Biological Properties,Trunk Anatomy and Growth Patterns of Cycas panzhihuaensis

Cycas panzhihuaensis L. Zhou et S. Y. Yang is a rare and endangered Cycad that grows in dry-hot valley of Jinsha River. The biological properties, trunk anatomy and growth patterns were studied by field investigation and location observation. The results showed as follows: The sex ratio of cones was strongly male based on reproductive episode. There were no significant sexual differences in leaf number, leaf size, trunk size and ramet number. More than 70% of the adult plants produce ramets, with a mean number of ramets per adult plant of about 2.8. The proportion of individuals with ramets and the number of ramets was positively correlated with trunk height. Maximum mean trunk diameter and mean number of leaves were reached when the plant reached 30--40 cm tall. Further increase of leaf width ceased when the plant reached 5 years old. Leaf reached its maximum length when the trunk was 10 cm tall. Growth units of trunk showed a linear relationship with height. The estimated age could be obtained by counting growth units of the trunk. The survival curve of leaves was well described by Deevey type Ⅰ . The survival time of many leaves was two growth units. The rate of leaf mortality abruptly increased after two growth units. Few leaves could survive five units.     

The Late Triassic Araucarioxylon Arizonicum trees of the Petrified Forest National Park, Arizona, USA

Examination and measurement of many of the trunks attributed to Araucarioxylon arizonicum Knowlton eroded from the Late Triassic Chinle Formation in the Petrified Forest National Park, Arizona demonstrate that the living tree did not closely resemble any of the present-day Araucaria trees of the southern hemisphere as postulated in past reconstructions. The research indicates that it was a tall monopodial tree with branches occurring in a disordered manner on the trunk from the base to the crown. Calculations using the allometric method of Niklas indicate that the trees were of considerable size. The largest recorded trunk has a basal diameter of nearly 3 m and may represent a tree 59 m high, when living. The root system of the A. arizonicum tree consisted of a ring of four to six steeply inclined lateral roots and a massive, vertically directed tap root. Many of the trunks still have their root systems attached, a circumstance that indicates their felling by the cut-bank operations of the local river system. The massive roots of these trunks, particularly the large tap root, are consistent with growth in soft, deep, alluvial soil, and the thin scale bark is to be expected in a tropical climate free from frost.     

Comparative hydraulic and anatomic properties in palm trees (Washingtonia robusta) of varying heights: implications for hydraulic limitation to increased height growth

As trees grow taller, the energetic cost of moving water to the leaves becomes higher and could begin to limit carbon gain and subsequent growth. The hydraulic limitation hypothesis states that as trees grow taller, the path length and therefore frictional resistance of water flow increases, leading to stomatal closure, reduced photosynthesis and decreased height growth in tall trees. Although this hypothesis is supported by the physical laws governing water movement in trees, its validation has been complicated by the complex structure of most tree species. Therefore, this study tested the hydraulic limitation hypothesis in Washingtonia robusta (H. Wendl.), a palm that, while growing to tall heights, is still structurally simple enough to act as a model organism for testing. There were no discernable relationships between tree height and stomatal conductance, stomatal densities, guard cell lengths, leaf dry mass per unit area (LMA) or sap flux, suggesting that these key aspects of hydraulic limitation are not reduced in taller palms. Taller palms did, however, have higher maximum daily photosynthetic assimilation rates, lower minimum leaf water potentials that occurred earlier in the day and fewer, smaller leaves than did shorter palms. Leaf epidermal cells were also smaller in taller palms compared with shorter ones. These findings are consistent with hydraulic compensation in that tall palms may be overcoming the increased path length resistance through smaller, more efficient leaves and lower leaf water potentials than shorter palms.     

How the timberline formed: altitudinal changes in stand structure and dynamics around the timberline in central Japan

Background and Aims

Altitudinal timberlines are thought to move upward by global warming, a crucial topic in ecology. Tall tree species (the conifer Abies mariesii and the deciduous broad-leaved Betula ermanii) dominate the sub-alpine zone between 1600 and 2500 m a.s.l., the timberline, on Mount Norikura in central Japan. Dwarf pine Pinus pumila dominates above the timberline to near the summit (3026 m a.s.l.). This study evaluated how the timberline formed on Mount Norikura by examining altitudinal changes in stand structure and dynamics around the timberline.

