共查询到20条相似文献，搜索用时 312 毫秒
1.
From January 1999 to May 2001, we investigated seasonal variations in the photosynthetic capacity of Taiwan spruce (Picea morrisonicola Hay.) growing in the subalpine region of subtropical Taiwan (23 degrees 29' N, 120 degrees 53' E, 2600 m a.s.l.). Photosynthetic capacity (near light-saturated net photosynthetic rate, Pnsat, chlorophyll fluorescence (Fv/Fm) and soluble protein concentration of needles all increased from mid or late spring to early winter. Even when minimum air temperature of the measuring day dropped to near 0 degrees C, Pnsat remained at about 20% of the highest value observed in winter. There was a curvilinear relationship between Fv/Fm and the minimum or mean air temperature of the measuring day. The increase in Fv/Fm with temperature was slowed when the daily mean air temperature was above 7 degrees C, or the minimum air temperature was above 3 degrees C; however, when air temperatures dropped below these values, Fv/Fm varied sharply. Seasonal variations in Pnsat paralleled those in Fv/Fm and needle soluble protein concentration. In early or mid spring when air temperature and Fv/Fm increased, Pnsat and soluble protein concentration remained low. Multiple regression analysis showed that seasonal variations in Pnsat were affected by Fv/Fm, air temperature and needle soluble protein concentration, and the multiple regression equation could be used to estimate Pnsat in different seasons. We conclude that the decrease in photosynthetic capacity of Taiwan spruce in winter and its subsequent recovery in spring were mainly caused by photoinhibition and its reversal, and changes in needle soluble protein concentration. Another possible explanation for the delayed recovery of photosynthetic capacity in spring may be associated with the slow increase in needle soluble protein concentration. 相似文献
2.
以加勒比松(Pinus caribaea)16个种源、湿地松(P.elliottii)4个种源2.5 a生营养袋苗木为材料,定期开展生长调查,于2016年7—8月、2017年2月开展叶绿素荧光参数的测定,分析加勒比松、湿地松针叶叶绿素荧光参数对树种、种源、不同测量时间的响应.结果表明,不同种源加勒比松/湿地松的株高、地径生长均存在显著差异(P<0.01);测量时间与树种对最大PSⅡ的光能转换效率(Fv/Fm)有显著影响(P<0.01),二者互作效应不显著,与7、8月相比,测量值均在第2年2月显著提高;两个树种的实际量子产量(ΦPSⅡ)、光化学淬灭(qP)与表观量子传递速率(ETR)对测量时间的响应模式相反;加勒比松与湿地松叶绿素荧光参数受种源影响不显著;相关性分析表明,加勒比松与湿地松的株高和地径生长与2月Fv/Fm、PSⅡ有效光化学效率(Fv′/Fm′)测量值呈一定的负相关关系;高光强抑制了湿地松、加勒比松的叶绿素荧光参数,但抑制效果与生长无明显相关关系;低温造成的胁迫主要抑制了加勒比松的光化学反应,并与其生长表现有一定的负相关关系.可考虑将2月份测量的叶绿素荧光参数作为加勒比松耐寒个体的筛选指标. 相似文献
3.
