Leaf Lateral Asymmetry in Morphological and Physiological Traits of Rice Plant

Leaf lateral asymmetry in width and thickness has been reported previously in rice. However, the differences between the wide and narrow sides of leaf blade in other leaf morphological and physiological traits were not known. This study was conducted to quantify leaf lateral asymmetry in leaf width, leaf thickness, specific leaf weight (SLW), leaf nitrogen (N) concentration based on dry weight (Nw) and leaf area (Na), and chlorophyll meter reading (SPAD). Leaf morphological and physiological traits of the two lateral halves of the top three leaves at heading stage were measured on 23 rice varieties grown in three growing seasons in two locations. Leaf lateral asymmetry was observed in leaf width, leaf thickness, Nw, Na, and SPAD, but not in SLW. On average, the leaf width of the wide side was about 17% higher than that of the narrow side. The wide side had higher leaf thickness than the narrow side whereas the narrow side had higher Nw, Na, and SPAD than the wide side. We conclude that the narrow side of leaf blade maintained higher leaf N status than the wide side based on all N-related parameters, which implies a possibility of leaf lateral asymmetry in photosynthetic rate in rice plant.     

中亚热带樟科3种植物幼苗叶结构型性状的种间差异及其相关性

为了揭示植物叶功能性状对全球气候变化的响应和适应规律,以樟科3种植物幼苗为研究对象,将其人工采集的种子经低温沙藏并于温室培育,然后将幼苗移栽到野外同质园中自然生长,研究中亚热带樟科植物刨花楠(Machilus pauhoi)、香樟(Cinnamomum camphora)和闽楠(Phoebe bournei)两年生幼苗生长季节9种叶结构型性状的种间差异及其相关性。结果显示,(1)在3种植物幼苗中,香樟叶面积、叶厚度、叶体积、叶氮磷比最大,叶氮浓度最高,叶组织密度最小;闽楠叶组织密度、叶干物质含量最大,叶磷浓度最高,叶面积、叶体积、比叶面积、叶氮磷比最小,叶氮浓度最低;刨花楠比叶面积最大,叶厚度、叶干物质含量最小,叶磷浓度最低;3种植物幼苗的叶厚度之间均无显著差异。(2)Pearson相关分析和线性回归分析结果表明,樟科3种植物幼苗的叶面积与叶体积间呈极显著正相关(P0.01)、与叶干物质含量间呈极显著负相关(P0.01)、与叶磷浓度间呈极显著负相关(P0.01)、与叶组织密度间呈显著负相关(P0.05)、与叶氮浓度间呈显著正相关(P0.05);叶厚度与比叶面积间呈显著负相关(P0.05)、与叶干物质含量间呈显著正相关(P0.05);叶体积与叶组织密度间呈极显著负相关(P0.01)、与叶氮浓度间呈极显著正相关(P0.01)、与叶磷浓度间呈显著负相关(P0.05);叶组织密度与叶磷浓度间呈显著正相关(P0.05);比叶面积与叶干物质含量间呈极显著负相关(P0.01)、与叶磷浓度间呈极显著负相关(P0.01);叶干物质含量与叶磷浓度间呈极显著正相关(P0.01)。这表明在同质园中生长的刨花楠、香樟和闽楠幼苗的9种叶结构型性状表现出一定的种间差异,不同物种同一叶结构型性状指标的大小顺序、种间差异及其显著性不同;3种植物幼苗不同叶结构型性状之间的相关性及其显著程度也不同。本研究结果为揭示樟科3种植物幼苗叶功能性状对全球气候变化的响应和适应规律提供了基础数据。     

