紫外辐射增加对植物生长及某些生理代谢的影响

本文就紫外线辐射增加对植物生长发育、生理特性和作物产量等方面的影响进行了论述。     

Effects of ultraviolet-B radiation on the growth and yield of crop plants

This paper reviews growth chamber, greenhouse, and field studies on the effects of ultraviolet-B (UV-B. between 280 and 320 nm) radiation on agricultural crop plants. Our understanding of the physiological effects of UV-B radiation comes primarily from growth chamber studies, where UV-B is artificially supplied via filtered lamps. Both photosystems I and II, as well as carboxylating enzymes, are sensitive to UV-B radiation. Ultraviolet-B radiation also affects stomatal resistance, chlorophyll concentration, soluble leaf proteins, lipids, and carbohydrate pools. In general, the effects of UV-B radiation are accentuated by the low levels of visible radiation typically found inside growth chambers. Ultraviolet-B radiation has also been shown to affect anatomical and morphological plant characteristics. Commonly observed UV-B induced changes include plant stunting, reductions in leaf area and total biomass, and alterations in the pattern of biomass partitioning into various plant organs. In sensitive plants, evidence of cell and tissue damage often appears on the upper leaf epidermis as bronzing, glazing, and chlorosis. Epidermal transmission in the UV region decreases in irradiated leaves. This decrease is primarily associated with a stimulation in flavonoid biosynthesis and is thought to be a protective, screening response to the deleterious effects of UV-B. A considerable degree of variability exists in sensitivity to UV-B radiation between different species. Approximately 30% of the species tested were resistant, another 20% were extremely sensitive, and the remainder were of intermediate sensitivity, in terms of reductions in total dry weight. In addition to this sizable interspecific variability, there appears to be a similarly wide intraspecific variability in UV-B response. The effects of UV-B radiation on crop yield have only been examined in a limited number of field studies, with ambient levels of UV-B radiation being supplemented with fluorescent sun lamps. Due to various deficiencies, all these field experiments to date have only limited utility for assessing the potential impact of enhanced levels of UV-B on crop productivity.     

Multiple switches between vegetative and reproductive growth in annual plants

A model of growth and reproduction in annual plants was developed by Cohen (1971, J. Theor. Biol.33, 299–307) to determine the allocation strategy which maximizes seed yield. The model divides the plant into vegetative and reproductive parts and predicts that yield is maximized by a strategy consisting of a switch from purely vegetative to strictly reproductive growth. We generalize Cohen's model to include vegetative and reproductive loss terms. Both growth and loss rates are allowed to vary with time. Using optimal control theory we find that seed yield is maximized by a strategy consisting of multiple switches between vegetative and reproductive growth, for certain ranges of the model parameters. In natural systems a predictable vegetative loss burst may be necessary to promote multiple switches.     

Effects of UV-B radiation on photosynthesis and growth of terrestrial plants

The photosynthetic apparatus of some plant species appears to be well-protected from direct damage from UV-B radiation. Leaf optical properties of these species apparently minimizes exposure of sensitive targets to UV-B radiation. However, damage by UV-B radiation to Photosystem II and Rubisco has also been reported. Secondary effects of this damage may include reductions in photosynthetic capacity, RuBP regeneration and quantum yield. Furthermore, UV-B radiation may decrease the penetration of PAR, reduce photosynthetic and accessory pigments, impair stomatal function and alter canopy morphology, and thus indirectly retard photosynthetic carbon assimilation. Subsequently, UV-B radiation may limit productivity in many plant species. In addition to variability in sensitivity to UV-B radiation, the effects of UV-B radiation are further confounded by other environmental factors such as CO₂, temperature, light and water or nutrient availability. Therefore, we need a better understanding of the mechanisms of tolerance to UV-B radiation and of the interaction between UV-B and other environmental factors in order to adequately assess the probable consequences of a change in solar radiation.Abbreviations A_max light and CO₂ saturated rate of oxygen evolution - Ci internal CO₂ concentration - F_v/F_m ratio of variable to total fluorescence yield - PAR photosynthetically active radiation (400–700 nm) - PS II Photosystem II - _app apparent quantum yield of photosynthesis - SLW specific leaf weight - UV-B ultraviolet-B radiation between 290–320 nm     

Influence of supplemental UV-B radiation on photosynthetic characteristics of rice plants

In a field experiment with rice (Oryza sativa L. cv. Saket 4) grown under ambient and supplemental ultraviolet-B (UV-B) radiation at 20 % ozone depletion, differences in gas exchange, concentrations of photosynthetic pigments, anthocyanins and flavonoids, biomass accumulation, catalase and peroxidase activities, and contents of ascorbic acid and phenol were determined. Decline in photosynthesis was associated with reductions in stomatal conductance and concentrations of photosynthetic pigments. Enhanced UV-B radiation (eUV-B) increased the contents of flavonoid and phenolic compounds in leaves. Peroxidase activity increased and catalase activity was always lower at eUV-B. The total plant biomass decreased at eUV-B.     