Sveshnikov D Ensminger I Ivanov AG Campbell D Lloyd J Funk C Hüner NP Oquist G 《Tree physiology》2006,26(3):325-336
We studied the influence of two irradiances on cold acclimation and recovery of photosynthesis in Scots pine (Pinus sylvestris L.) seedlings to assess mechanisms for quenching the excess energy captured by the photosynthetic apparatus. A shift in temperature from 20 to 5 degrees C caused a greater decrease in photosynthetic activity, measured by chlorophyll fluorescence and oxygen evolution, in plants exposed to moderate light (350 micromol m(-2) s(-1)) than in shaded plants (50 micromol m(-2) s(-1)). In response to the temperature shift, maximal photochemical efficiency of photosystem II (PSII), measured as the ratio of variable to maximal chlorophyll fluorescence (Fv/Fm) of dark-adapted samples, decreased to 70% in exposed seedlings, whereas shaded seedlings maintained Fv/Fm close to initial values. After a further temperature decrease to -5 degrees C, only 8% of initial Fv/Fm remained in exposed plants, whereas shaded plants retained 40% of initial Fv/Fm. Seven days after transfer from -5 to 20 degrees C, recovery of photochemical efficiency was more complete in the shaded plants than in the exposed plants (87 and 65% of the initial Fv/Fm value, respectively). In response to cold stress, the estimated functional absorption cross section per remaining PSII reaction center increased at both irradiances, but the increase was more pronounced in exposed seedlings. Estimates of energy partitioning in the needles showed a much higher dissipative component in the exposed seedlings at low temperatures, pointing to stronger development of non-photochemical quenching at moderate irradiances. The de-epoxidation state of the xanthophyll cycle pigments increased in exposed seedlings at 5 degrees C, contributing to the quenching capacity, whereas significant de-epoxidation in the shaded plants was observed only when temperatures decreased to -5 degrees C. Thermoluminescence (TL) measurements of PSII revealed that charge recombinations between the second oxidation state of Mn-cluster S2 and the semireduced secondary electron acceptor quinone Q(B)- (S2Q(B)-) were shifted to lower temperatures in cold-acclimated seedlings compared with control seedlings and this effect depended on irradiance. Concomitant with this, cold-acclimated seedlings demonstrated a significant shift in the S2 recombination with primary acceptor Q(A)- (S2Q(A)-) characteristic TL emission peak to higher temperatures, thus narrowing the redox potential gap between S2Q(B)- and S2Q(A)-, which might result in increased probability for non-radiative radical pair recombination between the PSII reaction center chlorophyll a (P680+) and Q(A)- (P680+)Q(A)-) (reaction center quenching) in cold-acclimated seedlings. In Scots pine seedlings, mechanisms of quenching excess light energy in winter therefore involve light-dependent regulation of reaction center content and both reaction center-based and antenna-based quenching of excess light energy, enabling them to withstand high excitation pressure under northern winter conditions. 相似文献
4.
We studied morphological and physiological leaf and whole-plant features of seedlings of six late-successional woody species common in the Xishuangbanna lowland rain forest in southwest China. Study species differed in adult stature and shade tolerance and included the shrubs Lasianthus attenuatus Jack and Lasianthus hookeri C.B. Clarke ex Hook. f.; the sub-canopy species Barringtonia macrostachya (Jack) Kurz and Linociera insignis C.B. Clarke; the canopy tree Pometia tomentosa (Blume) Teijsm. & Binn.; and the emergent species Shorea chinensis (Wang Hsie) H. Zhu. After 1 year of growth in low light (4.5% full sun), seedlings were transferred to high light (24.5% full sun) to investigate acclimation responses of existing leaves to forest gap opening and to determine whether seedling capacity for acclimation is a limiting factor in its natural regeneration. Leaves of the shrub species are shade-adapted, as indicated by their low photosynthetic capacity, efficiency in using sunflecks, low stomatal density, low Chl a/b ratio and high spongy/palisade mesophyll ratio. The shrub species utilized sunflecks efficiently because they had a short photosynthetic induction time and low induction loss. In all species, transfer of seedlings to high light resulted in a substantial initial reduction in the dark-adapted quantum yield of photosystem II (variable chlorophyll fluorescence/maximum chlorophyll fluorescence; Fv/Fm) at midday. Predawn Fv/Fm of the taller species did not change greatly, but predawn Fv/Fm of the shrub species decreased significantly without complete recovery within 25 days of transfer to high light, indicating chronic photoinhibition and damage to the previously shade-adapted leaves. Maximum net photosynthetic rate and dark respiration of the four taller species increased considerably after transfer to high light, but not in the shrub species. Similar trends were observed for the number of newly formed leaves and relative height growth rate. We conclude that the shrubs L. hookeri and L. attenuatus have limited potential for developmental and physiological acclimation to high light, which explains their absence from forest gaps. Compared with the shrub species, the taller tree species, which are more likely to experience high light during their life span, showed a greater potential for light acclimation. Physiological differences among the four tree species were not consistent with differences in adult stature. 相似文献
5.
