Modeling photosynthesis in olive leaves under drought conditions

We quantified parameters for a model of leaf-level photosynthesis for olive, and tested the model against an independent dataset. Specific temperature-dependence parameters of the model for olive leaves were measured, as well as the relationship of the model parameters with area-based leaf nitrogen (N) content. The effect of soil water deficit on leaf photosynthesis was examined by applying two irrigation treatments to 29-year-old trees growing in a plantation: drip irrigation sufficient to meet the crop water requirements (I) and dry-farming (D). In both treatments, leaves had a higher photosynthetic capacity in April than in August. In August, photosynthetic capacity was lower in D trees than in I trees. Leaf photosynthetic capacity was linearly and positively related to leaf N content on an area basis (N(a)) and to leaf mass per unit area (LMA), and the regression slope varied with irrigation treatment. The seasonal reduction in N(a) was used in the model to predict photosynthesis under drought conditions. Olive leaves showed a clear limitation of photosynthesis by triose phosphate utilization (TPU) even at 40 degrees C, and the data suggest that olive invests fewer resources in TPU than other species. The seasonal decrease in photosynthetic capacity moderated the stomatal limitation to carbon dioxide (CO(2)) fixation as soil water deficit increased. Further, it enabled leaves to operate close to the transition point between photosynthetic limitation due to RuBP carboxylation capacity and that due to RuBP regeneration capacity, and resulted in a near constant value of internal CO(2) concentration from April to August. Under well watered conditions, N-use efficiency of the olive leaves was enhanced at the expense of reduced water-use efficiency.     

干旱胁迫对植物叶片解剖结构影响研究进展

植物在生长过程中可能会遭受干旱胁迫的影响,而叶片作为植物进行光合作用的活动中心,是在干旱胁迫条件下反应最为敏锐的器官。本文对干旱条件下植物叶片表皮结构、栅栏组织和海绵组织、叶厚度、叶脉以及气孔等结构的响应及伤害表现进行综述,以期为高等植物抗旱能力研究提供参考。     

叶面喷施外源多胺对干旱胁迫下红椿叶片解剖结构的修复效果

为了探讨叶面喷施外源多胺对干旱胁迫下红椿幼苗叶片的解剖结构损伤的修复效果,以2年生红椿家系盆栽苗为研究对象,开展了"干旱胁迫+外源多胺修复处理"试验。通过对叶片解剖结构指标的观测和分析,得出以下结果:1)3种外源多胺溶液对红椿叶片主脉直径的修复调节效果差异极显著(P <0.01);3种外源多胺溶液中,以外源精胺(Spm)溶液对植株的水分运输能力的修复效果最佳。2)3种外源多胺溶液对红椿叶片上表皮厚度起到调节效果差异不明显;3种外源多胺溶液对红椿叶片下表皮厚度修复调节效果差异显著(P <0.05);3种外源多胺溶液对红椿叶片叶肉厚度修复调节效果差异极显著(P <0.01)。结合3个指标响应的综合情况来看,3种外源多胺中以外源亚精胺(Spd)对叶片储水能力修复效果最强。3)3种外源多胺溶液对红椿叶片栅/海绵比值的修复调节效果差异极显著(P <0.01);3种外源多胺溶液中,仅外源Spd溶液对栅/海比值的缓解调节起到了明显的积极作用。     