Methods

One hundred and twenty-five plots of 10 m × 10 m were established around the timberline (2350–2600 m a.s.l.). Trunk diameter growth rate during 6 years was examined for A. mariesii, B. ermanii and P. pumila. Mortality during this period and mechanical damage scars on the trunks and branches due to strong wind and snow were examined for A. mariesii only.

Key Results

The density, maximum trunk height and diameter of A. mariesii in plots decreased with altitude. The maximum trunk height of B. ermanii decreased with altitude, but density and maximum trunk diameter did not decrease. In contrast, the density of P. pumila abruptly increased from around the timberline. A strong negative correlation was found between the densities of P. pumila and tall tree species, indicating their interspecific competition. Trunk diameter growth rates of A. mariesii and B. ermanii did not decrease with altitude, suggesting that these two tall tree species can grow at the timberline. The ratio of trees with mechanical damage scars increased with altitude for A. mariesii, a tendency more conspicuous for larger trees. The mortality of larger A. mariesii was also greater at higher altitude. Tall tree species may not increase their trunk height and survive around the timberline because of mechanical damage.

Conclusions

This study suggests that the altitudinal location of the timberline is mainly affected by mechanical damage due to strong wind and snow rather than by growth limitation due to low temperature. Therefore, the timberline would not move upward even under global warming if these growth and mortality characteristics do not change for a long time.     

Influence of Temperature on Nitrate Metabolism and Leaf Expansion in Soybean (Glycine max L. Merr.) Seedlings

The effect of various day temperatures on NADH-nitrate reductase, NADH- and NADPH-glutamate dehydrogenases, nitrate, protein and leaf area, measured at intervals during the ontogeny of the first trifoliolate soybean leaf, was determined. At 32.5 C and 25 C, nitrate concentration, nitrate reductase, and NADPH-glutamate dehydrogenase activities increased concurrently with leaf development and then decreased as leaf maturation progressed. At 40 C, these three components showed no initial increase and the concentration or activities decreased throughout the development of the leaf. The effects of temperature on NADH-glutamate dehydrogenase were the reverse. Rates of protein accumulation were higher at 40 C during the first 2 days of leaf development while higher rates were measured the first 5 days of leaf growth at 32.5 C. At 25 C, protein accumulation was low during the first 3 days of leaf growth, increased in the period of 3 to 5 days, and then declined up to 8 days of leaf development. Leaf expansion progressed at faster rates at 32.5 C and 25 C and at a much slower rate at 40 C. Leaf growth was essentially complete after the fifth day regardless of temperature.     

PRICKLE DISTRIBUTION IN ARALIA SPINOSA (ARALIACEAE)

The density of Aralia spinosa prickles varied with the age and architectural position of annual increments. Prickles were most common on young (1–4 years old, 2–3 m tall), unbranched stems. Prickles were less common on branches and were absent on inflorescences. Ramets that grew as sprouts after injury had more and longer prickles than ramets that had not arisen in this way. Leaf prickles were also more common on the leaves of trunk annual increments than on the leaves of branch annual increments. As with stem prickles, leaf prickles were more common on the leaves of stems that had sprouted after cutting than on the leaves of ramets that had not been previously cut. As bark developed, stem prickles were lost at a rate of about 10% per year. While dense prickles characterized young individuals, older individuals (>15 years old) had very few prickles.     

