. Plants grown at reduced levels of UV-B radiation invested less biomass in flowers and more in stem material compared to plants grown at ambient UV-B levels. CO2 enrichment resulted in a stimulation of net photosynthesis after 26 and 38 d of treatment. UV-B reduction did not alter this response. After 26 d of treatment, photosynthetic acclimation to CO2 enrichment was observed, which was probably the result of accumulation of carbohydrates in the leaves. After 38 d, photosynthetic acclimation was no longer present. The UV absorbance of methanolic leaf extracts was increased by CO2 enrichment only. Both CO2 enrichment and solar UV-B reduced the transmittance of radiation through intact attached leaves. Interaction between [CO2] and UV-B radiation was limited to UV-A transmittance of leaves. Under prevalent experimental conditions, UV-B radiation did not affect the measured physiological parameters. Most open-top chambers used for climate change research are constructed of materials which do not transmit UV-B radiation. Our results indicate that part of the 'chamber effects' on plant height often described in the literature might be explained by the absence of solar UV-B radiation in these chambers.     

Enhanced UV-B radiation has little effect on growth, δ13C values and pigments of pot-grown rice (Oryza sativa) in the field

Predicted increase in ultraviolet-B (UV-B: 280–320 mn) radiation may have adverse impacts on growth and yield of rice ( Oryza sativa L.), as has been found in studies hitherto. However, most of the studies were conducted in growth chambers or greenhouses where the plants are generally more sensitive to UV-B than in the field, presumably because of the distorted balance between UV-B and ultraviolet-A as well as PAR. This study was conducted to address the effects of enhanced UV-B on growth and yield of rice under a realistic spectral balance in the field. Three cultivars, "Koshihikari",'IR 45'and'IR 74'were pot-grown and irradiated with enhanced UV-B for most of the growing season in the field at Tsukuba, Japan (36°01'N, 140°07'E). The UV-B enhancement simulated ca 38% depletion of stratospheric ozone at Tsukuba. The results showed no UV-B effects on plant height, numbers of tillers and panicles, dry weight of the plant parts or the grain yield for any of the 3 cultivars. Natural abundance of ¹³C in the flag leaves was not altered by the UV-B enhancement either. While UV-absorbing compounds showed no response to the UV-B enhancement, chlorophyll contents decreased with enhanced UV-B. However, the decrease of chlorophyll was limited to an early growth stage with no effect later. We thus found no extraordinary impact of the nearly doubled UV-B radiation on rice in the field, and it would appear that a reliable prediction of the effects of UV-B will require experiments carried out over a number of years under various climatic and solar UV-B regimes.     

Influence of Ultraviolet Radiation on Germination and Early Seedling Growth

The influence of UV-B radiation (280–320 nm) from filtered and unfiltered FS-40 fluorescent sunlamps on germination and early seedling growth was examined for a range of vegetables (tomato, radish, cucumber, lettuce, and bean) and field crops (wheat, cotton, soybean, and millet). Continuous exposure of seeds for 3 days to 26.9 × 10⁻² W × m⁻² UV-B radiation (280–320 nm) at 25°C, had a slight effect on fresh weight of seedlings but no appreciable influence on germination percentage, or dry weight of seedlings. Extending the time of exposure to 6 days, however, resulted in abnormal seedling growth in all species but wheat. Typical responses were short, stubby roots, bronzing of the cotyledons, increased pigmentation, and abnormal curvature of the shoots.     

Effects of enhanced UV-B radiation on the hormonal content of vegetative and reproductive tissues of two tomato cultivars and their relationships with reproductive characteristics

The effects of enhanced UV-B radiation on hormone changes in vegetative and reproductive tissues of tomato (Lycopersicon esculentum Mill.) and their relationships with reproductive characteristics were studied. Two cultivars, TongHui (TH) and XiaGuang (XG), were grown in the field for one growing season under ambient (Control), ambient plus 2.54 kJ m^–2 d^–1 (T1) or ambient plus 4.25 kJ m^–2 d^–1 (T2) of supplemental ultraviolet-B (280–320 nm). The number of open flowers increased significantly in the TH cultivar under T2 while it declined in the XG cultivar under T1. Although pollen germination from both cultivars was inhibited by UV-B treatment, fruit number was enhanced in the TH cultivar at both UV-B doses and in the XG cultivar at the low dose. On the other hand, seed size (dry weight) was reduced in the XG cultivar by both UV-B doses and in the TH cultivar at the low UV-B dose. The final germination rates of seeds from control and UV-B treated plants of both cultivars showed no significant differences (p > 0.05), while germination was delayed in the TH cultivar at both doses of UV-B and in the XG cultivar only for T2. To determine the mechanism of UV-B's effects on developmental processes, hormone concentrations in leaves, pistils and seeds were analyzed using ELISA on partially purified extracts. The results suggested that enhanced UV-B radiation induced hormone changes in both vegetative and reproductive tissues. The alteration of flower number may be associated with the changes of ZR in leaves under enhanced UV-B radiation and the delayed germination may due to the changes in seed ABA and GAs.     

