红树林植物叶片形态和解剖特征对叶肉导度、叶片导水率的影响

叶肉导度和叶片导水率是影响光合作用的两个重要过程,叶肉导度通过影响从气孔下腔到Rubisco酶位点的二氧化碳浓度梯度直接影响光合作用,而叶片导水率则通过影响水分供应或气孔行为来影响光合作用,然而对这两个生理过程之间的协同性研究较少。本研究选择9种红树林植物为研究对象,探讨盐生环境下植物叶肉导度和叶片导水率的协同性及其与叶片解剖结构特征之间的相关性。结果表明,9种红树林植物叶片导水率(0.78~5.83 mmol·m~(-2)·s~(-1)·MPa-1)、叶肉导度(0.06~0.36 mol·m~(-2)·s~(-1))、最大光合速率(7.23~23.71μmol·m~(-2)·s~(-1))等特征的差别较大;叶肉导度与最大光合速率呈显著正相关,而与比叶重无显著相关性,其原因是由于比叶重与叶片厚度、叶片密度不存在相关性;叶脉密度与气孔密度呈较强的相关性,说明红树林植物叶片水分运输与散失相关的叶片结构之间存在协同关系;叶片导水率不受叶脉密度影响,并且与叶肉导度、最大光合速率也不存在相关性,这很可能与红树林植物叶片的肉质化、有发达的储水组织有关,体现了红树林植物叶片结构和功能的特殊性。     

工厂化黄瓜穴盘育苗昼温适应性

在人工气候室内以黄瓜穴盘苗为材料,测定不同昼温处理下(昼温分别为30℃、27℃、24℃、21℃、18℃、15℃,夜温均为15℃)黄瓜幼苗下胚轴长、下胚轴粗、第一叶片和第二叶片的长和宽、地上部和地下部干物质积累量、叶片含水率及叶片的叶绿素荧光特性,并用主成分分析法和聚类分析法对不同昼温处理下的黄瓜穴盘苗质量进行分析.结果表明:不同昼温处理下黄瓜穴盘苗各生长指标存在显著性差异,幼苗质量的昼温反应表现为24℃＞21℃＞27℃＞30℃＞18℃＞15℃;通过主成分分析和系统聚类可以把各温度处理分为:最适温度处理(24℃/15℃)、适宜温度处理(21℃/15℃)和不适宜温度处理3类;不适宜温度处理又可分为高温抑制类(27C/15℃,30℃/15℃)和低温抑制类(15℃/15℃,18℃/15℃)2类.     

环境和遗传对烟草叶片结构的影响

叶片性状很大程度上反映了植物的功能及其对环境的适应。叶片性状的变异受环境及遗传特性的影响,但是很多研究未能很好区分出它们的相对影响。本研究通过将同一烟草品种种植于不同地点来认识环境对烟草叶片性状的影响;将不同的烟草品种种植于同一环境来了解遗传差异对烟草叶片性状的影响。研究发现,叶脉密度和叶片厚度受环境的影响较大,气孔密度和长度受环境的影响较小。气孔密度和叶片厚度受遗传的影响较大,叶脉密度和气孔长度受遗传的影响较小。在生长温度高的地方,烟草叶脉密度越大。研究结果对于认识植物对环境的适应性具有重要意义。     

生长温度对烟草叶片环式电子传递活性的影响

高等植物的光合机构在环境胁迫条件下非常容易产生光抑制,环式电子传递在光合机构的光保护中发挥着重要的作用.但是,生长温度对环式电子传递的影响并不清楚.本研究测定了在24/18℃和32/26℃条件下生长40天的烟草(K326)叶片的气体交换、叶绿素荧光和P700氧化还原态的光响应曲线.结果表明,烟草叶片在两种生长温度下的的光合能力、光化学淬灭、非光化学淬灭和通过光系统Ⅱ的电子传递速率(ETR Ⅱ)均没有差异.但是,在强光条件下,生长在24/18℃的叶片比生长在32/26℃的具有更高的通过光系统Ⅰ的电子传递速率(ETRⅠ)和ETRⅠ/ETR Ⅱ比值.短时间的强光处理后,生长在24/18℃的叶片具有较高的光系统Ⅱ最大量子产额(Fv/Fm),表明环式电子传递活性的上调有助于缓解生长在24/18℃的叶片光系统Ⅱ受到的光损伤.综上所述,环式电子传递活性的增强是植物适应较低生长温度的重要策略.     