等渗透势干旱、盐、碱胁迫下5个枣品种及酸枣的生物学响应与抗逆性

试验研究等渗透势干旱、盐、碱胁迫下枣和酸枣的生物学响应,鉴评它们对这3种主要的非生物胁迫的抗性差异.以2年生金丝小枣等5个枣品种及砧木—酸枣苗为试材,在-0.30 MPa、-1.15 MPa 2种渗透势下,设计干旱胁迫(用PEG-6 000模拟)、盐(NaCl)胁迫、碱(NaHCO3)胁迫3种逆境,以浇灌1/2Hoagland溶液、不加PEG-6000或NaCl或NaHCO3的处理为对照.生物量较生长量更能准确反映枣和酸枣对干旱、盐、碱胁迫的响应,但其中各个指标的响应存在显著差异:在植株生长量诸指标中,株高特别是冠幅的差异性很小,对胁迫种类及强度敏感度低,而枣头枝长度和基部直径对胁迫种类及强度的敏感度明显为高,是以生长量反映对胁迫响应的合适指标;在生物量诸指标中,植株叶生物量、脱落性枝生物量的响应最敏感,其次是全株生物量,茎生物量、根生物量的响应最不敏感, (叶+脱落性枝)生物量/全株生物量的响应与全株生物量的响应相似.以(叶+脱落性枝)生物量、全株生物量及(叶+脱落性枝)生物量/全株生物量3项关键指标综合评价,参试的5个枣品种及酸枣对前述逆境的抗性差异显著.其中:耐旱性最强的是大瓜枣和梨枣,耐盐性最强的是大瓜枣,耐碱性最强的是酸枣和大瓜枣.同时,5个枣品种及酸枣各自对3种逆境的响应也有明显差异:大瓜枣是一个对3种非生物逆境抗性都很优良的枣品种;冬枣既不耐干旱,也不耐盐碱,但相对而言,其耐盐性＞抗旱性＞耐碱性.枣属植物对干旱、盐、碱胁迫的抗性实际上存在很大差异.枣树引种栽培应重视品种的生理生态特性.枣优良新品种培育应关注亲本品种本身对主要逆境的抗性.     

干旱胁迫下侧柏、苦楝等树种的生理生化响应及抗旱性评价

采用盆栽试验研究干旱胁迫条件下5种树种侧柏、苦楝、栾树、黄连木、乌桕1年实生苗的抗旱生理生化指标丙二醛(MDA)、电导率(EC)、叶绿素(Chl.)、游离脯氨酸(Pro)、过氧化物酶活性(POD)等的变化。在研究生理生化指标与抗旱性关系的基础上,采用隶属函数法对上述指标进行综合分析,得出其抗旱能力从大到小的顺序为:侧柏、栾树、黄连木、乌桕、苦楝,这一结果与5种植物的实际表现一致。     

5种观赏桃F1代叶片解剖结构与光合性能研究

以5种观赏桃F1代当年生苗为实验材料,比较不同杂交组合叶片解剖结构、光合特性的差异,为杂交育种F1代的选择提供实际对比.结果表明5种F1代的叶片结构存在差异:JJ的叶肉结构指标均为最大,BM的主叶脉结构指标均为最大;气孔密度与主脉厚度均显著正相关,表明叶片气孔越多,运输系统越发达;净光合速率与主脉厚度、栅栏组织厚度、气孔密度都显著正相关,表明叶片结构对光合作用有很大的影响.     

Leaf hydraulic conductance in relation to anatomical and functional traits during Populus tremula leaf ontogeny

Leaf hydraulic conductance (K(leaf)) and several characteristics of hydraulic architecture and physiology were measured during the first 10 weeks of leaf ontogeny in Populus tremula L. saplings growing under control, mild water deficit or elevated temperature conditions. During the initial 3 weeks of leaf ontogeny, most measured characteristics rapidly increased. Thereafter, a gradual decrease in K(leaf) was correlated with a decrease in leaf osmotic potential under all conditions, and with increases in leaf dry mass per area and bulk modulus of elasticity under mild water deficit and control conditions. From about Week 3 onward, K(leaf) was 33% lower in trees subjected to mild water deficit and 33% higher in trees held at an elevated temperature relative to control trees. Mild water deficit and elevated temperature treatment had significant and opposite effects on most of the other characteristics measured. The ontogenetic maximum in K(leaf) was correlated positively with the width of xylem conduits in the midrib, but negatively with the overall width of the midrib xylem, number of lateral ribs, leaf dry mass per area and bulk modulus of elasticity. The ontogenetic maximum in K(leaf) was also correlated positively with the proportion of intercellular spaces and leaf osmotic potential, but negatively with leaf thickness, volume of mesophyll cells and epidermis and number of cells per total mesophyll cell volume, the closest relationships being between leaf osmotic potential and number of cells per total mesophyll cell volume. It was concluded that differences in protoplast traits are more important than differences in xylem or parenchymal cell wall traits in determining the variability in K(leaf) among leaves growing under different environmental conditions.     