Effect of seed pretreatment by magnetic field on the sensitivity of cucumber (Cucumis sativus) seedlings to ultraviolet-B radiation

The effects of seed pretreatment by magnetic field (MF) on the impacts of ultraviolet-B (UV-B) radiation were tested using cucumber (Cucumis sativus) seedlings in phytotron. Soaked cucumber seeds were placed in MF of various strengths (0, 0.2 and 0.45 T). After germination the seeds were sowed in homogeneous garden soil and grown, then cucumber seedlings were exposed to 0 (as control) and 3.5 kJ m⁻² UV-B irradiation, respectively. Some effects of UV-B radiation and MF-pretreatment as well as their combination were investigated. MF-pretreatment increased seed germination rate, seedling growth and development, although also increased lipid oxidation and ascorbic acid contents. On the other hand, our results provided evidence that seed MF-pretreatment increased the sensitivity of cucumber seedlings to UV-B radiation. The seedling growth and development were significantly decreased by the combination of UV-B irradiation and MF-pretreatment. This combination also increased oxidative pressure and decreased actual quantum yield of PS II. Leaf UV-B absorbing compound was increased by MF-pretreatment or UV-B irradiation, whereas their combination significantly decreased it. These results suggested that the harmful effects of combination were partially due to the inhibition of secondary metabolism.     

Leaf and canopy photosynthetic characteristics of cotton (Gossypium hirsutum) under elevated CO2 concentration and UV-B radiation

Increases in both atmospheric CO2 concentration ([CO2]) and ultraviolet-B (UV-B) radiation on the Earth's surface are features of current climate change patterns. An experiment was conducted in sunlit, controlled environment chambers known as Soil-Plant-Atmosphere-Research (SPAR) units to determine interactive effects of elevated [CO2] and UV-B radiation on leaf and canopy photosynthetic characteristics of cotton. Six treatments were comprised of two CO2 levels of 360 (ambient) and 720 (elevated) microL L(-1) and three levels of 0 (control), 8, and 16 kJ m(-2) d(-1) biologically effective UV-B radiation. Treatments were imposed for 66 days from crop emergence through three weeks after the first flower stage. Plants grown in elevated [CO2] had significantly greater leaf area, higher leaf and canopy net photosynthetic rates (PN), lower dark respiration rate (Rd), and lower light compensation point (LCP) than plants grown in ambient [CO2]. There was no difference in CO2 compensation point (gamma), maximum rate of Rubisco activity (Vcmax), or light-saturated rate of electron transport (Jmax) between ambient and elevated CO2 treatments. When plants were grown in 8 kJ m(-2) d(-1) UV-B radiation, most of the measured photosynthetic parameters did not differ from control plants. High UV-B (16 kJ) radiation, however, caused 47-50% smaller leaf area, 38-44% lower leaf PN, 72-74% lower Vcmax, and 61-66% lower Jmax compared to the control. There were no interactive effects of [CO2] and UV-B radiation on most of the photosynthetic parameters measured. From the results, it is concluded that decreased canopy photosynthesis due to enhanced UV-B radiation in cotton is associated with both smaller leaf area and lower leaf PN, and loss of Rubisco activity and electron transport are two major factors in UV-B inhibition of leaf PN.     

UV-B Radiation Suppresses the Growth and Antioxidant Systems of Two Marine Microalgae, Platymonas subcordiformis (Wille) Hazen and Nitzschia closterium (Ehrenb.) W. Sm

This study investigated whether increased solar UV-B radiation (280-315 nm) could suppress the growth of marine microalgae through effects on their antioxidant systems. Two marine microalgae species, Platymonas subcordiformis (Wille) Hazen and Nitzschia closterium (Ehrenb.) W. Sm, were exposed to a range of UV-B radiation and both showed reductions in their growth rates, and the chlorophyll a (Chl a) and carotenoid (Car) contents when UV-B radiation dose increased. Superoxide anion radical (O2)production and the concentration of hydrogen peroxide (H2O2) and malodiadehyde (MDA) also increased with the increasing of UV-B radiation. Antioxidant systems, non-enzymic components (Car and glutathione content) and enzymic components (superoxide dismutase (SOD) and catalase (CAT) activity), decreased as a result of enhanced UV-B radiation. When the exogenous glutathione (GSH) was added, the effects of UVB radiation on the growth of the two species were alleviated. These results suggest that enhanced UV-B radiation suppressed the antioxidant systems and caused some active oxygen species to accumulate, which in turns retarded the development of the marine microalgae.     