民勤绿洲荒漠过渡带梭梭东、西方位树干液流特征及相关性分析

采用Grainer热扩散式探针法( TDP )连续测定了6月份至11月份民勤绿洲荒漠过渡带梭梭﹝Haloxylon ammodendron ( C. A. Mey.) Bunge﹞东、西方位的树干液流速率,并同步测定了相关环境因子;在此基础上,对晴天、阴天和雨天东、西方位树干液流速率的日变化以及实验期间东、西方位树干液流速率和各环境因子的变化进行了分析,并对不同天气和时间尺度东、西方位树干液流速率间的相关性及其与部分环境因子的相关性进行了分析。结果表明：在生长旺盛期(6月份至8月份),晴天时梭梭东、西方位树干液流速率的日变化均表现为明显的“宽峰型”曲线;在整个观测期内,不同天气的树干液流速率存在一定差异,东、西方位的树干液流速率也存在一定差异,并且其差异在夜间较白天更明显;总体来看,东方位的树干液流速率高于西方位。相关性分析结果表明：不同天气和时间尺度东、西方位的树干液流速率间存在极显著正相关性,其相关系数均在0.90以上并略有差异。总体来看,晴天梭梭东、西方位树干液流速率间的相关性高于阴天和雨天,并且,日尺度东、西方位树干液流速率间的相关性最强。晴天东、西方位树干液流速率与各环境因子的相关性高于阴天和雨天,并且,小时尺度东、西方位树干液流速率与环境因子间的相关性高于日尺度。西方位树干液流速率与环境因子的相关性略高于东方位,说明西方位的树干液流速率对环境因子变化的反应更敏感。晴天和阴天东、西方位树干液流速率与参考作物蒸散量( ET0)的相关性极显著,其相关系数均在0.70以上,说明根据梭梭东、西方位树干液流速率计算其耗水量具有一定的可行性。研究结果显示：梭梭树干液流速率与天气、环境因子、时间尺度和树干方位等均有一定关系。     

Significance of leaf orientation for leaf temperature in an amazonian sclerophyll vegetation

Summary The influence of leaf orientation on leaf temperature has been studied in an sclerophyll vegetation of the Amazon basin, which grows on white sandy soils of very low water retention capacity and variable depth of the water table.Leaf size of the species studied is mainly mesophyllous (sensu Raunkiaer). The high degree of leaf inclination in all species is very characteristic; 55% of the leaves present inclination angles (relative to the vertical) smaller than 45°.Water potential is generally high, not being lower than –14 bars. Leaf resistance increases toward noon during the course of sunny days, indicating either water stress at leaf level or the influence of low relative humidity on stomata opening.Leaf temperature under sunny conditions reflects the influence of leaf orientation on the amount of radiation absorbed by the leaf. Temperature differences recorded range from 1.8–5.4° C. The difference depends on leaf angle, leaf color and leaf diffusion resistance during the period of measurement.Analysis of the relationship between leaf angle and leaf temperature, using Gates leaf energy balance, shows that under the conditions prevailing at noon in sunny days, leaf angles smaller than 50° are effective in reducing leaf temperature within a wide range of leaf resistances to water vapor transfer.Contribution from the Venezuela MAB-1 Programm, partially supported by the National Research Council (CONICIT) and the Organization of American States (OEA)     

BACTERIAL CANKER OF STONE-FRUITS III. INOCULUM CONCENTRATION AND TIME OF INOCULATION IN RELATION TO LEAF-SCAR INFECTION OF CHERRY

Leaf scars on the fruiting spurs of the cherry varieties Roundel (high resistance) and Napoleon (low resistance) were inoculated with Pseudomonas mors-prunorum on four separate occasions in the autumn, using, on each occasion, the same range of five different inoculum concentrations. The results, recorded the following year, showed that the percentage diseased spurs (disease incidence) and the severity of the disease symptoms (disease severity) both increased with inoculum concentration.
The median threshold concentration of inoculum (T. C. 50), defined as the concentration necessary to give 50% diseased spurs, varied with time of inoculation, but on all occasions was considerably higher for Roundel than for Napoleon.
In another experiment the leaf scars at the nodes of the current year's growth, inoculated at weekly intervals throughout the autumn, were found to be susceptible from the beginning of September to the latter part of October. During this period disease incidence varied considerably with time of inoculation. There was evidence that this variation was related to two factors which influenced the numbers of bacteria penetrating into leaf scars, namely, (1) the rate of evaporation of the infection drop, and (2) the rate of suction of inoculum into the vessels of the leaf traces.
The experiments provided evidence of a long infection period beginning early in the autumn. It is suggested, therefore, that the timing of bactericidal sprays in the autumn be advanced and that the present concept of 'protective' sprays in disease control be replaced by one based on the eradication of external sources of inoculum.     