Spatial sap flow and xylem anatomical characteristics in olive trees under different irrigation regimes

The compensation heat pulse (CHP) method is widely used to estimate sap flow and transpiration in conducting organs of woody plants. Previous studies have reported a natural azimuthal variability in sap flow, which could have practical implications in locating the CHP probes and integrating their output. Sap flow of several olive trees (Olea europaea L. cv. 'Arbequina') previously grown under different irrigation treatments were monitored by the CHP method, and their xylem anatomical characteristics were analyzed from wood samples taken at the same location in which the probes were installed. A significant azimuthal variability in the sap flow was found in a well-irrigated olive tree monitored by eight CHP probes. The azimuthal variability was well related to crown architecture, but poorly to azimuthal differences in the xylem anatomical characteristics. Well-irrigated and deficit-irrigated olive trees showed similar xylem anatomical characteristics, but they differed in xylem growth and in the ratio of nocturnal-to-diurnal sap flow (N/D index). The results of this work indicate that transpiration cannot be accurately estimated by the CHP method in olive trees if a small number of sensors are employed and that the N/D index could be used as a sensitive water status indicator.     

Clonal and seasonal differences in leaf osmotic potential and organic solutes of five hybrid poplar clones grown under field conditions

Leaf osmotic potential at full turgor (Psi(pio)) and the major solutes that contribute to osmotic potential were characterized in five hybrid poplar clones of Populus trichocarpa Torr. & Gray x P. deltoides Bartr. (TD) and P. deltoides x P. nigra L. (DN), growing under field conditions at two sites in eastern Washington and Oregon, USA. Trees were drip irrigated with 46, 76 or 137 cm of supplemental irrigation during each growing season. Trees at Wallula, WA, which were in their third growing season in 1994, were sampled twice a year for two years (1994 and 1995), and trees at Boardman, OR, which were in their second growing season in 1994, were sampled once a year for three years (1994-1996). At Wallula, the TD and DN clones exhibited lower predawn leaf water potentials in the 46-cm treatment than in the 137-cm treatment (-1.2 versus -0.7 MPa) during a hot, dry period in July 1994. Clone TD had a lower Psi(pio) than Clone DN (-1.67 versus -1.56 MPa) during the same period and the difference was also evident in 1995 (-1.81 versus -1.72 MPa) when trees were in their fourth growing season. There was also a significant treatment effect on Psi(pio) in Clone TD, with trees in the 46-cm treatment having lower Psi(pio) than trees in the 137-cm treatment in July 1994. At Boardman, Psi(pio) was generally high with no treatment differences during the 1994-96 samplings. The TD clones had significantly lower Psi(pio) than the DN clones in 1994 (-1.44 versus -1.36 MPa) and 1996 (-1.72 versus -1.54 MPa), but there was no difference between clones in 1995 (-1.40 versus -1.43 MPa). In 1995, at Wallula, osmotic adjustment in Clone TD was largely accounted for by an increase in sucrose, which constituted 70% of total organic solutes. Although the total concentration of free primary amino acids in this clone was 28% higher in trees in the 46-cm treatment than in trees in the 137-cm treatment, amino acids constituted only a small fraction of the total solute pool. Sixty-two percent of total solutes were inorganic ions in Clone TD compared to 52% in Clone DN, and potassium was the main ion constituting about 30% of total solutes and 50% of total ions. However, the clonal difference in Psi(pio) was not fully accounted for by the difference in solute concentration. Osmotic potential at full turgor declined over the growing season and with age. We conclude that, because the extent of osmotic adjustment exhibited by these clones was small, other drought resistance mechanisms contributed to the clonal differences in field performance.     