Effects of chilling-dependent photoinhibition on gas exchange, chlorophyll fluorescence, growth and nutrition of Eucalyptus nitens (Deane and Maiden) Maiden seedlings were assessed for 70 weeks after transplanting 9-month-old seedlings in early winter. One month before transplanting, the seedlings were assigned to fertilized or nutrient-deprived treatments. Immediately after transplanting, half the seedlings in each nutrient treatment were placed in shadecloth tree shelters. The experimental site was at an altitude of 700 m, which is considered marginal for the establishment of E. nitens plantations in Tasmania because of low mean annual minimum temperatures. Overnight frosts followed by sunny morning conditions in the first 20 weeks after transplanting (early June to early October) caused severe photoinhibition. Predawn maximal photochemical efficiency (Fv/Fm) and maximum net photosynthesis (Amax) were depressed in nutrient-deprived seedlings compared with fertilized seedlings, although shading partially alleviated this difference. Neither Fv/Fm nor Amax recovered to values observed before transplanting until > 20 weeks after transplanting. During this period, non-photochemical quenching (NPQ) was high in seedlings in all treatments, although NPQ was lower in shaded, fertilized seedlings than in seedlings in the other treatments. Total foliar nitrogen (N) concentration increased up to 42 weeks after transplanting in the nutrient-deprived seedlings in parallel with increasing relative growth rate (RGR). Fractionation of N- and phosphorus (P)-containing compounds indicated that differences in protein N accounted for the treatment differences in total seedling N. Nucleic acid P increased and inorganic P decreased during growth periods, although total seedling P remained constant. Among treated seedlings, height growth was greatest in shaded seedlings: this was probably a result of apical dominance effects because RGR was higher in unshaded seedlings than in shaded seedlings. Thus, the shade treatment alleviated chilling-dependent photoinhibition and maximized growth during winter, but limited growth during warmer periods and therefore overall growth. 相似文献
6.
Photoinhibition of photosynthesis and photosynthetic recovery were studied in detached needles of cypress (Cupressus sempervirens L.) Clones 52 and 30 under controlled conditions of high irradiation (about 1900 micromol m(-2) s(-1) for 60 min; HL treatment), followed by 60 min in darkness. The degree of photoinhibition was determined based on the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm), which is a measure of the potential efficiency of photosystem II (PSII), and on electron transport measurements. The Fv/Fm ratio declined in needles of both clones in response to the HL treatment. Minimal fluorescence (Fo) increased in HL-treated needles of both clones. The HL treatment decreased rates of whole-chain and PSII activity of isolated thylakoids more in Clone 52 than in Clone 30. In needles of both clones, PSI activity was less sensitive to photoinhibition than PSII activity. In the subsequent 60-min dark incubation, fast recovery was observed in needles of both clones, with PSII efficiencies reaching similar values to those in non-photoinhibited needles. The artificial exogenous electron donors diphenyl carbazide (DPC), hydroxylamine (NH2OH) and manganese chloride (MnCl2) failed to restore the HL-induced loss of PSII activity in needles of Clone 30, whereas DPC and NH2OH significantly restored PSII activity in photoinhibited needles of Clone 52. Quantification of the PSII reaction center protein D1 and the 33-kDa protein of the water-splitting complex following HL treatment of needles revealed pronounced differences between Clone 52 and Clone 30. The large decrease in PSII activity in HL-treated needles was caused by the marked loss of D1 protein and 33-kDa protein in Clone 30 and Clone 52, respectively. 相似文献
7.