Influence of supplemental UV-B radiation on photosynthetic characteristics of rice plants

In a field experiment with rice (Oryza sativa L. cv. Saket 4) grown under ambient and supplemental ultraviolet-B (UV-B) radiation at 20 % ozone depletion, differences in gas exchange, concentrations of photosynthetic pigments, anthocyanins and flavonoids, biomass accumulation, catalase and peroxidase activities, and contents of ascorbic acid and phenol were determined. Decline in photosynthesis was associated with reductions in stomatal conductance and concentrations of photosynthetic pigments. Enhanced UV-B radiation (eUV-B) increased the contents of flavonoid and phenolic compounds in leaves. Peroxidase activity increased and catalase activity was always lower at eUV-B. The total plant biomass decreased at eUV-B.     

Influence of cocksfoot streak virus on the growth of single cocksfoot plants

Healthy and streak-virus-infected cocksfoot plants of a single genotype were examined over a 2-year period. In the first year infection decreased tillering by about 40%, but in pot-grown plants individual tiller weights were 30% higher so dry-matter yield was decreased by only 10%. In the second year the larger tiller weights compensated completely for decreased tillering. No similar compensation was observed in field-grown plants. The virus had the largest effects when soil fertility was highest, healthy plants producing significantly greater responses to nitrogen effects, but potassium, at certain times of the year, produced larger tiller weights in infected than in healthy plants. Infection decreased dry-matter yield more in frequently than in infrequently cut plants. Infection greatly decreased the number of vegetative but not of fertile tillers. Infected plants tended to flower earlier and produced fewer, slightly smaller, viable seeds.     

Small variance in growth rates in annual plants has large effects on genetic drift

? Premise of the Study: Effective population size (N(e)) is a critical index of the evolutionary capacity of populations. Low N(e) indicates that standing genetic diversity is susceptible to loss via stochastic processes (and inbreeding) and is, therefore, unavailable for natural selection to act upon. Reported N(e) in plant populations is often quite low. What biological and ecological factors might produce such low N(e) ? Methods: We conducted a simulation model to test the effect of randomly assigned and autocorrelated growth rates of annual plants on plant-size distributions at the end of the growing season. Because plant size is directly correlated with reproductive output in annual plants, variation in plant size reflects variation in reproduction, and thus our modeled size distributions can be used to estimate N(e). ? Key Results: Randomly assigned growth rates had a negligble effect on N(e)/N. Autocorrelated growth rates decreased N(e)/N as the length of the growing season increased. This was the case even when the variance in growth rates was as low as 0.1% of the mean. ? Conclusions: While intrinsic plant biology can affect the degree of growth autocorrelation, ecological factors such as competition, herbivory, and abiotic stress can increase or decrease levels of growth autocorrelation. Ecological factors that increase growth autocorrelation can have significant effects on genetic drift within populations.     

Influence of UV-B radiation on the reproductive function of Hordeum vulgare L. plants

Irradiation of barley seedlings by ultraviolet-B radiation influences the growth and development of the sexual elements of the spike, accelerating differentiation of the sporogenous tissue of the anther and the male gametophyte, a phenomenon which is accompanied by an increase in the asynchronicity of microgametogenesis and in heterogeny of the pollen grains, and in an increase in the sterility of the pollen grains. High ultraviolet doses tend to reduce the level of sterility of the anther due to intensification of haplontic cell selection. The influence of ultraviolet irradiation on the reproductive system of the plant is expressed in genotoxic (through damage to the DNA of meristemic cells) and photo-inductive (through acceleration of efflorescence and differentiation of gametophytes) effects.     