The identification of growth stages in winter wheat with reference to the application of growth-regulator herbicides

The development of several varieties of winter wheat {Triticum aestivum) in early spring was studied in order to relate the progress of apical differentiation to easily measured external characters and so provide a guide to the correct timing of herbicide applications. Leaf sheath lengths were more closely related to apical development than were tiller or leaf numbers. Spikelet differentiation occurred when the longest sheaths were c. 5 cm tall. Application of a growth regulator herbicide before this stage of development caused ear deformities in the crop at harvest. A measure of leaf sheath length might, therefore, replace the ambiguous criteria presently used to judge the stages of winter wheat most tolerant of herbicides.     

Carbon/Nitrogen Imbalance Associated with Drought-Induced Leaf Senescence in Sorghum bicolor

Drought stress triggers mature leaf senescence, which supports plant survival and remobilization of nutrients; yet leaf senescence also critically decreases post-drought crop yield. Drought generally results in carbon/nitrogen imbalance, which is reflected in the increased carbon:nitrogen (C:N) ratio in mature leaves, and which has been shown to be involved in inducing leaf senescence under normal growth conditions. Yet the involvement of the carbon/nitrogen balance in regulation of drought-induced leaf senescence is unclear. To investigate the role of carbon/nitrogen balance in drought-induced senescence, sorghum seedlings were subjected to a gradual soil drought treatment. Leaf senescence symptoms and the C:N ratio, which was indicated by the ratio of non-structural carbohydrate to total N content, were monitored during drought progression. In this study, leaf senescence developed about 12 days after the start of drought treatment, as indicated by various senescence symptoms including decreasing photosynthesis, photosystem II photochemistry efficiency (Fv/Fm) and chlorophyll content, and by the differential expression of senescence marker genes. The C:N ratio was significantly enhanced 10 to 12 days into drought treatment. Leaf senescence occurred in the older (lower) leaves, which had higher C:N ratios, but not in the younger (upper) leaves, which had lower C:N ratios. In addition, a detached leaf assay was conducted to investigate the effect of carbon/nitrogen availability on drought-induced senescence. Exogenous application of excess sugar combined with limited nitrogen promoted drought-induced leaf senescence. Thus our results suggest that the carbon/nitrogen balance may be involved in the regulation of drought-induced leaf senescence.     

Assessment of spatial distribution of growth in the elongation zone of grass leaf blades

Knowledge about the spatial distribution of growth is essential for understanding the leaf growth process. In grasses the elongation zone is located at the base of the leaf blade and is enclosed by sheaths of older leaves. Assessment of spatial growth distribution, therefore, necessitates use of a destructive method. We used a fine needle to make holes through bases of tillers at the location of the leaf elongation zone of tall fescue (Festuca arundinacea Schreb.), then measured the displacement of the holes after a 6 or 24 h interval. Needle holes caused a 22 to 41% decrease in daily leaf elongation so experiments were conducted to investigate if the spatial distribution of growth in the elongation zone was altered. Leaf elongation rate was reduced similarly when needle holes were made within or above the zone where cell elongation occurs. Distribution of elongation within the zone was the same when estimated by displacement of needle holes or ink marks placed on the epidermis of the elongation zone after surrounding tissue had been removed. Making holes at different locations within the elongation zone did not differentially affect the relative contribution of the damaged or undamaged parts to leaf elongation. These findings demonstrate that needle holes or ink marks in paired leaves can be used to estimate the relative distribution of growth in the elongation zone of undamaged tall fescue leaf blades.     

干旱区植物叶片大小对叶表面蒸腾及叶温的影响

利用热及物质交换原理, 并结合前人研究成果, 在单叶尺度上建立了简单的叶温和水气蒸腾模型。模型通过预设值驱动, 预设值参照干旱区环境及植物叶片特征设置。模拟结果显示: 随气孔阻力的增加, 叶片蒸腾速率降低, 叶温升高; 同一环境下, 具有低辐射吸收率的叶片蒸腾速率和叶温更低, 并且气孔阻力越大, 这种差异越明显。另外, 叶片宽度及风速是影响叶片蒸腾及叶温的重要因子。干旱地区植物生长季节, 风速小于0.1 m·s ^-1、气孔阻力接近1000 s·m ^-1时, 降低叶片宽度不仅有利于降低叶片温度, 而且能够降低叶片蒸腾速率, 从而实现保持水分, 增强植物适应高温、干旱的能力。     

