盐胁迫下1年生麻栎实生苗的生理变化

采用室内盆栽法对1年生麻栎实生苗进行了盐(Na Cl)胁迫试验,结果显示,土壤含盐量为0.4%和0.5%时,苗木叶片边缘会出现明显的失绿现象。高含量的盐处理会明显抑制麻栎新梢生长。土壤含盐量高于0.3%时,苗木叶片的含水量、叶绿素含量和光合速率均显著下降,而相对电导率显著升高。土壤含盐量较高时,苗木嫩叶中的N含量有所下降。苗木细根中的K含量会随着土壤含盐量的提高而降低,叶片中的K含量却呈相反趋势。当土壤含盐量低于0.3%时,苗木叶片中的Na含量处于较低水平,但高于0.4%时,叶片中的Na含量会显著升高;细根中的Na含量随着土壤含盐量的升高而升高。综合分析认为,土壤含盐量低于0.2%时,麻栎苗木能够正常生长;土壤含盐量高于0.3%时,麻栎苗木的生理会受到明显影响。     

干旱胁迫对麻栎无性系蒸腾作用的影响

以13个3年生麻栎无性系为研究对象,采用盆栽试验方法,研究了在持续干旱胁迫条件下的麻栎无性系土壤水势、叶片水势光合速率和蒸腾速率变化规律及其关系。结果表明,随着干旱胁迫的加剧,13个麻栎无性系土壤水势呈现出不断下降的变化趋势,叶片水势的变化无一致规律,光合速率则先下降而后上升,蒸腾速率的变化规律不尽相同。在13个麻栎无性系中,2、4、5、7、9和16号无性系的蒸腾速率、叶片水势和光合速率具有相同规律,随着干旱胁迫的加剧先下降而后上升,具有较强的适应干旱逆境的能力。对不同干旱条件下无性系的蒸腾速率、土壤水势、叶片水势和光合速率的相关性分析发现,干旱胁迫7天时,蒸腾速率和光合速率达极显著正相关;干旱胁迫12天时,蒸腾速率和土壤水势间呈极显著负相关,光合速率与土壤水势呈显著负相关;干旱胁迫17天时,蒸腾速率与光合速率呈显著正相关。     

淹水胁迫对麻栎苗木生长和生理的影响

采用室内盆栽控制试验,研究了麻栎苗木在不同淹水处理下的生长和生理变化。结果表明,经过1个月的淹水试验,麻栎苗木未出现死亡现象,说明麻栎具有较强的耐水能力;但是不同处理之间的苗木生长和生理性状存在一定差异,主要是淹水处理后的麻栎苗木新梢生长均明显小于对照处理。经淹水处理后苗木叶片含水量、叶绿素含量以及光合速率均明显低于对照处理,但是叶片相对电导率呈相反趋势。淹水后麻栎苗木叶片中的N、P、K含量均比对照低。淹水处理会导致叶片Na含量增加,且随着淹水强度的增强而增加。     

短期干旱和复水对麻栎幼苗光合及叶绿素荧光的影响

麻栎是鲁中山区森林植被恢复的重要阔叶树种之一,本文以1年生麻标幼苗为试验对象,研究短期干旱和复水对其光合及叶绿素荧光等生理生态特征的影响。结果表明：在干旱胁迫初期,干旱组的各项指标均优于对照组,说明过高的土壤含水量并不利于麻栎幼苗的生长;随着土壤干旱程度的进一步加剧,幼苗的气孔导度减少,导致光合和蒸腾作用的下降,水分利用效率升高;胁迫末期各项光合指标均降到最低。从叶绿素荧光参数可以看出,干旱胁迫并未使幼苗的光合机构发生伤害,幼苗在适宜的水分条件时产生光合能力上调,当水分匮缺时,以叶黄素循环为主的非光化学淬灭耗散掉过剩的光能达到保护光合机构的目的。复水后麻栎幼苗的各项生理生态指标恢复正常,但气孔导度的增大存在一定的滞后效应,导致了水分利用效率的反冲,同时叶黄素库仍然维持较高水平,麻栎幼苗通过物理和化学的双重保护来抵御干旱胁迫和进行胁迫后的恢复。     

