Different growth sensitivity to enhanced UV-B radiation between male and female Populus cathayana

We investigated sex-related morphological and physiological responses to enhanced UV-B radiation in the dioecious species Populus cathayana Rehd. Cuttings were subjected to two UV-B radiation regimes: ambient (4.5 kJ m?2 day?1) and enhanced (12.5 kJ m?2 day?1) biologically effective UV-B radiation for one growing season. Enhanced UV-B radiation was found to significantly decrease the shoot height and basal diameter and to reduce the leaf area, dry matter accumulation, net photosynthesis rate (P(n)), chlorophyll a/b ratio (Chl a/b) and anthocyanin content. Enhanced UV-B radiation also increased chlorophyll pigment, leaf nitrogen, malondialdehyde and abscisic acid (ABA) content, superoxide dismutase and peroxidase activities and UV-B-absorbing compounds. No significant effects of enhanced UV-B radiation were found on biomass allocation, gas exchange (except for P(n)), photochemical efficiency of photosystem II or water use efficiency. Moreover, different sensitivity to enhanced UV-B radiation between males and females was detected. Under enhanced UV-B radiation, males exhibited significantly higher basal diameter and leaf nitrogen, and lower Chl a/b, ABA content, UV-B-absorbing compounds, as well as less decrement of leaf area and dry matter accumulation than did females. However, no significant sexual differences in these traits were found under ambient UV-B radiation. Our results suggest that males may possess a greater UV-B resistance than do females, with males having a more efficient antioxidant system and higher anthocyanin content to alleviate UV-B penetration stress than females.     

Growth, leaf anatomy, and physiology of Populus clones in response to solar ultraviolet-B radiation

We compared the physiological and morphological responses of rooted cuttings of Populus trichocarpa Torr. & Gray and P. trichocarpa x P. deltoides Bartr. ex Marsh. grown in either near-ambient solar ultraviolet-B (UV-B; 280-320 nm) radiation (cellulose diacetate film) or subambient UV-B radiation (polyester film) for one growing season. Midday biologically effective UV-B radiation was 120.6 and 1.6 mJ m(-2) s(-1) under the cellulose diacetate and polyester films, respectively. Gas exchange, leaf chlorophyll, light harvesting efficiency of photosystem II, and foliar UV-B radiation-absorbing compounds (i.e., flavonoid derivatives) were measured in expanding (leaf plastochron index (LPI) 5), nearly expanded (LPI 10), and fully expanded mature (LPI 15) leaves of intact plants of plastochron index 30 to 35. Plants were then harvested and height, diameter, biomass allocation and leaf anatomical attributes determined. Net photosynthesis, transpiration, and stomatal conductance were significantly greater in mature leaves exposed to subambient UV-B radiation than in mature leaves exposed to near-ambient UV-B radiation. Concentrations of UV-B radiation-absorbing compounds (measured as absorbance of methanol-extracts at 300 nm) were significantly greater in mature leaves exposed to near-ambient UV-B radiation than in mature leaves exposed to subambient UV-B radiation. The UV-B radiation treatments had no effects on chlorophyll content or intrinsic light harvesting efficiency of photosystem II. Height, diameter, and biomass were not significantly affected by UV-B radiation regime in either clone. Leaf anatomical development was unaffected by UV-B radiation treatment in P. trichocarpa x P. deltoides. For P. trichocarpa, leaf anatomical development was complete by LPI 10 in the near-ambient UV-B radiation treatment, but continued through to LPI 15 in the subambient UV-B radiation treatment. Mature leaves of P. trichocarpa were thicker in the subambient UV-B radiation treatment than in the near-ambient UV-B radiation treament as a result of greater development of palisade parenchyma tissue. We conclude that exposure to near-ambient UV-B radiation for one growing season caused shifts in carbon allocation from leaf development to other pools, probably including but not limited to, UV-B absorbing compounds. This reallocation curtailed leaf development and reduced photosynthetic capacity of the plants compared with those in the subambient UV-B radiation treatment and may affect growth over longer periods of exposure.     