燕麦植株生长及叶片生理活性对土壤镉胁迫的响应

该研究以燕麦品种‘燕科2号’(籽粒镉积累量高,Yh)和‘200919 7 1’(籽粒镉积累量低,Yl)为材料,采用盆栽试验,在土壤Cd胁迫条件下测定两种类型燕麦植株生长、叶片光合生理参数及抗氧化酶活性的变化,探讨两品种对Cd胁迫的响应差异。结果表明：(1)Cd胁迫条件下,燕麦品种Yh和Yl植株生长、气体交换参数及叶绿素荧光参数均受到抑制,并以单株干重、叶片净光合速率(P_n)、光化学淬灭系数(qP)表现最为突出,Yh的降幅分别为38.2%、35.0%、14.7%,Yl降幅分别为40.8%、57.1%、27.3%。(2)镉胁迫均诱导增强了两个类型燕麦品种叶片抗氧化酶活性,尤其是SOD活性得到显著增强,Yh和Yl的增幅分别为41.9%和44.9%; Cd胁迫也显著提高了MDA含量,Yh和Yl的增幅分别达到22.2%和18.1%。研究发现,在Cd胁迫条件下,与低Cd积累燕麦品种相比,高Cd积累燕麦品种具有较高的生物量和抗氧化酶活性,以及较强的净光合速率和优异的叶绿素荧光特性,从而表现出较强的耐Cd性。     

Differences in Leaf Flammability,Leaf Traits and Flammability-Trait Relationships between Native and Exotic Plant Species of Dry Sclerophyll Forest

The flammability of plant leaves influences the spread of fire through vegetation. Exotic plants invading native vegetation may increase the spread of bushfires if their leaves are more flammable than native leaves. We compared fresh-leaf and dry-leaf flammability (time to ignition) between 52 native and 27 exotic plant species inhabiting dry sclerophyll forest. We found that mean time to ignition was significantly faster in dry exotic leaves than in dry native leaves. There was no significant native-exotic difference in mean time to ignition for fresh leaves. The significantly higher fresh-leaf water content that was found in exotics, lost in the conversion from a fresh to dry state, suggests that leaf water provides an important buffering effect that leads to equivalent mean time to ignition in fresh exotic and native leaves. Exotic leaves were also significantly wider, longer and broader in area with significantly higher specific leaf area–but not thicker–than native leaves. We examined scaling relationships between leaf flammability and leaf size (leaf width, length, area, specific leaf area and thickness). While exotics occupied the comparatively larger and more flammable end of the leaf size-flammability spectrum in general, leaf flammability was significantly correlated with all measures of leaf size except leaf thickness in both native and exotic species such that larger leaves were faster to ignite. Our findings for increased flammability linked with larger leaf size in exotics demonstrate that exotic plant species have the potential to increase the spread of bushfires in dry sclerophyll forest.     

植物叶片衰老的分子机制

文章就叶片衰老过程中基因表达调控机制的研究进展作了介绍     

Cultural Differences and Urban Spatial Forms: Elements of Boundedness in an Accra Community

In this article, I expand on Coquery-Vidrovitch's observation (1991) that to understand each African urban milieu, we must view it as more than a fusion of European, American, or traditional culture. Rather, we must see each African city as unique, that is, in fact, internally differentiated, containing a multitude of enclaves that vary one from another in their respective social, physical, and architectural spatial forms. I focus on one community in Accra known as Sabon Zongo. Founded by migrant Hausa from northern Nigeria almost a century ago, it is neither typically southern Ghanaian nor Hausa, having adapted to a mixed cultural milieu. Laid out by the British as part of their town plan, its manner of growth has blurred the original scheme. I examine a number of components that define the uniqueness of this particular urban community, including physical delineations (within Sabon Zongo and between it and the city at large), local knowledge, the landscape, the infrastructure, market and street trade, and centripetal socio-spatial structures such as the family compound. [Ghana, zongo, social-spatial linkage]     