We examined the principal differences in photosynthetic characteristics between sun and shade foliage and determined the relative importance of biochemical and stomatal limitations during photosynthetic induction. Temperate-zone broadleaf and conifer tree species, ranging widely in shade tolerance, were investigated from one locality in the Czech Republic. The study species included strongly shade-tolerant Abies alba Mill. and Tilia cordata Mill., less shade-tolerant Fagus sylvatica L. and Acer pseudoplatanus L. and sun-demanding Picea abies (L.) Karst. In the fully activated photosynthetic state, sun foliage of all species had significantly higher maximum CO(2) assimilation rates, maximum stomatal conductance and maximum rates of carboxylation than shade foliage. Compared with shade leaves, sun leaves had significantly higher nocturnal stomatal conductances. In all species, shade foliage tended to have higher induction states 60 s after leaf illumination than sun foliage. Sun and shade foliage did not differ in the rate of disappearance of the transient biochemical limitation during the induction phase. Longer time periods were required to reach 90% photosynthetic induction and 90% stomatal induction in sun foliage than in shade foliage of the less shade-tolerant F. sylvatica and A. pseudoplatanus and in sun-demanding P. abies; however, in sun foliage of the strongly shade-tolerant species T. cordata and A. alba, the time needed for photosynthetic induction was similar to, or less than, that for shade foliage. Shade but not sun needles of P. abies and A. alba had significantly slower induction kinetics than the broadleaf tree species. Among species, the sun-demanding P. abies exhibited the shortest stomatal induction times in both sun and shade leaves. Independently of shade tolerance ranking, the transient stomatal and total limitations that characterize photosynthetic induction were relieved significantly earlier in shade foliage than in sun foliage. Sun foliage generally exhibited a hyperbolic photosynthetic induction response, whereas a sigmoidal induction response was more frequent in shade foliage. The different relative proportions of transient biochemical and stomatal limitations during photosynthetic induction in sun and shade foliage indicate an essential role of stomata in photosynthetic limitation during induction, mainly in shade foliage, with a consequent influence on the shape of the photosynthetic induction curve. 相似文献
8.
以白杨派和黑杨派杨树的盆栽苗为试材,分析了不同干旱胁迫程度对5个杨树的气体交换参数与荧光参数(Fv/Fm、Fmv/Fms)的影响,并对不同树种的耐旱性进行了综合评价。结果表明:①5种杨树净光合速率与蒸腾速率均随苗木叶水势的下降而呈明显下降趋势;在水分胁迫初期,欧洲黑杨和银白杨的净光合速率呈现明显的上升趋势。②在中度干旱胁迫前,5个供试杨树的水分利用效率大部分随叶水势的下降有增大现象。③不同树种的Fv/Fm随叶水势降低总体上呈逐渐下降趋势。④与Fv/Fm相比,Fmv/Fms能更直接地反映光合机构的实际光能捕获能力。⑤当苗木叶水势为-1.5 MPa时,5个树种耐旱性的综合评价结果为:转Bt基因欧洲黑杨>欧洲黑杨>银白杨>银灰杨为欧洲山杨,综合指数评价结果与采用单一指标中的水分利用效率完全一致,与净光合速率相近;水分利用效率证明是一种较为可靠的树种耐旱性评价指标。 相似文献
9.
The role of morphological versus physiological foliar plasticity in the capacity for, and mechanisms of, photosynthetic acclimation was assessed in Picea abies (L.) Karst. and Abies alba Mill. saplings in a forest gap-understory light gradient (relative irradiance, RI, ranging from 0.02 to 0.32). The species investigated showed a similar foliar morphological plasticity along the light gradient, at both the needle level (through alteration in leaf dry mass per area) and the shoot level (through alteration in the silhouette area ratio, e.g., shoot silhouette to projected needle area ratio). In both species chlorophyll (Chl) concentration on a mass basis decreased at increasing RI, but was independent of RI when expressed on an area basis. In contrast, leaf N concentration on a mass basis was independent of RI, but was positively influenced by RI when expressed on an area basis. The parameters describing photosynthetic performance at low light (dark respiration rate, apparent quantum yield and light compensation point) suggest that Abies alba was better suited to maintain a positive carbon balance in shaded conditions. By contrast, parameters describing biochemical capacity at high light (maximum electron transport rate, Jmax and maximum ribulose-1,5-biphosphate carboxylation capacity, Vcmax) indicate that only Picea abies was capable of acclimating physiologically to high photosynthetic photon flux densities (PPFDs) by increasing nitrogen partitioning to Rubisco and Vcmax/mass by increasing RI. These results support the hypothesis that interspecific differences in nitrogen partitioning within the photosynthetic apparatus may provide a mechanistic basis for species separation along a light gradient. The differences in photosynthetic plasticity observed are likely to influence regeneration patterns and habitat breadth of the species investigated. The limited ability of Abies alba saplings to exploit high-light conditions may be a competitive disadvantage in large canopy gaps and thus limit recruitment of this species to small gaps. 相似文献
10.