干旱胁迫对樟树幼苗光合特性和水分利用的影响

使用LI-6400XT便携式光合作用测量系统对不同水分条件下的樟树幼苗进行光合指标的测定,探究樟树幼苗在干旱胁迫下的自我调节与适应性,为苗期栽培提供参考依据。结果显示:1)在轻度胁迫(LS)、中度胁迫(MS)、重度胁迫(SS)的条件下,樟树幼苗的叶绿素a、叶绿素b、总叶绿素含量与叶绿素a/b均存在先上升后下降的趋势,胁迫结束时均存在显著差异(P <0.05),且重度胁迫(SS)时叶绿素含量下降程度较大,叶绿素a下降幅度略高于叶绿素b,导致叶绿素a/b的比值下降;2)净光合速率(P_n)、气孔导度(G_S)、蒸腾速率(T_r)、胞间CO_2浓度(C_i)在干旱条件下持续下降,在重度干旱(SS)条件下下降幅度最高,各组间差异性显著(P <0.05);3)轻度干旱(LS)与中度干旱(MS)下胁迫结束时水分利用效率(R_WUE)高于对照组,重度干旱(SS)则略低于对照组;4)在干旱胁迫条件下,一年生香樟幼苗可通过调节叶绿素含量与水分利用情况来适应干旱逆境。     

Growth and physiological responses of Quercus brantii seedlings inoculated with Biscogniauxia mediterranea and Obolarina persica under drought stress

Charcoal canker of oak is a common disease in the western regions of Iran, which has widely spread due to climate change and increasing drought in recent years. Biscogniauxia mediterranea and Obolarina persica are known as two agents of oak charcoal canker in Zagros forests causing the dieback of oak trees. The effects of charcoal disease agent pathogens on the growth and physiological response of two‐year‐old seedlings of Quercus brantii were evaluated under drought stress in greenhouse over a period of nine months. Survival was 21.7% lower in seedlings inoculated with B. mediterranea subjected to drought stress compared with control treatment. The length of lesions on stems was 68% more under charcoal pathogens in drought stressed compared with the length of lesions caused by charcoal pathogens only. On the other hand, stem lesion length caused by B. mediterranea was 25% greater than those caused by O. persica. Some morphophysiological characteristics were affected by charcoal pathogens alone and/or in combination with drought. Diameter, height and biomass decreased the most in seedlings inoculated with charcoal pathogens under drought stress. Pathogenic agents alone and in combination with drought stress reduced photosynthetic rates, stomatal conductance, transpiration, the maximum Rubisco activity (V_cmax), maximum photochemical efficiency of photosystem II (F_v/F_m) and xylem water potential. In general, drought increased the aggressiveness of fungus and intensification of their destructive effects in Quercus brantii. Moreover, there was no significant difference between the effect of B. mediterranea and O. persica on the morphophysiological parameters studied.     

Growth and nutrient use efficiency of water tupelo seedlings in flooded and well-drained soil

Growth characteristics and nutrient utilization rate of Nyssa aquatica L. seedlings grown in pots containing flooded or well-drained soil were compared in a greenhouse study. For most of the growing season, relative height and diameter growth rates, and biomass accumulation rates were greater for seedlings in flooded soil than for seedlings in well-drained soil. The concentration of Fe in the roots of seedlings in flooded soil was almost tenfold greater than that of seedlings in well-drained soil. However, flooding had no effect on foliar Fe concentrations. The flooding treatment resulted in decreased concentrations of N in all component parts and increased concentrations of P in the roots and stem, but it had no effect on foliar P concentrations. In response to flooding, foliar K concentrations decreased, whereas the concentration of K in the roots increased. Flooding had no effect on the K concentration of the stem. Seedlings in flooded soil produced more total biomass per milligram of nutrient absorbed than seedlings in well-drained soil, suggesting that N. aquatica seedlings are more efficient at producing biomass and height growth under hydric conditions than under mesic conditions.     