杨树不同品种插穗自身含水量与扦插成活的关系

以中黑防、晚花杨、小黑杨14号3个杨树品种为试验材料,设计自然失水24 h、48 h、72 h三个梯度(处理)研究插穗自身含水量与扦插成活的关系.结果表明:在相同的自然失水时间里,晚花杨失水率最大,自然失水处理72 h,失水率可达30.7%,小黑杨14号为29.6%,中黑防也达到了27.9%.中黑防在穗条自身失水率达到30%时,生根与成活率才会显著下降;而小黑杨14号和晚花杨在穗条自身失水率达到20%时,生根与成活率就会显著下降.     

赤美杨选种试验研究

赤美杨是赤峰市林科院与中国林科院合作,以美洲黑杨为母本,以青杨为父本杂交获得F1代,经过在赤峰地区30多年不同立地条件、不同林种、不同密度栽培试验选育出的杂种后代.13年生赤美杨单株胸径最大达到46 cm,树高18.5 m,单株材积1.499 m3,平均材积生长量是对照品种小黑杨的213.8％.     

Accumulation of flavonoids and related compounds in birch induced by UV-B irradiance

A growth chamber experiment was conducted to examine the effects of UV-B exposure (4.9 kJ m(-2) day(-1) of biologically effective UV-B, 280-320 nm) on shoot growth and secondary metabolite production in Betula pendula (Roth) and B. resinifera (Britt.) seedlings originating from environments in Finland, Germany and Alaska differing in solar UV-B radiation and climate. Neither shoot growth nor the composition of secondary metabolites was affected by UV-B irradiance, but the treatment induced significant changes in the amounts of individual secondary metabolites in leaves. Leaves of seedlings exposed to UV-B radiation contained higher concentrations of several flavonoids, condensed tannins and some hydroxycinnamic acids than leaves of control seedlings that received no UV-B radiation. At the population level, there was considerable variation in secondary metabolite responses to UV-B radiation: among populations, the induced response was most prominent in Alaskan populations, which were adapted to the lowest ambient UV-B radiation environment. I conclude that solar UV-B radiation plays an important role in the formation of secondary chemical characteristics in birch trees.     

Responses to ultraviolet-B radiation by purely symbiotic and NO3-fed nodulated tree and shrub legumes indigenous to southern Africa

Purely symbiotic and NO3-fed nodulated seedlings of Virgilia oroboides (Bergius) T.M. Salter, Cyclopia maculata (L.) Vent and Podalyria calyptrata Willd. were exposed to biologically effective ultraviolet-B radiation (UV-B) to assess the effects of above- and below-ambient UV-B on growth, symbiotic function and metabolite concentrations. Seedlings were grown outdoors either on tables under ambient or 34 or 66% above-ambient UV-B conditions (UV-B100 control, UV-B134 and UV-B166, respectively), or in chambers providing below-ambient (22% of ambient) UV-B (UV-B22) along with a UV-A control and a photosynthetically active radiation (PAR) control. Exposure of seedlings to UV-B166 radiation reduced (P < or = 0.05) leaf and stem dry mass by 34 and 39%, respectively, in C. maculata, and reduced leaf nitrogen concentration (%N) by 12% in V. oroboides. Nodule %N in C. maculata and stem %N in P. calyptrata also decreased (P < or = 0.05) in response to UV-B22 radiation compared with the UV-A control, but not compared with the PAR control. Concentrations of flavonoids, soluble sugars and starch were unaltered by the UV-B treatments. Application of 1 mM NO3 to UV-B166-treated seedlings increased whole-plant dry mass of V. oroboides and P. calyptrata by 47 and 52%, respectively. Dry mass of organs, nodule %N and total N concentration of these species also increased with NO3 application. However, NO3 supply decreased (P < or = 0.05) nodule dry mass, stem %N and leaf %N as well as root and leaf anthocyanin concentrations in C. maculata. In terms of UV-B x N interactions, dry mass of stems, roots, nodules and total biomass of NO3-fed C. maculata seedlings were reduced, and nodule %N, total N and leaf anthocyanins were depressed by the UV-B134 and UV-B166 treatments relative to UV-B100-treated seedlings. Although we found that above-ambient UV-B had no effects on growth and symbiotic function of V. oroboides and P. calyptrata seedlings, feeding NO3 to these species increased (P < or = 0.05) seedling growth. In contrast, purely symbiotic C. maculata seedlings were sensitive to the UV-B166 radiation treatment, and adding NO3 further increased their sensitivity to both the UV-B134 and UV-B166 treatments.     