生长温度对烟草叶片环式电子传递活性的影响（英文）

高等植物的光合机构在环境胁迫条件下非常容易产生光抑制,环式电子传递在光合机构的光保护中发挥着重要的作用。但是,生长温度对环式电子传递的影响并不清楚。本研究测定了在24/18℃和32/26℃条件下生长40天的烟草(K326)叶片的气体交换、叶绿素荧光和P700氧化还原态的光响应曲线。结果表明,烟草叶片在两种生长温度下的的光合能力、光化学淬灭、非光化学淬灭和通过光系统II的电子传递速率(ETR II)均没有差异。但是,在强光条件下,生长在24/18℃的叶片比生长在32/26℃的具有更高的通过光系统I的电子传递速率(ETR I)和ETR I/ETR II比值。短时间的强光处理后,生长在24/18℃的叶片具有较高的光系统II最大量子产额(Fv/Fm),表明环式电子传递活性的上调有助于缓解生长在24/18℃的叶片光系统II受到的光损伤。综上所述,环式电子传递活性的增强是植物适应较低生长温度的重要策略。     

叶脉结构与功能及其对叶片经济谱的影响

叶脉由贯穿于叶肉内部的维管组织及其外围机械组织构成, 多样化的脉序及网络结构使叶脉系统发生变异和功能分化。该文综述了叶脉系统结构与功能的最新研究进展。通过聚焦叶脉分级系统的结构与功能及其在叶片经济谱(LES)中的重要性, 解释叶脉性状与其它叶片功能性状之间的关系及机制。不同等级叶脉在机械支撑与水分运输方面存在功能分化, 其中1-3级粗脉在维持叶片形状和叶表面积以及物理支撑方面发挥重要作用, 有利于维持叶片最大受光面积; 4级及以上细脉具有水分调节功能, 它们与气孔相互协调, 影响叶片水分运输、蒸腾散热和光合作用速率。叶片生长过程与叶脉发育的动态变化模式决定叶脉密度, 并影响叶脉密度与叶片大小之间的关系: 叶面积与粗脉密度呈显著负相关, 与粗脉直径呈显著正相关, 而与细脉密度无关。与叶脉性状相关的叶片经济谱框架模型预测, 叶脉密度较高的叶片寿命短、比叶重较小, 叶片最大碳同化速率、代谢速率以及资源获取策略潜力较高。     

不结球白菜表皮蜡质高温胁迫生理响应

为了明晰高温胁迫下表皮蜡质在不结球白菜生理响应中的保护作用,该研究以不结球白菜有蜡(Q28)和无蜡(Q1202)品种为试验材料,设置高温胁迫组(昼/夜温度为37℃/30℃)和对照组(昼/夜温度为25℃/18℃)处理,观察不同材料叶片表皮细胞形态,比较分析高温胁迫处理下不同时期生理和光合指标变化的差异.结果 表明:(1)...     

植物叶片导水率的研究进展

植物叶片的水分传输是SPAC系统中的一个重要环节,不仅受植物本身的调节和控制,而且还受外界环境条件的影响,是复杂的生理过程。为了搞清SPAC系统水分传输机理,人们对植物叶片导水率进行了大量的研究。本文综述了近年来植物体叶片导水率研究的一些新的进展和发展动态,就叶片水分传输在植物水分平衡中的作用、叶片导水率的定义及其影响因素等方面进行了综述。影响植物叶片导水率的内部、外部环境因素各异,文章重点阐述了土壤因素、气象因素、植物激素、生育阶段和解剖特性等对叶片导水率的影响,提出植物叶片导水率研究中亟需考虑的问题,并对今后SPAC系统中叶片导水率研究的重点发展方向做了展望。     