干旱胁迫下马尾松苗木生理变化

对广东信宜、浙江江山、湖南汝城、重庆黔江和湖北大悟5个种源马尾松苗木进行不同程度的周期性干旱胁迫,分析干旱胁迫下马尾松苗木生理指标变化规律.结果表明:大多数种源马尾松苗木叶绿素含量和根系活力在中度或重度干旱胁迫下高于对照,丙二醛含量在中度或重度干旱胁迫下也低于对照,表现出积极的抗旱反应.     

麻栎不同播种量及施肥生理效应的研究

不同播种量及施肥对麻栎苗木生长均有一定影响,从本次试验结果来看,麻栎的适宜播种量为1800kg·hm-2和2250kg·hm-2;麻栎播种苗在不同生长阶段内,N、P含量的高低不仅与施肥量有关,而且与苗木所处物候期、对土壤养分的吸收和利用状况、苗木本身生长节律等密切相关;不同施肥区,麻栎苗木叶绿素含量在速生期时最高,到生长后期相对降低。     

Morphological and physiological acclimation of Quercus coccifera L. seedlings to water availability and growing medium

One of the main constraints of reforestation in the Mediterranean region is low summer water availability during the first years after out planting. Plant water availability depends on the precipitation regime, but also on the physical properties of the soil. Higher survival rates result when seedlings are soil acclimated. Our main goal was to describe the morpho-physiological responses of 6-, 10- and 18-month-old Quercus coccifera seedlings growing in a natural soil (terra rossa) or a standard nursery growing medium, and to assess in the nursery if seedlings growing in natural soil were more resistant to deficit irrigation. The high growth rate achieved after 10?C18 months by terra rossa-grown seedlings in contrast with those grown in the nursery substrate suggests that the former were acclimated to the soil. Higher photosynthetic rate (A), transpiration (E) and stomatal conductance (g_s) were observed in terra rossa seedlings, mainly during the first months. The higher carbon availability may account for the higher root nitrogen concentration in terra rossa-grown seedlings, which could favor their later field growth. Low-watered seedlings showed a certain degree of hardening, since after 18 months, they showed higher A, E, g_s and lower photoinhibition than well-watered seedlings, likely attributable to the sharp leaf-to-root biomass ratio reduction. Carbon isotope discrimination (??) values were similar to those of well-watered plants and indicated a non-stomatal component as the main factor controlling photosynthesis in these leaves. Eighteen-month-old low irrigated seedlings had the highest mortality. Overall, results suggest that nursery terra rossa-acclimated Q. coccifera seedlings with improved physiological status and hydraulic soil-root continuity would have a higher survival rate in the field.     

Leaf physiology and sugar concentrations of transplanted Quercus rubra seedlings in relation to nutrient and water availability

Newly planted seedlings incur transplant stress resulting from poor root-soil contact, which limits access to soil moisture and nutrients and reduces growth for one or more growing seasons. Controlled release fertilizer (CRF) applied at planting may reduce transplant stress by augmenting rhizosphere nutrient availability yet with potential risk of root system damage due to elevated fertilizer salt concentrations, which may be further exacerbated by drought. Under controlled conditions, we examined northern red oak (Quercus rubra L.) leaf physiological parameters and soluble sugar concentrations in response to varying nutrient levels (via CRF application) and moisture availability gradients ranging from drought to flooding. Net photosynthetic rates, transpiration rates, and chlorophyll fluorescence parameters responded positively to CRF application, and no interactions were observed between CRF and moisture availability; however, CRF did not increase soluble sugar concentrations. No effects of short-term drought were observed, but flooding exerted a rapid negative influence on net photosynthetic rates, transpiration rates, and chlorophyll fluorescence parameters; flooding also elevated soluble sugar concentrations, indicative of disrupted carbon partitioning and a much greater sensitivity to root-zone hypoxia than to drought in this species. Lack of interactions between CRF application and soil moisture availability indicates relatively similar responses of fertilized seedlings across moisture gradients.     