The Relationship Between Leaf Thickness and Plant Water Potential

Leaf thickness was continuously measured in a wide range ofenvironments using a new type of displacement transducer whichis easy to set-up and automatically compensates for the effectsof temperature. Simultaneous measurements were made of waterpotential using either a psychrometer attached to the leaf petioleor a leaf pressure chamber. Thickness of leaves was a sensitiveindicator of plant water status but calibrations against anindependent method were necessary in every plant for accurateestimates of water potential. The relationship between leafthickness changes and water potential, measured in detachedleaves, was usually curvilinear and was strongly influencedby leaf age, stress history and, in young leaves, by the effectsof leaf growth. Leaf thickness growth was absent in mature cabbageleaves. Key words: Leaf thickness, plant water potential, psychrometer     

互花米草与芦苇耐盐生理特征的比较分析

以天津滨海滩涂外来植物互花米草和本地种芦苇为研究对象,对两种植物根、茎、叶3个器官保护酶(超氧化物歧化酶(SOD)、过氧化物酶（POD）、过氧化氢酶(CAT))和膜脂过氧化产物丙二醛(MDA)、游离脯氨酸、可溶性糖以及质膜相对透性及其季节动态变化进行了测定。结果表明：（1）互花米草体内SOD、POD、CAT酶活性、游离脯氨酸、可溶性糖含量在整个生长季节较芦苇偏低;（2）游离脯氨酸和可溶性糖是互花米草和芦苇体内重要的有机渗透调节物质;(3)两种植物根、茎、叶的质膜相对透性在整个生长季节基本保持稳定,但互花米草质膜相对透过性高于芦苇。该研究有利于解释互花米草适应潮间带生存环境的部分机制,并且从生理生态学特性角度说明其竞争力高于芦苇的原因。     

The Leaf Movements of Soybean, a Short-day Plant

If Bünning is correct in supposing that illumination ofa short-day plant during its skotophases prevents its generalmetabolism from reaching the normal ‘skotophile maximum’,leaf movements, too, should be diminished in non-inductive daylengths.‘Biloxi’ soybean is a well-known short-day plantand its leaflets show pronounced movement between day and night.However, measurement of the angle between the day and nightpositions of the leaves did not reveal any difference in longand short days.     

The Scaling Relationships between Leaf Mass and Leaf Area of Vascular Plant Species Change with Altitude

The scaling relationship between leaf dry mass and leaf surface area has important implications for understanding the ability of plants to harvest sunlight and grow. Whether and how the scaling relationships vary across environmental gradients are poorly understood. We analyzed the scaling relationships between leaf mass and leaf area of 121 vascular plant species along an altitudinal gradient in a subtropical monsoon forest. The slopes increased significantly with altitude, it varied from less than 1 at low altitude to more than 1 at high altitude. This means that plants growing at high altitude allocate proportionately more biomass to support tissues in larger leaves and less in smaller leaves, whereas the reverse is true at low altitude. This pattern can be explained by different leaf strategies in response to environmental pressure and constrains.     

植物叶片衰老与氧化胁迫

叶片衰老是叶片生长发育进程中的最后阶段,与活性氧伤害有着密切的关系。介绍了植物叶片衰老过程中活性氧产生及清除系统的变化,讨论了对水分胁迫与氧化胁迫的交叉抗性,并对下一步的研究作出了展望     

植物叶片衰老与氧化胁迫

叶片衰老是叶片生长发育进程中的最后阶段,与活性氧伤害有着密切的关系。介绍了植物叶片衰老过程中活性氧产生及清除系统的变化,讨论了对水分胁迫与氧化胁迫的交叉抗性,并对下一步的研究作出了展望。     

Comparison of Chlorophyll Meter Readings with Leaf Chlorophyll Concentration in Amaranthus vlitus: Correlation with Physiological Processes1

The portable chlorophyll meter (SPAD-502) has been successfully used for a rapid and direct estimation of total chlorophyll content (TCHL) in the leaves of some crops. In this work, SPAD-502 meter readings and TCHL concentration were compared for the leaves of Amaranthus vlitus L., a common weed. SPAD readings were linearly and positively correlated to TCHL concentration in the leaves. A linear correlation was also shown between SPAD-502 readings and some physiological parameters of the leaves, such as photosynthesis, transpiration, and stomatal conductance.