润楠属植物叶片和枝条水力特征的协同关系

以润楠属(Machilus) 7种植物成年个体为材料,对其进行生理指标测定,并对它们的叶片水分供需关系以及木质部纹孔特征和导水效率之间的关联进行分析。结果显示,润楠属7种植物相比原始被子植物具有更高的叶脉密度(VD),叶脉密度为9.8～14.1 mm/mm~2;气孔密度(SD)与叶脉密度呈显著正相关,说明叶片水分供需存在协同关系;气孔密度与气孔大小(GLC)呈负相关;气孔越大的叶片其膨压丧失点(TLP)的绝对值越低。枝条边材比导率(Ks)较低,为0.13～1.87 kg·m~(-1)·s~(-1)·MPa~(-1),且种间差异较大。叶脉和气孔密度均与边材比导率呈正相关。边材比导率与纹孔膜面积、纹孔口面积以及纹孔口长短轴比例相关性不显著。研究结果表明润楠属植物虽然叶脉密度较高,且木质部水分供应和叶片结构具有协同关系,但木质部解剖结构较为原始,导管多具梯形穿孔板,导水效率低,只能适应比较湿润的生境。     

热带雨林木质藤本植物叶片性状及其关联

热带雨林中木质藤本植物较为丰富。随着全球气候变化加剧,木质藤本植物的丰富度具有不断增加的趋势,有可能对热带森林的结构、功能和动态产生重要影响。然而,目前对木质藤本响应环境变化的机制所知甚少。本研究以13个科20种热带雨林常见木质藤本植物为材料,测定了冠层叶片的17个形态特征及结构性状,并分析了性状间的相互关系。结果表明,叶片相对含水量的种间变异最小（变异系数为5%）,而上表皮厚度的种间变异最大（变异系数为80%）,其它性状的种间变异系数为24%~61%。木质藤本植物的叶脉密度、叶片密度均与气孔密度呈显著正相关,叶片干物质含量与比叶面积呈显著负相关。与相同生境的树木相比,木质藤本的叶面积更小、气孔密度和叶片密度更低、比叶面积更高,但两种植物类群的叶片横切面组织结构厚度无显著差异。研究结果对理解木质藤本植物的生态适应性具有重要意义。     

Effects of temperature on leaf hydraulic architecture of tobacco plants

Main Conclusion

Modifications in leaf anatomy of tobacco plants induced greater leaf water transport capacity, meeting greater transpirational demands and acclimating to warmer temperatures with a higher vapor pressure deficit. Temperature is one of the most important environmental factors affecting photosynthesis and growth of plants. However, it is not clear how it may alter leaf hydraulic architecture. We grew plants of tobacco (Nicotiana tabacum) ‘k326’ in separate glasshouse rooms set to different day/night temperature conditions: low (LT 24/18 °C), medium (MT 28/22 °C), or high (HT 32/26 °C). After 40 days of such treatment, their leaf anatomies, leaf hydraulics, photosynthetic rates, and instantaneous water-use efficiency (WUE_i) were measured. Compared with those under LT, plants exposed to HT or MT conditions had significantly higher values for minor vein density (MVD), stomatal density (SD), leaf area, leaf hydraulic conductance (K _leaf), and light-saturated photosynthetic rate (A _sat), but lower values for leaf water potential (ψ _l) and WUE_i. However, those parameters did not differ significantly between HT and MT conditions. Correlation analyses demonstrated that SD and K _leaf increased in parallel with MVD. Moreover, greater SD and K _leaf were partially associated with accelerated stomatal conductance. And then stomatal conductance was positively correlated with A _sat. Therefore, under well-watered, fertilized conditions, when relative humidity was optimal, changes in leaf anatomy seemed to facilitate the hydraulic acclimation to higher temperatures, meeting greater transpirational demands and contributing to the maintenance of great photosynthetic rates. Because transpiration rate increased more with temperature than photosynthetic rate, WUE_i reduced under warmer temperatures. Our results indicate that the modifications of leaf hydraulic architecture are important anatomical and physiological strategies for tobacco plants acclimating to warmer temperatures under a higher vapor pressure deficit.     