Drought inhibits photosynthetic capacity more in females than in males of Populus cathayana

We investigated sex-related photosynthetic responses to drought in the dioecious species, Populus cathayana Rehd. Plants were subjected to two watering regimes (100% and 30% of field capacity) in a semi-controlled environment. Drought significantly decreased leaf area (LA), total number of leaves (TNL), specific leaf area (SLA), relative water content, net photosynthetic rate (P(n)), transpiration (E), stomatal conductance (g(s)), intercellular CO(2) concentration (C(i)), light saturation point (L(SP)), apparent quantum yield (Phi), carboxylation efficiency (CE), light-saturated photosynthetic rate (P(max)), maximum efficiency of PSII (F(v)/F(m)) and maximum effective quantum yield of PSII (Yield), and increased the total chlorophyll concentration (TC), CO(2) compensation point (Gamma), non-photochemical quenching coefficient, peroxidase (POD) activity and carbon isotope composition (delta(13)C). Moreover, differences between males and females were detected in many of these responses. In the drought treatment, males exhibited significantly higher LA, TNL, TC, concentration of carotenoids (Caro), P(n), E, g(s), C(i), L(SP), Phi, CE, P(max), F(v)/F(m), photochemical quenching coefficient, POD activity and delta(13)C, but a lower SLA, chlorophyll a/b ratio, carotenoids/total chlorophyll ratio and Gamma than females. However, Caro, L(SP), Gamma, Phi, CE and POD activity were apparently associated with sex-related resource demands, because significant differences in these traits were detected between the sexes under well-watered conditions. Our results indicate that drought stress limits photosynthetic capacity more in females than in males.     

NAA处理对杨树茎插穗生根的作用

本文选择毛白杨和加拿大杨这两个插穗生根难易程度不同的树种为研究对象。试验再次证明,适度的萘乙酸(NAA)处理可提高插穗生根率。它的最明显的作用是促进茎插穗沾药部分愈伤组织的产生。高浓度的NAA处理促使插穗中物质过多调运到正在生长的愈伤组织中。这不仅影响到嫩茎的生长,而且不利于细胞再分化为根原基,甚至产生生理毒害作用。NAA处理的效果因扦插时期而异。NAA处理可较迅速地引起乙烯的释放,可提高细胞质膜透性,提高呼吸强度。经NAA处理过的插穗,经过冷藏可提高插穗含水率和过氧化物酶活性。高浓度NAA处理更大地提高质膜的透性,使膜受到伤害,并使细胞失水。     

沈阳市6种行道树对紫外辐射屏蔽效应的研究

应用便携式紫外辐照计测定银杏、银中杨、垂柳、垂榆、梓树和京桃6种行道树树冠及其单叶对紫外辐射的屏蔽效应。结果表明：各树种紫外线辐射强度的日变化呈倒＂U＂字型,绿叶屏蔽紫外辐射的效果要好于黄叶。6个树种均表现出良好的紫外辐射屏蔽功能,67%以上的紫外辐射被屏蔽,屏蔽效应大小依次为：京桃〉垂榆〉梓树〉银杏〉垂柳〉银中杨。     

Intraspecific variation in drought response of Populus cathayana grown under ambient and enhanced UV-B radiation

? The effects of drought, enhanced UV-B radiation and their combination on plant growth and physiological traits were investigated in a greenhouse experiment in two populations of Populus cathayana Rehder originating from high and low altitude in south-west China.