Foliar herbivory and leaf traits of five native tree species in a young plantation of Central Panama

This study examined foliar herbivory on 1 year-old tree saplings planted in previously abandoned fields in central Panama. Plots (15 × 15 trees) of Anacardium excelsum (Anacardiaceae), Dalbergia retusa (Fabaceae), Pachira quinata (Malvaceae), Tabebuia rosea (Bignoniaceae), and Terminalia amazonia (Combretaceae) were tested for herbivory using leaf counts and digital image analysis. Values of foliar carbon, foliar nitrogen, specific leaf area (SLA), and leaf toughness were analyzed to describe mechanical defenses and leaf nutrients on young and mature leaves of each of these species. For all five species, less than 10% of total leaf area was found to be damaged by arthropods. Significant (P-value < 0.001) differences in herbivory were found among both the tree species and the insect feeding guilds considered: chewing, skeletonizing, mining, and leaf-rolling. On mature leaves, Anacardium excelsum had the highest amount of leaf damage (3.53%) while Dalbergia retusa exhibited the lowest herbivore damage (1.72%). Tabebuia rosea had statistically significantly higher damage than other species for young leaves caused by leaf-rolling insects (4.21% rolling of 5.55% total damage). Leaf toughness was negatively correlated with SLA and foliar N. Linear regressions showed that herbivory was positively correlated with foliar N for young leaves and negatively correlated with foliar N for mature leaves. No statistically significant relationships were found between herbivory and the mechanical properties of toughness and SLA. Overall, results from this study indicate that, as young saplings, the species evaluated did not suffer high amounts of foliar herbivory in the plantation environment.     

Phenological investigations of different winter-deciduous species growing under Mediterranean conditions

Phenological stages are the result of biorhythms and environmental factors, these last are probably the same ones that caused, during evolution, adjustments of the species to different climate. The present study was carried out in a Phenological Garden located in central Italy (Perugia, Umbria Region) which contains indicator species, common to all International Phenological Gardens. The aim of this study was to determine and analyse the average trends of development of eight plant species and their phenological adjustment to the Mediterranean environment, over a nine-year period (1997–2005). The results of the statistical analyses show a strong relationship between the temperature trends and vegetative seasonal evolutions interpreted by phenological data for all the species considered. Moreover, it was demonstrated that the plants studied may approach or close completely the timing gaps eventually created during the first phenological phases, adjusting thus the beginning of subsequent phenophases.     

Analysis of leaf water relations in leaves of two olive (Olea europaea) cultivars differing in tolerance to salinity

One-year-old rooted cuttings of olive (Olea europaea L. cvs. Frantoio and Leccino) were grown either hydroponically or in soil in a greenhouse. Plants were exposed to NaCl treatments (0, 100, and 200 mM) for 35 days, followed by 30 to 34 days of relief from salt stress to determine whether previously demonstrated genotypic differences in tolerance to salinity were related to water relations parameters. Exposure to high salt concentrations resulted in reductions in predawn water potential (Psi(w)), osmotic potential at full turgor (Psi(piFT)), osmotic potential at turgor loss point (Psi(piTLP)), and relative water content (RWC) in both cultivars, regardless of the growth substrate. Leaf Psi(w) and RWC returned to values similar to those of controls by the end of the relief period. The effect of salinity on Psi(pi) appeared earlier in Leccino than in Frantoio. Values for Psi(piFT) were -2.50, -2.87, and -3.16 MPa for the 0, 100, and 200 mM salt-treated Frantoio plants, respectively, and -2.23, -2.87, and -3.37 MPa for the corresponding Leccino plants. Recovery of Psi(pi) was complete for plants in the 100 mM salt treatment, but not for plants in the 200 mM salt treatment, which maintained an increased pressure potential (Psi(pi)) compared to control plants. Net solute accumulation was higher in Leccino, the salt-sensitive cultivar, than in Frantoio. In controls of both cultivars, cations contributed 39.9 to 42.0% of the total Psi(piFT), mannitol and glucose contributed 27.1 to 30.8%, and other soluble carbohydrates contributed 3.1 to 3.6%. The osmotic contribution of Na(+) increased from 0.1-2.1% for non-treated plants to 8.6-15.5% and 15.6-20.0% for the 100 mM and 200 mM salt-treated plants, respectively. The mannitol contribution to Psi(piFT) reached a maximum of 9.1% at the end of the salinization period. We conclude that differences between the two cultivars in leaf water relations reflect differences in the exclusion capacities for Na(+) and Cl(-) ions.     