亚低温与干旱胁迫对番茄植株水分传输和形态解剖结构的影响

为探讨亚低温和干旱对植株水分传输的影响机制,以番茄幼苗为试材,利用人工气候室设置常温(昼25 ℃/夜18 ℃)和亚低温(昼15 ℃/夜8 ℃)环境,采用盆栽进行正常灌水(75%～85%田间持水量)和干旱处理(55%～65%田间持水量),分析了温度和土壤水分对番茄植株水分传输、气孔和木质部导管形态解剖结构的影响。结果表明: 与常温正常灌水处理相比,干旱处理使番茄叶水势、蒸腾速率、气孔导度、水力导度、茎流速率、气孔长度和叶、茎、根导管直径显著减小,而使叶、茎、根导管细胞壁厚度和抗栓塞能力增强;亚低温处理下番茄叶水势、蒸腾速率、气孔导度、水力导度和叶、茎、根导管直径显著降低,但气孔变大,叶、根导管细胞壁厚度和叶、茎、根抗栓塞能力显著升高。亚低温条件下土壤水分状况对番茄叶水势、蒸腾速率、气孔导度、水力导度、气孔形态、叶、根导管结构均无显著影响。总之,干旱处理下番茄通过协同调控叶、茎、根结构使植株水分关系重新达到稳态;亚低温处理下番茄植株水分关系的调控主要通过改变叶和根导管结构实现,且受土壤水分状况的影响较小。     

Potassium mediates coordination of leaf photosynthesis and hydraulic conductance by modifications of leaf anatomy

Typical symptoms of potassium deficiency, characterized as chlorosis or withered necrosis, occur concomitantly with downregulated photosynthesis and impaired leaf water transport. However, the prominent limitations and mechanisms underlying the concerted decreases of leaf photosynthesis and hydraulic conductance are poorly understood. Monocots and dicots were investigated based on responses of photosynthesis and hydraulic conductance and their components and the correlated anatomical determinants to potassium deficiency. We found a conserved pattern in which leaf photosynthesis and hydraulic conductance concurrently decreased under potassium starvation. However, monocots and dicots showed two different hydraulic‐redesign strategies: Dicots tended to show a decreased minor vein density, whereas monocots reduced the size of the bundle sheath and its extensions, rather than the minor vein density; both of these strategies may restrain xylem and outside‐xylem hydraulic conductance. Additionally, potassium‐deprived leaves developed with fewer mesophyll cell‐to‐cell connections, leading to a reduced area being available for liquid‐phase flow. Further quantitative analysis revealed that mesophyll conductance to CO₂ and outside‐xylem hydraulic resistance were the major contributors to photosynthetic limitation and increased hydraulic resistance, at more than 50% and 60%, respectively. These results emphasize the importance of potassium in the coordinated regulation of leaf photosynthesis and hydraulic conductance through modifications of leaf anatomy.     

Differential leaf expansion can enable hydraulic acclimation to sun and shade

Although leaf size is one of the most responsive plant traits to environmental change, the functional benefits of large versus small leaves remain unclear. We hypothesized that modification of leaf size within species resulting from differences in irradiance can allow leaves to acclimate to different photosynthetic or evaporative conditions while maintaining an efficient balance between hydraulic supply (vein density) and evaporative demand. To test this, we compared the function and anatomy of leaf hydraulic systems in the leaves of a woody angiosperm (Toona ciliata M. Roem.) grown under high and low irradiance in controlled conditions. Our results confirm that in this species, differential leaf expansion regulates the density of veins and stomata such that leaf hydraulic conductance and stomatal conductance remain proportional. A broader sample of field-grown tree species suggested that differences in leaf venation and stomatal traits induced by sun and shade were not regulated by leaf size in all cases. Our results, however, suggest that leaf size plasticity can provide an efficient way for plants to acclimate hydraulic and stomatal conductances to the contrasting evaporative conditions of sun and shade.     

Characteristics of “Number of Veins” to Estimate Leaf Maturity in Pteris mutilata (Pteridaceae)

Pteris mutilata , as has been established in ferns of cool temperate regions. NV expressed developmental stages better than any other leaf size parameters, such as blade length, blade width, stipe length, and total length (blade+stipe length). The leaf shape became more oblong and/or slender after the plant matured, which could be measured by two shape parameters, (blade width)/(total length) and (blade width)/(blade length). Principal component analysis using all the morphological parameters showed that NV is categorized into size parameters, although NV has been considered to differ somehow from the other size parameters. Thus NV represents one of the size parameters that is the most appropriate to estimate leaf maturation. Received 6 July 2000/ Accepted in revised form 22 August 2000     