? In both populations, drought significantly decreased biomass accumulation and gas exchange parameters, including net CO₂ assimilation rate (A), stomatal conductance (g _s ), transpiration rate (E) and photosynthetic nitrogen use efficiency (PNUE). However, instantaneous water use efficiency (WUE _i ), transpiration efficiency (WUE _T ), carbon isotope composition (δ¹³C) and nitrogen (N) content, as well as the accumulation of soluble protein, UV-absorbing compounds and abscisic acid (ABA) significantly increased in response to drought. On the other hand, cuttings from both populations, when kept under enhanced UV-B radiation, showed very similar changes, as under drought, in all above-mentioned parameters.

? Compared with the low altitude population, the high altitude population was more tolerant to drought and enhanced UV-B, as indicated by the higher level of biomass accumulation, gas exchange, water-use efficiency, ABA concentration and UV-absorbing compounds.

? After one growing season of exposure to different UV-B levels and watering regimes, the decrease in biomass accumulation and gas exchange, induced by drought, was more pronounced under the combination of UV-B and drought. Significant interactions between drought and UV-B were observed in WUE _i , WUE_T, δ¹³C, soluble protein, UV-absorbing compounds, ABA and in the leaf and stem N, as well as in the leaf and stem C:N ratio.

? Our results showed that UV-B acts as an important signal allowing P. cathayana seedlings to respond to drought and that the combination of drought and UV-B may cause synergistically detrimental effects on plant growth.

     

黑龙江省西部半干旱区8种阔叶乔木主要生理参数的特征分析

采用Li-6400便携式光合测定系统对黑龙江省西部半干旱区8种阔叶乔木主要生理参数进行了观测（盆栽试验）与比较分析。结果表明：随着光强的梯度变化,各树种的主要生理参数表现出不同程度的差异;通过对这些参数的平均值进行系统聚类分析,结果为：银中杨、349柳、DN113杨属于高光合、中蒸腾、高水分利用效率树种,山新杨、109...     

青杨与几个黑杨派品种的杂交制种方法分析

以青杨为母本,分别以辽宁杨、33号杨和美洲黑杨为父本,采用4种不同的处理方法,得到青杨最佳的杂交组合处理方法：青杨×辽宁杨（父本与青杨高温失活花粉的混合花粉）、青杨×33号杨关（键母词本：青花杨粉;提杂取交液制蒙种导）、青杨×美洲黑杨（父本与小青杨3：1混合花粉）。     

Enhanced tolerance of photosynthesis to high-light and drought stress in Pseudotsuga menziesii seedlings grown in ultraviolet-B radiation

We investigated the effects of an ambient dose of ultraviolet-B (UV-B) radiation on chamber-grown Pseudotsuga menziesii var. glauca (Beissn.) Franco (Douglas-fir) seedlings, to determine if the presence of UV-B radiation in the growth light regime induces tolerance to environmental stresses such as high light and drought. Douglas-fir seedlings were grown without UV-B radiation or with 6 kJ m-2 day-1 of biologically effective UV-B, which is ambient for the intermountain regions of Idaho. Non-stressed seedlings grown with UV-B radiation had 35% lower seedling dry mass, 36% higher concentrations of UV-B absorbing compounds per unit leaf area, 30% lower stomatal frequencies, 25% lower light-saturated photochemical efficiencies of Photosystem II and 45% lower light-saturated stomatal conductance than non-stressed seedlings grown without UV-B radiation. After 4 days of high-light stress, seedlings grown with UV-B radiation had 32% higher light-saturated carbon assimilation rates (A(CO2)) than seedlings grown without UV-B radiation. After water was withheld from the seedlings for up to 15 days, seedlings grown with UV-B radiation had 50% higher A(CO2) and 40% higher seedling water potentials than seedlings grown without UV-B radiation. The results support the hypothesis that UV-B radiation can act as an environmental signal to induce tolerance to high-light and drought stress in Douglas-fir seedlings. Possible mechanisms for the enhanced stress tolerance are discussed.     