Arbuscular mycorrhizal fungi improve the growth and drought tolerance of Zenia insignis seedlings under drought stress

New Forests - Drought is one of the most critical limiting environmental factors for plant survival and restoration in areas of rocky desertification in southwestern China. Here, we aimed to...     

水分胁迫下实生桑苗光合特性的研究

以1 a生实生桑为试材,采用盆栽控水法,设置了4个土壤水分处理(土壤相对含水量分别为75%~80%、65%~70%、45%~50%和25%~30%),研究水分胁迫对光合作用的影响,意在为不同立地条件下栽培实生桑提供理论依据。结果表明,除土壤含水量为25%~30%处理外,净光合速率日变化均呈现"双峰"型,有明显"午休"现象;在土壤水分胁迫下,叶绿素含量(CHL)、净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)均随土壤含水量下降而下降,胞间CO2浓度(Ci)在土壤相对含水量45%~50%前后呈先下降后上升的趋势;光合参数间相关性随土壤相对含水量的下降而逐渐下降。     

Drought resistance and water use efficiency of conifer seedlings treated with paclobutrazol

Growth and drought resistance of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), lodgepole pine (Pinus contorta (Loud.)), and white spruce (Picea glauca (Moench) Voss) container seedlings, treated with paclobutrazol at different times and with concentrations up to 2.8 mM, were examined over their second growing season. In two experiments all three species were planted in sand beds in the open and subjected to different levels of moisture stress. Paclobutrazol drenches of 0.3 and 0.6 mM made twice in October, prior to planting the following March, reduced dry weight growth the least, or increased growth in lodgepole pine under dry conditions. Paclobutrazol generally decreased survival under drought stress, particularly if treatment was applied immediately before planting, rather than the previous October. In a third experiment paclobutrazol treated white spruce were grown, in 3.1 L capacity containers filled with peat and vermiculite, at different moisture supply levels and temperatures in growth chambers. Water use efficiency (WUE) was calculated from water use and increases in dry weight of these seedlings over 83 days. Paclobutrazol treatment increased WUE most strongly over the first 31 day measurement period, under all temperature and moisture conditions, but the effect was negligible during the last 24 days of the experiment, and height growth was reduced by treatment. Mineral nutrient concentrations were affected by paclobutrazol, and it was concluded that these and other responsed depended partly on seedling condition at the time of treatment.     

Canopy development and solar conversion efficiency in Acacia auriculiformis under drought stress

A glasshouse experiment was performed with Acacia auriculiformis seedlings to investigate the effects of decreased soil water potential on phyllode extension, abscission and solar conversion efficiency, e. Six-month-old seedlings were subjected for 39 days to one of four treatments: well watered (soil water potential maintained above -0.5 MPa), moderately drought stressed (soil water potential maintained above -1.5 MPa), severely drought stressed (soil water potential maintained above -2.5 MPa) and well watered but pruned to maintain a leaf area approximating that of the severely drought-stressed treatment. Aboveground biomass accumulation decreased by 21% below that of the well-watered controls in the moderately drought-stressed seedlings and by 47% in the severely drought-stressed seedlings as a result of both decreased interception of solar radiation and lower e. Differences in phyllode extension rate, rather than in phyllode abscission, were primarily responsible for the differences in interception of solar radiation among treatments. Decreases in phyllode extension rate and water use occurred simultaneously in response to decreasing soil water potential. Specific leaf area decreased and water use efficiency increased in response to drought stress.     