The photosynthetic characteristics of current-year stems of six deciduous tree species, two evergreen tree species and ginkgo (Ginkgo biloba L.) were compared. Gas exchange, chlorophyll concentration, nitrogen concentration and maximum quantum yield of PSII were measured in stems in summer and winter. A light-induced decrease in stem CO(2) efflux was observed in all species. The apparent gross photosynthetic rate in saturating light ranged from 0.72 micromol m(-2 )s(-1) (ginkgo, in winter) to 3.73 micromol m(-2) s(-1) (Alnus glutinosa (L.) Gaertn., in summer). Despite this variability, a unique correlation (slope = 0.75), based on our results and those reported in the literature, was found between gross photosynthetic rate and dark respiration rate. Mass-based gross photosynthetic rate decreased with stem mass per area and correlated to chlorophyll concentration and nitrogen concentration, both in summer and winter. The radial distribution of stem chlorophyll differed among species, but all species except ginkgo had chlorophyll as deep as the pith. In summer, the maximum quantum yield of stem PSII (estimated from the ratio of variable to maximal fluorescence; F (v)/F (m)) of all species was near the optimal value found for leaves. By contrast, the values were highly variable in winter, suggesting large differences in sensitivity to low-temperature photoinhibition. The winter values of Fv/Fm were only 31-60% of summer values for the deciduous species, whereas the evergreen conifer species maintained high F (v)/F (m) in winter. The results highlight the interspecific variability of gross photosynthesis in the stem and its correlation with structural traits like those found for leaves. The structural correlations suggest that the selection of photosynthetic traits has operated under similar constraints in stems and leaves. 相似文献
11.
以马尾松(Pinus massoniana)和杉木(Cunninghamia lanceolata)为试验材料,通过盆栽的方法,研究了重度酸雨处理、中度酸雨处理和酸雨对照处理对这两种针叶植物叶片叶绿素相对含量、气体交换参数以及叶绿素荧光特性等的影响.结果表明:在pH4.0时,酸雨胁迫对马尾松和杉木幼苗的地径生长有一定的促进;在不同酸雨处理下,马尾松幼苗的最大净光合速率从大到小依次是pH5.6>pH4.0>pH2.5;杉木幼苗的最大净光合速率从大到小依次是pH2.5>pH4.0>pH5.6,说明这2种植物幼苗的光合能力受到影响;Fv/Fm和Fv/Fo随着酸雨酸度的增加而减小,变化趋势是pH5.6>pH4.0>pH2.5,说明在pH 2.5的酸雨胁迫下,两种针叶植物幼苗叶片受到胁迫,叶绿素分子捕获激发能的效率和PSⅡ潜在活性有所降低. 相似文献
12.
Photoinhibition was examined in four co-occurring Mediterranean evergreen tree species during two consecutive winters. In response to low temperatures and saturating light, Juniperus phoenicea L., Pinus halepensis Mill., Quercus coccifera L. and Q. ilex ssp. ballota (Desf.) Samp. exhibited marked chronic photoinhibition, indicated by low predawn maximal photochemical efficiency of photosystem II (PSII) (Fv/Fm). Low Fv/Fm values were correlated with high concentrations of xanthophyll cycle components (VAZ) and with the maintenance of high concentrations of zeaxanthin overnight (DPSpd). In all species, however, chronic photoinhibition was enhanced as the winter progressed in the absence of changes in DPSpd, suggesting cumulative damage toward the end of winter. Photoinhibition differed among species: P. halepensis always displayed significantly higher Fv/Fm values; and Q. coccifera had the lowest Fv/Fm values, showing a high sensitivity to the combination of high light and low temperatures. Differences among species were not fully explained by differences in the xanthophyll pool or its de-epoxidation state. Chronic photoinhibition overlapped with a dynamic photoinhibition as shown by the low values of photochemical efficiency of the open reaction centers of PSII at midday. Winter photoprotective strategies differed among species and may involve photoprotective mechanisms in addition to those associated with xanthophylls. The observed species-specific differences matched results obtained for the same species in summer; however, comparison of the two seasons suggests that the higher VAZ concentration observed in winter has an additional structural photoprotective role. 相似文献
13.