UV-B辐射对亚热带森林凋落叶分解的影响

采用分解袋法研究自然和UV-B辐射滤减2种环境下6种亚热带代表性树种(杉木、马尾松、木荷、香樟、青冈和甜槠)凋落叶的分解情况。结果表明:除个别分解阶段外,各树种凋落叶在2种UV-B辐射环境下的干质量剩余率均存在显著差异,且随着分解时间延长,差异逐渐加大;与对照相比,UV-B辐射滤减显著降低了6个树种凋落叶的分解速率(P<0.01),降幅为33.3%～69.6%,对香樟凋落叶分解的影响最小,对杉木凋落叶分解的影响最大;UV-B辐射处理和凋落物类型对凋落叶的分解速率均有极显著影响(P<0.001),以UV-B辐射的影响更强烈;自然和UV-B辐射滤减环境下凋落叶的分解速率均与C∶N呈显著负相关(P<0.05)。     

Effects of enhanced ultraviolet-B radiation on water use efficiency, stomatal conductance, leaf nitrogen content and morphological characteristics of Spiraea pubescens in a warm-temperate deciduous broad-leaved forest

Spiraea pubescens, a common shrub in the warm-temperate deciduous forest zone which is distributed in the Dongling Mountain area of Beijing, was exposed to ambient and enhanced ultraviolet-B (UV-B, 280–320 nm) radiation by artificially supplying a daily dose of 9.4 kJ/m² for three growing seasons, a level that simulated a 17% depletion in stratospheric ozone. The objective of this study was to explore the effects of long-term UV-B enhancement on stomatal conductance, leaf tissue δ ¹³C, leaf water content, and leaf area. Particular attention was paid to the effects of UV-B radiation on water use efficiency (WUE) and leaf total nitrogen content. Enhanced UV-B radiation significantly reduced leaf area (50.1%) but increased leaf total nitrogen content (102%). These changes were associated with a decrease in stomatal conductance (16.1%) and intercellular CO₂ concentration/ air CO₂ concentration (C _i /C _a) (4.0%), and an increase in leaf tissue δ ¹³C (20.5‰), leaf water content (3.1%), specific leaf weight (SLW) (5.2%) and WUE (4.1%). The effects of UV-B on the plant were greatly affected by the water content of the deep soil (30–40 cm). During the dry season, differences in the stomatal conductance, δ ¹³C, and WUE between the control and UV-B treated shrubs were very small; whereas, differences became much greater when soil water stress disappeared. Furthermore, the effects of UV-B became much less significant as the treatment period progressed over the three growing seasons. Correlation analysis showed that enhanced UV-B radiation decreased the strength of the correlation between soil water content and leaf water content, δ ¹³C, C _i/C _a, stomatal conductance, with the exception of WUE that had a significant correlation coefficient with soil water content. These results suggest that WUE would become more sensitive to soil water variation due to UV-B radiation. Based on this experiment, it was found that enhanced UV-B radiation had much more significant effects on morphological traits and growth of S. pubescens than hydro-physiological characteristics. __________ Translated from Journal of Plant Ecology, 2006, 30(1): 47–56 [译自: 植物生态学报]     

The effects of ultraviolet-B radiation on photosynthesis of different aged needles in field-grown loblolly pine