Seasonal variations of leaf traits and drought adaptation strategies of four common woody species in South Texas,USA

Understanding physiological responses and drought adaptation strategies of woody plant leaf traits in sub-humid to semi-arid regions is of vital importance to understand the interplay between ecological processes and plant resource-allocation strategies of different tree species.Seasonal variations of leaf morphological traits,stoichiometric traits and their relationships of two drought tolerant woody species,live oak(Quercus virginiana)and honey mesquite(Prosopis glandulosa)and two less drought tolerant species,sugarberry(Celtis laevigata)and white ash(Fraxinus americana)were analyzed in a sub-humid to semi-arid area of south Texas,USA.Our findings demonstrate that for the two drought tolerant species,the leguminous P.glandulosa had the highest specific leaf area,leaf N,P,and lowest leaf area and dry mass,indicating that P.glandulosa adapts to an arid habitat by decreasing leaf area,thus reducing water loss,reflecting a resource acquisition strategy.While the evergreen species Q.virginiana exhibited higher leaf dry mass,leaf dry matter content,C content,C:N,C:P and N:P ratios,adapts to an arid habitat through increased leaf thickness and thus reduced water loss,reflecting a resource conservation strategy in south Texas.For the two less drought tolerant deciduous species,the variations of leaf traits in C.laevigata and F.americana varied between Q.virginiana and P.glandulosa,reflecting a trade-off between rapid plant growth and nutrient maintenance in a semi-arid environment.     

Influence of ozone and nitrogen deposition on bark beetle activity under drought conditions

Four years of severe drought from 1999 through 2003 led to unprecedented bark beetle activity in ponderosa and Jeffrey pine in the San Bernardino and San Jacinto Mountains of southern California. Pines in the San Bernardino Mountains also were heavily impacted by ozone and nitrogenous pollutants originating from urban and agricultural areas in the Los Angeles basin. We studied bark beetle activity and bark beetle associated tree mortality in pines at two drought-impacted sites in the San Bernardino Mountains, one receiving high levels of atmospheric pollutants, and one with more moderate atmospheric input. We also investigated the effects of nitrogen addition treatments of 0, 50 and 150 kg N ha⁻¹ year⁻¹ at each site. Tree mortality and beetle activity were significantly higher at the high pollution site. Differences in beetle activity between sites were significantly associated with ozone injury to pines, while differences in tree mortality between sites were significantly associated with both ozone injury and fertilization level. Tree mortality was 9% higher and beetle activity 50% higher for unfertilized trees at the high pollution site compared to the low pollution site. Tree mortality increased 8% and beetle activity increased 20% under the highest rates of nitrogen additions at the low pollution site. The strong response in beetle activity to nitrogen additions at the low pollution site suggests that atmospheric nitrogen deposition increased tree susceptibility to beetle attack at the high deposition site. While drought conditions throughout the region were a major factor in decreased tree resistance, it appears that both ozone exposure and atmospheric nitrogen deposition further increased pine susceptibility to beetle attack.     