Leaves developing in different irradiances undergo structural and functional acclimation, although the extent of trait plasticity is species specific. We tested the hypothesis that irradiance-induced plasticity of photosynthetic and anatomical traits is lower in highly shade-tolerant species than in moderately shade-tolerant species. Seedlings of two evergreen conifers, shade-tolerant Abies alba Mill. and moderately shade-tolerant Picea abies Karst., and two deciduous angiosperm species, highly shade-tolerant Fagus sylvatica L. and moderately shade-tolerant Acer pseudoplatanus L., were grown in deep shade (LL, 5% of full irradiance) or in full solar irradiance (HL) during 2003 and 2004. Steady state responses of quantum yield of PSII (Phi(PSII)), apparent electron transport rate (ETR), nonphotochemical quenching (NPQ) and photochemical quenching (qP) were generally modified by the light environment, with slower declines in Phi(PSII) and qP and greater maximal ETR and NPQ values in HL plants in at least one season; however, no link between quantitative measures of plasticity of these traits and shade tolerance was found. Plasticity of nine anatomical traits (including palisade cell length, which was reduced in LL) showed no relationship with shade tolerance, but was less in conifers than in deciduous trees, suggesting that leaf life span may be a significant correlate of plasticity. When LL-acclimated plants were exposed to HL conditions, the degree and duration of photoinhibition (measured as a decline in maximum quantum yield) was greatest in F. sylvatica, much lower in P. abies and A. alba, and lowest in A. pseudoplatanus. Thus, as with the other traits studied, vulnerability to photoinhibition showed no relationship with shade tolerance. 相似文献
14.
水分和热胁迫处理对三个针叶树种苗木叶绿素荧光的影响 总被引：7，自引：0，他引：7
本文测定了三个周期水分和热胁迫处理对杉木、马尾松和北美乔柏苗木叶绿素荧光的影响。结果表明：三个树种的可变荧光与最大荧光之比值(Fv／Fm)对水分胁迫的反应不同。水分胁迫处理后北美乔柏的(Fv／Fm)值大大降低，而杉木的(Fv／Fm)值只有轻微下降，马尾松的(Fv／Fm)值则没有显著变化。实验结果还表明：热胁迫处理对三个树种的(Fv，Fm)值都有显著影响。就三个水分和热胁迫周期而言，研究发现：在每个水分和热胁迫周期结束时测定的杉木和马尾松(Fv／Fm)值没有显著差异。但随着胁迫时间的延长，北美乔柏的(Fv／Fm)值显著下降。图4表4参20。 相似文献
15.