We examined the effect of supplemental UV-B radiation (290-320 nm) on photosynthetic characteristics of different aged needles of 3-year-old, field-grown loblolly pine (Pinus taeda L.). Needles in four age classes were examined: I, most recently fully expanded, year 3; II, first flush, year 3; III, final flush, year 2; and IV, oldest needles still present, year 2. Enhanced UV-B radiation caused a statistically significant decrease (6%) in the ratio of variable to maximum fluorescence (F(v)/F(m)) following dark adaptation only in needles from the youngest age class, suggesting transient damage to photosynthesis. However, no effects of enhanced UV-B radiation on other instantaneous measures of photosynthesis, including maximum photosynthesis, apparent quantum yield and dark respiration, were seen for needles of any age. Foliar nitrogen concentration was unaffected by UV-B treatment. However, the (13)C/(12)C carbon isotope ratios (delta(13)C-a time integrated measure of photosynthetic function) of needles in age classes II and IV were 3% (P < 0.01) and 2% (P < 0.05) more negative, respectively, in treated plants than in control plants. Exposure to enhanced UV-B radiation caused a 20% decrease in total biomass and a 4% (P < 0.05), 25% (P < 0.01), and 9% (P < 0.01) decrease in needle length of needles in age classes I, II, and IV, respectively. The observed decreases in delta(13)C, and F(v)/F(m) of the needles in the youngest needle age class suggest subtle damage to photosynthesis, although overall growth reductions were probably a result of decreased total leaf surface rather than decreased photosynthetic capacity. Needles of age class IV had lower light- and CO(2)-saturated maximum photosynthetic rates (39%), lower dark respiration (34%), lower light saturation points (37%), lower foliar nitrogen concentration (28%), and lower delta(13)C (14%) values than needles of age class I. Apparent quantum yield and F(v)/F(m) did not change with needle age. The observed changes in photosynthesis and foliage chemical composition with needle age are consistent with previous studies of coniferous trees and may represent adaptations of older needles to shaded conditions within the canopy.     

根际微生态调节对杨树根系活力及土壤有效P转化的效应

以盆栽毛白杨、北京杨为试验材料,采用均匀设计,将外生菌根真菌（美味牛肝菌、褐疣柄牛肝菌）、植物生长调节剂（NAA）和植物抗病诱导剂（水杨酸）以不同配比混合形成根际微生态调节物,并施于苗木根部,研究其对苗木生长、生物量、根系活力、土壤酸性磷酸酶活性及土壤有效P的影响效应。结果表明,根际微生态调节物改善了苗木根际微生态环境,使毛白杨、北京杨盆栽苗的苗高、地径、总干质量均有较大幅度的提高,分别比对照增加16.0%~35.0%,19.4%~38.9%,15.5%~86.4%和12.5%~26.2%,1.6%~20.3%,33.6%~72.7%,幼苗生长更为健壮和迅速;使毛白杨根系活力比对照提高6.71%~33.64%,北京杨根系活力比对照提高1.49%~49.46%,根系活力与苗木的生长、生物量有较大相关性;使毛白杨和北京杨根际土壤酸性磷酸酶活性增强,分别增加20.91%~36.35%和13.39%~54.98%,对根际区域的土壤有效P具有明显的富集效应,富集率分别为7.49%~25.67%和17.85%~53.50%。     

芽变毛白杨及其亲缘种扦插生根相关内源酶活性特征分析

毛白杨为扦插难生根树种，而芽变毛白杨较易生根。芽变毛白杨插条内POD活性比毛白杨低，在生根过程中与另一亲缘种大官杨相比，POD活性变化趋势相反；IAAO活性与毛白杨变化趋势相反，与大官杨变化趋势基本相同。在不定根出现时期，芽变毛白杨插条内的POD和IAAO活性均为最高。芽变毛白杨组培苗生根过程中POD和IAAO活性变化趋势与田间苗类似。     

美洲黑杨与不同种源青杨杂种苗叶片和生长性状多水平变异研究

利用美洲黑杨50号为母本和青杨5个种源(各10个单株)为父本杂交,获得杂种F1代无性系,对此多水平杂交育种体系叶片和生长遗传变异进行了研究.结果表明,父本青杨种源间及种源内单株间均达到极显著差异,F1代无性系的种源间、种源内家系间和家系内无性系间存在不同差异.杂种F1代无性系扦插苗父本种源不同的杂交组合间和组合内家系间成活率差异不显著,1、2、3年生苗的生长性状在不同层次变异水平上差异显著或极显著,表明父本青杨种源间和种源内变异对F1代生长有显著影响,F1代无性系存在丰富的遗传变异,具有选择潜力.杂种F1代叶片形态与苗期生长性状间未发现有较大相关性.