Gas exchange, leaf structure and nitrogen in contrasting successional tree species growing in open and understory sites during a drought

Seasonal ecophysiology, leaf structure and nitrogen were measured in saplings of early (Populus grandidentata Michx. and Prunus serotina J.F. Ehrh.), middle (Fraxinus americana L. and Carya tomentosa Nutt.) and late (Acer rubrum L. and Cornus florida L.) successional tree species during severe drought on adjacent open and understory sites in central Pennsylvania, USA. Area-based net photosynthesis (A) and leaf conductance to water vapor diffusion (g(wv)) varied by site and species and were highest in open growing plants and early successional species at both the open and understory sites. In response to the period of maximum drought, both sunfleck and sun leaves of the early successional species exhibited smaller decreases in A than leaves of the other species. Shaded understory leaves of all species were more susceptible to drought than sun leaves and had negative midday A values during the middle and later growing season. Shaded understory leaves also displayed a reduced photosynthetic light response during the peak drought period. Sun leaves were thicker and had a greater mass per area (LMA) and nitrogen (N) content than shaded leaves, and early and middle successional species had higher N contents and concentrations than late successional species. In both sunfleck and sun leaves, seasonal A was positively related to predawn leaf Psi, g(wv), LMA and N, and was negatively related to vapor pressure deficit, midday leaf Psi and internal CO(2). Although a significant amount of plasticity occurred in all species for most gas exchange and leaf structural parameters, middle successional species exhibited the largest degree of phenotypic plasticity between open and understory plants.     

Effects of ontogenetic stage and leaf age on leaf functional traits and the relationships between traits in Pinus koraiensis

Investigating the effects of ontogenetic stage and leaf age on leaf traits is important for understanding the utilization and distribution of resources in the p...     

Carbon and phosphorus partitioning in Pinus serotina seedlings growing under hypoxic and low-phosphorus conditions

Ten-week-old pond pine (Pinus serotina Michx.) seedlings were grown in solution culture at 5 or 100 microM P and under aerobic or hypoxic solution conditions. After 6 and 10 weeks in the treatments, changes in relative growth rate (RGR), P acquisition and allocation, and carbohydrate partitioning were determined by analyzing tissue for total P, soluble sugars and starch. Six weeks of low-P growth conditions decreased seedling dry weight and the ratio of shoot dry weight to root dry weight (S/R) by 39 and 51%, respectively, in comparison to seedlings from the aerobic, high-P (control) treatment. Mean RGRs of shoots in the low-P treatment were reduced by 33%, whereas root growth was unaffected. After 10 weeks of low-P growth conditions, however, both shoot and root RGRs were significantly reduced, and plants had lower S/R ratios than in any other treatment. Slowed shoot growth was accompanied by starch and nonstructural carbohydrate accumulation in needles, indicating that needle growth was not limited by carbohydrate supply. Six weeks of low-P growth conditions decreased total seedling P by 75%, reflecting a 97% reduction in the net uptake rate (NUR). Shoot NUR as a fraction of seedling NUR was also greatly reduced in the low-P treatment, indicating that low-P growth conditions affected P translocation to the shoot more than P accumulation by roots. In contrast, 6 weeks of hypoxic growth conditions decreased total dry weight of seedlings in the high-P treatment by 41% relative to their aerobic counterparts. Root growth was affected more than shoot growth, however, and S/R ratios increased. After 10 weeks, S/R ratios doubled, primarily because of the reduction in root RGR. Nevertheless, roots of hypoxic seedlings contained a higher percentage of total seedling P than their aerobic counterparts. Net P acquisition per seedling decreased by more than 50% under hypoxic growth conditions, as a result of reductions in both root RGR and seedling NUR. Starch accumulation in shoots of hypoxic seedlings reflected reductions both in root growth and in transport of carbohydrates to nonwoody roots. Carbohydrate availability did not appear to be limiting growth of hypoxic woody roots, which are well-aerated internally, but it may have limited metabolic processes in nonwoody roots of seedlings from the high-P treatment.     

银杏不同品种生长及耐旱性的比较

对6个银杏品种7 a生幼树的树高、干径、1 a生枝长及离体叶片的相对含水量(RWC)和叶绿素稳定指数(CSI)进行研究,结果表明,不同品种的干径和1 a生枝长度的差异达到了极显著水平,干径以大佛手最粗,为2.0824 cm,马铃最细,仅为1.5378 cm;1 a生枝长度最长的是大圆铃达22.9773 cm,最短的是郯城9号,仅为12.0889 cm;马铃的耐旱性最强,CSI为20.67,RWC损失率为65.07%。