以黑果枸杞‘黑杞1号’和宁夏枸杞‘宁杞7号’的1年生幼苗为试材,用NaCl和Na_2CO_3溶液进行处理,研究盐胁迫条件下,枸杞幼苗生长、光合作用和叶绿素荧光参数的变化。结果表明,2种枸杞在NaCl和Na_2CO_3胁迫下,幼苗生长、光合作用和叶绿素荧光参数的变化趋势基本相同,但不同盐不同品种间幼苗生长、光合作用和叶绿素荧光参数值存在差异。生长特性方面,盐胁迫主要影响株高和基径;在光合和叶绿素荧光特性方面,盐胁迫主要影响的参数有P_n、G_s、C_i、T_r、Ф_(PSⅡ)、F_o、F_m、F_v/F_m、C_(qP)、C_(qN)、叶绿素a含量、叶绿素b含量、总叶绿素含量,其中,P_n、G_s、C_i、F_o、C_(qP)、Ф_(PSⅡ)和总叶绿素含量与对照相比差异显著,T_r、F_m、F_v/F_m、C_(qN)、叶绿素a含量和叶绿素b含量与对照相比无显著差异。NaCl胁迫后,‘黑杞1号’和‘宁杞7号’幼苗的生长量、光合速率分别在1.3 mol·L~(-1)和1.2 mol·L~(-1)时达到最高值,在1.5 mol·L~(-1)时,达到耐盐极限值;Na_2CO_3胁迫后,‘黑杞1号’和‘宁杞7号’幼苗的生长量、光合速率在0.1 mol·L~(-1)时达到最高值,分别在0.4 mol·L~(-1)和0.5 mol·L~(-1)达到耐盐极限值。所以,‘黑杞1号’耐盐能力强于‘宁杞7号’,且Na_2CO_3对枸杞幼苗影响显著大于NaCl。 相似文献
16.
In the context of climate change, an increased frequency of drought stresses might occur at a regional scale in boreal forests. To assess photosynthetic responses to drought treatment, seedlings of 12 open-pollinated families of white spruce (Picea glauca (Moench) Voss) differing in their growth performance were grown in a controlled environment. Gas exchange and chlorophyll fluorescence parameters as well as shoot xylem water potential (WP) were measured for 21 successive days after watering was stopped. Net photosynthesis decreased as stomatal conductance decreased. Net photosynthesis was not affected by drought until WP reached –2.0 MPa when stomata were closed. Initial fluorescence (F and basic fluorescence after induction (F00) were not affected by drought. A progressive decrease in maximal (Fm) and variable fluorescences (Fv), maximum photosystem II (PS II) efficiency (Fv = Fm), effective quantum yield of PS II (FII), photochemical efficiency of open PS II (Fp), and photochemical quenching (qP) was observed at WP < - 1.0 MPa, whereas non-photochemical quenching (qN) remained high throughout the drought treatment. White spruce families with inferior growth performance showed higher values of Fm, Fv, Fv = Fm, Fp, and qN at WP< - 2.0MPa. The results indicated that chlorophyll fluorescence variables can be used as drought markers in relation to present or predicted climate conditions. These could be used for selecting planting stock adapted to drought periods or dry environments. These markers showed that slow-growing genotypes are better adapted to drought conditions than intermediate or fast-growing genotypes in present and predicted drought conditions. 相似文献
17.
18.
Chrysomyxa rhododendri (DC.) De Bary is a needle rust with a host shift between Rhododendron sp. and Norway spruce (Picea abies (L.) Karst.), penetrating only the new developing flushes of the conifer. Because little is known about its effects on trees, we investigated several parameters related to photosynthesis in artificially infected 3-year-old Norway spruce seedlings. The potential efficiency of photosystem II (PSII; derived from chlorophyll fluorescence measurements) was reduced in infected current-year needles as soon as disease symptoms were visible, about three weeks after inoculation. Two weeks later, photosynthetic O(2) evolution (P(max)) of infected needles was less than 20% of control needles, whereas respiratory O(2) uptake (R(D)) was about three times higher than that of control needles. Nonstructural carbohydrate concentrations were about 60% of control values in all parts of the shoots of infected trees. Photosynthetic inhibition was associated with marked decreases in chlorophyll concentration and chlorophyll a/b ratio but only a small reduction in carotenoid concentration. In infected trees, P(max) of noninfected 1-year-old and 2-year-old needles was 50 and 80% higher than in the corresponding age class of needles of control trees. Estimation of potential daily net dry mass production, based on P(max), R(D), specific leaf area, carbon content and needle biomass, indicated that seedlings infected once were able to produce 60%, and those infected twice only 25%, of the dry mass of controls. We conclude that afforestation and regeneration of Norway spruce is seriously impaired in regions where seedlings are frequently attacked by Chrysomyxa. 相似文献
19.