Influence of UV-B radiation on young triticale plants with different wax cover

Ultraviolet-B radiation (biologically effective dose 2.6 kJ m⁻² d⁻¹) had negative influence on morphology and physiology of the young triticale plants. Plants exposed to UV-B were of lower height than control plants, their leaves were narrow, and the rate of net photosynthesis was decreased. The line RAH 336, which wax cover is lesser than that of traditional cultivar Magnat, was more susceptible to UV-B radiation, considering primary photosynthesis reactions, recorded by chlorophyll a fluorescence. An activation of protective mechanisms was observed: plants responded to UV-B by an increase of the content of UV-B absorbing compounds, and changes of antioxidant enzyme activities.     

Effect of ultraviolet radiation on chlorophyll,carotenoid, protein and proline contents of some annual desert plants

Investigation was carried out to find whether enhanced ultraviolet radiation influences the Malva parviflora L., Plantago major L., Rumex vesicarius L. and Sismbrium erysimoids Desf. of some annual desert plants. The seeds were grown in plastic pots equally filled with a pre-sieved normal sandy soil for 1 month. The planted pots from each species were randomly divided into equal groups (three groups). Plants of the first group exposed to white-light tubes (400–700 nm) 60 w and UV (365 nm) 8 w tubes. The second group was exposed to white-light tubes (400–700 nm) 60 w and UV (302 nm) 8 w tubes. The third group was exposed to white-light tubes (400–700 nm) 60 w and UV (254 nm) 8 w tubes, respectively, for six days. The results indicated that the chlorophyll contents were affected by enhanced UV radiation. The chlorophyll a, b, and total contents were decreased compared with the control values and reduced with the enhanced UV radiation, but the carotenoid was increased compared with the control and also reduced with the enhanced UV radiation. So, the contents of chlorophylls varied considerably. M. parviflora showed the highest constitutive levels of accumulated chlorophyll a, b, and total chlorophyll (0.463, 0.307 and 0.774 mg g⁻¹ f w) among the investigated plant species. P. major showed the lowest constitutive levels of the chloroplast pigments, 0.0036, 0.0038 and 0.0075 mg g⁻¹ f w for chlorophyll a, b, and total chlorophyll at UV-365 nm, respectively. The protein content was decreased significantly in both root and shoot systems compared with the control values but, it was increased with increasing wave lengths of UV-radiation of all tested plants. R. vesicarius showed the highest protein contents among the investigated plants; its content was 3.8 mg g⁻¹ f w at UV-365 nm in shoot system. On the other hand, decreasing ultraviolet wave length induced a highly significant increase in the level of proline in both root and shoot of all tested plants. From the results obtained, it is suggested that proline can protect cells against damage induced by ultraviolet radiation. Statistically, the variations of the studied metabolic activities were significant due to UV radiation treatment in shoot and root system of all investigated plant species.     

Influence of growth retardants on the internode and ethylene production of sunflower plants

The growth-retarding activity of the norbornenodiazetine tetcyclacis and the di-oxanylalkenyl triazole LAB 150 978 as well as the ethylene-forming compounds 2-chloroethyl-phosphonic acid (ethephon) and 1-amino-cyclopropane-l-carboxylic acid (ACC) on stem histogenesis and ethylene production of sunflower plants ( He-lianthus annuus L. cv.Spanners Allzweck) has been studied. The shoot growth of plants hydroponically grown and treated was reduced by the compounds. The shortening in the length of the 1st internode caused by tetcyclacis and LAB 150 978 was mainly induced by inhibition of cell division (the internode possessed fewer cortical cells per cell file). In contrast, ethephon and ACC decreased internode elongation mainly by reducing the rate of cell enlargement.
The ethylene production of sunflower seedlings cultivated on agar nutrient medium rose with increasing concentrations of ethephon and ACC, the shoot length of the plants being progressively reduced.
Tetcyclacis and LAB 150 978 inhibited both the formation of ethylene and shoot growth. It is suggested that in contrast to ethephon and ACC, tetcyclacis and LAB 150 978 do not achieve their growth-retarding effect by influencing the production of ethylene.     