Effects of nutrition and soil water availability on water use in a Norway spruce stand

We investigated effects of nutrition and soil water availability on sap flux density, transpiration per unit leaf area (EL), and canopy stomatal conductance (GS) of Norway spruce (Picea abies L. (Karst.)) in northern Sweden during the 1996 growing season. Our objectives were to determine (1) if artificially imposed drought (65% rain diversion) reduces soil water sufficiently to cause physiological limitations to whole-tree and plot-scale water transport, and (2) whether increased capacity for water transport resulting from fertilization-induced increases in leaf (> 3-fold) and sapwood areas (> 2.3-fold) deplete soil water sufficiently to cause a negative feedback on GS and EL. We monitored soil water content (theta) and soil water potential (PsiS) in control (C), drought (D), fertilized (F) and irrigated + fertilized (IL) treatment plots, along with site meteorological conditions. Ten trees per plot were monitored for sap flow. Although there were significant treatment differences in mean daily EL (C > D > F; P < 0.01) and GS (C > D > F; P < 0.05), variation in absolute magnitudes was small. Therefore, transpiration differences on a unit ground area basis (EC) were nearly proportional to leaf area differences. Precipitation was well distributed throughout the study period and so PsiS remained high, except during short dry periods in Plot F when it declined rapidly. Thus, although soil water was not limiting to GS, EL or EC when precipitation was uniformly distributed throughout the growing season, we cannot conclude that water availability would not limit GS in fertilized stands if the seasonal distribution of precipitation were altered.     

干旱胁迫对降香黄檀幼苗生理特性及根系形态特征的影响

采用盆栽控制土壤水分法,研究了1年生降香黄檀幼苗在不同干旱梯度胁迫条件下相对电导率、游离脯氨酸含量、光合特性等生理指标以及根系形态参数的变化.结果表明:随着干旱胁迫的加强,降香黄檀幼苗叶片电导率和脯氨酸含量变化整体呈上升的趋势;净光合速率Pn、蒸腾速率Tr、气孔导度Gs均下降,胞间CO2浓度Ci先降后升;与正常供水(W1)相比,在轻度干旱胁迫(W2)条件下,降香黄檀叶片Pn的降低主要是由气孔限制引起的,而在中度干旱胁迫(W3)和重度干旱胁迫(W4)条件下则主要由非气孔因素引起的.在重度干旱胁迫下,降香黄檀总根长、总根尖数和平均根系直径均显著降低,说明降香黄檀幼苗的耐旱能力有限.     

干旱胁迫对红椿盆栽土壤含水率与植株伤害程度的影响

以2年生红椿盆栽幼苗为对象,开展干旱胁迫及复水试验,对各观测日的土壤含水率、叶片伤害指数及植株萎蔫度进行分析,结果表明:(1)各时间段受试盆栽土壤含水率及叶片伤害指数差异均呈极显著差异;(2)复水一定程度上改善了胁迫伤害;(3)土壤含水率与植株受伤害程度呈极显著的负相关关系。(4)要保证2年生红椿幼苗的正常生长,必须将土壤含水率保持在25%以上。     

Diversity of water use efficiency among Quercus robur genotypes: contribution of related leaf traits

? Previously, a large intra-specific diversity and a tight genetic control have been shown for Δ¹³C (carbon isotope discrimination) in a pedunculate oak (Quercus robur L.) family, which is an estimator for intrinsic water use efficiency (W _i), a complex trait defined as the ratio of net CO₂ assimilation rate (A) to stomatal conductance for water vapour (g _s ).

? In the present study, twelve genotypes with extreme phenotypic values of Δ¹³C were selected within this family to (i) asses the stability of genotype differences across contrasting environments and for different measures W _i; (ii) quantify the relationship between Δ¹³C and W_i within this family; (iii) identify which leaf traits drive the diversity in W _i observed in this family.

? Genetic variability of Δ¹³C and W _i was largely independent from different temporal integration scales and their correlation was found to be strong (R ² = 88% for leaf sugars) within this family.

? Weak correlations between measures of W _i with estimators of photosynthetic capacity, suggest a minor role of the latter in the diversity of W _i.

? However, the tight correlation between g _s and Δ¹³C as well as W _i, and the related genotypic variation in stomatal density, suggest that the genotypic diversity in W _i within this pedunculate oak family might be due to differences in g _s .