Decline of leaf hydraulic conductance with dehydration: relationship to leaf size and venation architecture

Across plant species, leaves vary enormously in their size and their venation architecture, of which one major function is to replace water lost to transpiration. The leaf hydraulic conductance (K(leaf)) represents the capacity of the transport system to deliver water, allowing stomata to remain open for photosynthesis. Previous studies showed that K(leaf) relates to vein density (vein length per area). Additionally, venation architecture determines the sensitivity of K(leaf) to damage; severing the midrib caused K(leaf) and gas exchange to decline, with lesser impacts in leaves with higher major vein density that provided more numerous water flow pathways around the damaged vein. Because xylem embolism during dehydration also reduces K(leaf), we hypothesized that higher major vein density would also reduce hydraulic vulnerability. Smaller leaves, which generally have higher major vein density, would thus have lower hydraulic vulnerability. Tests using simulations with a spatially explicit model confirmed that smaller leaves with higher major vein density were more tolerant of major vein embolism. Additionally, for 10 species ranging strongly in drought tolerance, hydraulic vulnerability, determined as the leaf water potential at 50% and 80% loss of K(leaf), was lower with greater major vein density and smaller leaf size (|r| = 0.85-0.90; P < 0.01). These relationships were independent of other aspects of physiological and morphological drought tolerance. These findings point to a new functional role of venation architecture and small leaf size in drought tolerance, potentially contributing to well-known biogeographic trends in leaf size.     

Vein recovery from embolism occurs under negative pressure in leaves of sunflower (Helianthus annuus)

Leaf veins undergo cavitation at water potentials (Psi(leaf)) commonly experienced by field-growing plants. Theoretically, embolism reversal should not be possible until xylem pressures rise by several kilopascals of atmospheric pressure, but recent evidence suggests that embolized conduits can be refilled even when surrounded by others at substantial tension (novel refilling). The present study reports 'novel refilling' occurring in leaf veins of sunflower (Helianthus annuus L.) while at Psi(leaf) = -0.33 MPa. Sixty per cent loss of vein hydraulic conductance (K(vein)) was recorded at Psi(leaf) < -0.65 MPa, while stem hydraulic conductance (K(stem)) was unaffected even at Psi(leaf) = -1.1 MPa. Loss of K(vein) was accompanied by stomatal closure. Water-stressed plants (Psi(leaf) = -1.1 MPa) were rehydrated overnight to different target water potentials achieved by using PEG at different concentrations as irrigation medium. K(vein) recovered by 50% at Psi(leaf) = -0.47 MPa and vein refilling was complete at Psi(leaf) = -0.33 MPa, i.e. well below the theoretical limit for conduit refilling (-0.05 MPa as calculated for sunflower minor veins). Mercurials supplied to detached leaves had no effect on the refilling process. Upon rehydration, recovery of K(vein) was not paralleled by recovery of whole-plant hydraulic conductance or leaf conductance to water vapour (g(L)), as a likely consequence of hydraulic failure of other components of the water pathway (root system or extravascular leaf compartments) and/or root-to-leaf chemical signalling. This is the first study providing experimental evidence for 'novel refilling' in a herbaceous dicot and highlighting the importance of this process in the leaf.     

Hydraulic conductance as a factor limiting leaf expansion of phosphorus-deficient cotton plants

Suboptimal levels of phosphorus (P) strongly inhibited leaf expansion in young cotton (Gossypium hirsutum L.) plants during the daytime, but had little effect at night. The effect of P was primarily on cell expansion. Compared to plants grown on high P, plants grown on low P had lower leaf water potentials and transpiration rates, and greater diurnal fluctuations in leaf water potential. Hydraulic conductances of excised root systems and of intact transpiring plants were determined from curves relating water flow rate per unit root length to the pressure differential across the roots. Both techniques showed that low P significantly decreased root hydraulic conductance. The effects of P nutrition on hydraulic conductance preceded effects on leaf area. Differences in total root length, shoot dry weight, and root dry weight all occurred well after the onset of differences in leaf expansion. The data strongly indicate that low P limits leaf expansion by decreasing the hydraulic conductance of the root system.