The effects of ultraviolet-B radiation on loblolly pine. I. Growth, photosynthesis and pigment production in greenhouse-grown seedlings

One-year old loblolly pine ( Pinus taeda L.) seedlings were grown in an unshaded greenhouse for 7 months under 4 levels of ultraviolet-B (UV-B) radiation simulating stratospheric ozone reductions of 16, 25 and 40% and included a control with no UV-B radiation. Periodic measurements were made of growth and gas exchange characteristics and needle chlorophyll and UV-B-absorbing-compound concentrations. The effectiveness of UV-B radiation on seedling growth and physiology varied with the UV-B irradiance level. Seedlings receiving the lowest supplemental UV-B irradiance showed reductions in growth and photosynthetic capacity after only 1 month of irradiation. These reductions persisted and resulted in lower biomass production, while no increases in UV-B-absorbing compounds in needles were observed. Seedlings receiving UV-B radiation which simulated a 25% stratospheric ozone reduction showed an increase in UV-B-absorbing-compound concentrations after 6 months, which paralleled a recovery in photosynthesis and growth after an initial decrease in these characteristics. The seedlings grown at the highest UV-B irradiance (40% stratospheric ozone reduction) showed a more rapid increase in the concentration of UV-B-absorbing compounds and no effects of UV-B radiation on growth or photosynthetic capacity until after 4 months at this irradiance. Changes in photosynthetic capacity were probably the result of direct effects on light-dependent processes, since no effects were observed on either needle chlorophyll concentrations or stomatal conductance. Further studies are necessary to determine whether these responses persist and accumulate over subsequent years.     

Effects of increasing UV-B radiation and atmospheric CO2 on photosynthesis and growth: implications for terrestrial ecosystems

Increases in UV-B radiation reaching the earth as a result of stratospheric ozone depletion will most likely accompany increases in atmospheric CO₂ concentrations. Many studies have examined the effects of each factor independently, but few have evaluated the combined effects of both UV-B radiation and elevated CO₂. In general the results of such studies have shown independent effects on growth or seed yield. Although interspecific variation is large, high levels of UV-B radiation tends to reduce plant growth in sensitive species, while CO₂ enrichment tends to promote growth in most C₃ species. However, most previous studies have not looked at temporal effects or at the relationship between photosynthetic acclimation to CO₂ and possible photosynthetic limitations imposed by UV-B radiation. Elevated CO₂ may provide some protection against UV-B for some species. In contrast, UV-B radiation may limit the ability to exploit elevated CO₂ in other species. Interactions between the effects of CO₂ enrichment and UV-B radiation exposure have also been shown for biomass allocation. Effects on both biomass allocation and photosynthetic acclimation may be important to ecosystem structure in terms of seedling establishment, competition and reproductive output. Few studies have evaluated ecosystem processes such as decomposition or nutrient cycling. Interactive effects may be subtle and species specific but should not be ignored in the assessment of the potential impacts of increases in CO₂ and UV-B radiation on plants.     

Senescence and hyperspectral reflectance of cotton leaves exposed to ultraviolet-B radiation and carbon dioxide

The objectives of this study were to determine the effects of UV-B radiation and atmospheric carbon dioxide concentrations ([CO(2)]) on leaf senescence of cotton by measuring leaf photosynthesis and chlorophyll content and to identify changes in leaf hyperspectral reflectance occurring due to senescence and UV-B radiation. Plants were grown in controlled-environment growth chambers at two [CO(2)] (360 and 720 micro mol mol(-1)) and three levels of UV-B radiation (0, 7.7 and 15.1 kJ m(-2) day(-1)). Photosynthesis, chlorophyll, carotenoids and phenolic compounds along with leaf hyperspectral reflectance were measured on three leaves aged 12, 21 and 30 days in each of the treatments. No interaction was detected between [CO(2)] and UV-B for any of the measured parameters. Significant interactions were observed between UV-B and leaf age for photosynthesis and stomatal conductance. Elevated [CO(2)] enhanced leaf photosynthesis by 32%. On exposure to 0, 7.7 and 15.1 kJ of UV-B, the photosynthetic rates of 30-day-old leaves compared with 12-day-old leaves were reduced by 52, 76 and 86%, respectively. Chlorophyll pigments were not affected by leaf age at UV-B radiation of 0 and 7.7 kJ, but UV-B of 15.1 kJ reduced the chlorophylls by 20, 60 and 80% in 12, 21 and 30-day-old leaves, respectively. The hyperspectral reflectance between 726 and 1142 nm showed interaction for UV-B radiation and leaf age. In cotton, leaf photosynthesis can be used as an indicator of leaf senescence, as it is more sensitive than photosynthetic pigments on exposure to UV-B radiation. This study revealed that, cotton leaves senesced early on exposure to UV-B radiation as indicated by leaf photosynthesis, and leaf hyperspectral reflectance can be used to detect changes caused by UV-B and leaf ageing.