Effects of nitrogen amendment on annual plants in the Chihuahuan Desert

Effects of nitrogen amendments on spring annual plant distribution, primary production, and species diversity in a semi-arid environment were studied. The ecological responses of spring annual plant species to nitrogen differed between species, and between sites. The distribution of each species in a control transect was wider than in a nitrogen-treated transect. Annual plant species diversity at each station in the control transect was higher than that of the nitrogen-treated transect. The lower site of the Lower Basin Slope areas had the highest species diversity (0.94 for the control and 0.84 for the nitrogen-treated), and the Upper Basin Slope area, shrub vegetation zone, had the lowest species diversity (0.27 for the control and 0.05 for the nitrogen-treated) in both transects. Inorganic nitrogen in the nitrogen-treated transect soils was consistently higher than that in the control transect soils; however, the former showed more fluctuation from station to station than the latter. Above-ground biomass of spring annual plants in the nitrogen-treated transect was consistently higher than that in the control at each station. The maximum above-ground biomass in the control and nitrogen-treated transect was 24.4±4.4 gm⁻² and 61.2±10.6 gm⁻², respectively. Variations in above-ground biomass along the transect did not parallel with the variation in inorganic nitrogen in soils and species diversity.     

Influence of potassium concentration on growth and potassium uptake by rice plants

Summary Rice plants (Oryza sativa L.) were grown for 125 days in nutrient solutions maintained at constant potassium concentrations over the rate 51 to 1534 M. Data are recorded at different growth stages for relative growth rate, potassium content, absorption rate of this element per gram dry weight of roots per day and its utilization in dry-matter production. Optimum concentration for maximum growth was found to be about 256 M or 10 ppm potassium. Growth was more or less constant beyond this concentration. The maximum growth was characterized by a certain relative absorption rate (I_M) for maximum growth ranging from 106 to 757 g-atom of potassium per g dry weight of roots per day, during the period of cultivation. In general the content of this element in tops as a percentage of the total content does not change appreciably either under different concentrations or at different ages. When the concentration of the solution increased, the utilization of potassium (dry-matter production per unit element content) decreased. The ratio between the relative growth rate (RGR) and relative absorption rate (I_M) for maximum growth of rice ranged 1.4 during the first phase of growth to 1.3 at maturity of the crop. Higher ratios indicate an insufficient nutrient supply, lower ratios, however, either an abundant supply or a depressing effect of the solution on growth.     

Effects of grazing on diversity of annual plants in the Sonoran Desert

Summary A two-yar survey of winter-germinating annual plants in southern Arizona indicates that species diversity declines consistently as a function of increasingly recent grazing by cattle. This finding conflicts with reports that predators enhance prey species diversity in some marine and terrestrial systems. Consideration of equilibrium and nonequilibrium models suggests, however, that enhanced diversity should occur only for open, multi-celled prey populations experiencing intermittant predation. These general conditions appear not to hold for the cattle-annual plant system.     

Effects of the soil microbiome on the demography of two annual prairie plants

1. Both mutualistic and pathogenic soil microbes are known to play important roles in shaping the fitness of plants, likely affecting plants at different life cycle stages.
2. In order to investigate the differential effects of native soil mutualists and pathogens on plant fitness, we compared survival and reproduction of two annual tallgrass prairie plant species (Chamaecrista fasciculata and Coreopsis tinctoria) in a field study using 3 soil inocula treatments containing different compositions of microbes. The soil inocula types included fresh native whole soil taken from a remnant prairie containing both native mutualists and pathogens, soil enhanced with arbuscular mycorrhizal (AM) fungi derived from remnant prairies, and uninoculated controls.
3. For both species, plants inoculated with native prairie AM fungi performed much better than those in uninoculated soil for all parts of the life cycle. Plants in the native whole prairie soil were either generally similar to plants in the uninoculated soil or had slightly higher survival or reproduction.
4. Overall, these results suggest that native prairie AM fungi can have important positive effects on the fitness of early successional plants. As inclusion of prairie AM fungi and pathogens decreased plant fitness relative to prairie AM fungi alone, we expect that native pathogens also can have large effects on fitness of these annuals. Our findings support the use of AM fungi to enhance plant establishment in prairie restorations.

     

Influence of growth room and vessel humidity on the in vitro development of rose plants

An increase of the vapor pressure deficit (VPD) of the growth room atmosphere (from 600 Pa up to 2000 Pa) induced a variation in the air VPD inside the vessels used for rose micropropagation.During the photoperiod, the in vitro plants lost water by evaporation. During the night period, depending upon the VPD of the growth room, plants could take water from the vessel atmosphere.According to the intensity of the transpiration, large changes in the growth and morphology were observed: decrease in multiplication rate, modification of leaf colour and area, reduction of the elongation and changes of the level of axillary buds which grew.