Regulation of leaf growth of grass by blue light

Changes in light quality occur naturally within a canopy when a plant grows from unshaded to shaded conditions, and the reverse occurs after a cut that reduces shading. These changes in light quality could be responsible for the variation in leaf elongation and appearance rates of grasses. The role of blue light in leaf growth was investigated in tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.). Leaf length was measured daily following a decrease or an increase in blue light to evaluate effects on duration of leaf growth, leaf elongation and the rate of leaf appearance rate. A reduction in blue light increased sheath length by 8 to 14% and lamina length by 6 to 12% for both species. These increases could be reversed by enrichment of blue light. With low blue light treatment, final leaf length was increased due to a greater leaf elongation rate. In tall fescue, but not in perennial ryegrass, this effect was coupled with a greater phyllochron and a longer duration of leaf elongation. Development of successive leaves on a tall fescue tiller were co-ordinated. A decrease in blue light increased the duration of elongation in the oldest growing leaf and also delayed the appearance of a new leaf, maintaining this co-ordination. We conclude that final leaf size and phyllochron for tall fescue can be significantly modified by blue light. Perennial ryegrass appeared less responsive, except for displaying longer sheaths and laminae in low blue light, as also occurred for tall fescue. We hypothesize that leaf length could be regulated by the quality of the light reaching the growing region itself.     

星天牛在悬铃木木段上的产卵行为研究

为明确产卵木段粗细对星天牛Anoplophora chinensis刻槽产卵的影响、了解刻槽产卵习性及产卵规律,以不同直径悬铃木Platanus acerifolia木段为产卵材料,通过无选择和选择性产卵试验,测定了星天牛在悬铃木上产卵部位选择,并监测了星天牛的产卵过程。结果表明：星天牛产卵过程主要包括刻槽部位选择、咬槽、产卵和封槽4个阶段。星天牛在不同直径的悬铃木木段上都能刻槽产卵,但木段的粗细对刻槽数量、产卵量的影响差异显著,对空槽率、卵的大小没有影响。刻槽产卵行为主要集中在直径10~15 cm木段。在直径3~5 cm木段上刻槽数量和产卵量最低,显著低于直径大于5 cm的木段。在武汉地区,星天牛产卵高峰期在6月下旬-7月中旬,孵化高峰期在7月中下旬。该结果为深入研究星天牛的生殖行为,精准监测和防控提供参考。     

Characterization of Growth-Retardant Effects on Vegetative Growth of Date Palm Seedlings

The leaves, inflorescences, and fruit bunches of date palm trees develop at the crown, which is the apex of a single trunk that can be up to 25 m tall. Because palm trees are monocots, the leaves and inflorescences are generated deep within the trunk from a single meristem—the palm heart—and are inaccessible for direct bioregulator treatments. We followed the effects of two growth regulators, paclobutrazol and uniconazole-P, on the vegetative growth of young date palm seedlings. Both growth regulators constrained the elongation rate of the leaves and reduced the leaf length. Microscopic analysis of dissected palm hearts revealed that the growth retardants did not affect the generation of new leaves. However, the treatments did change the dimensions of the developing embryonic leaves as well as the shape of the apical meristem. The results suggest the possible future use of growth retardants to reduce trunk height, enabling cheaper, safer, and more efficient management of date palm trees.     

How does the richness of wood-decaying fungi relate to wood microclimate?

Microclimatic conditions in dead wood influence fungal growth and hence also species composition, but it remains unclear how they influence species richness in nature. We analysed fungal species richness based on the occurrence of fruit bodies on 2 m long segments of both standing and lying trunks of Norway spruce (Picea abies). The number of non-red-listed species was related positively to moisture, and negatively to both temperature extremes and fluctuations. The numbers of both red-listed and non-red-listed species were further differently influenced by trunk diameter and by trunk properties related to the progression in wood decay. These results indicate that the richness of fungal communities in dead wood is shaped by an interaction of wood decay, moisture and temperature fluctuations.     

Responses of crown development to canopy openings by saplings of eight tropical submontane forest tree species in Indonesia: a comparison with cool-temperate trees

BACKGROUND AND AIMS: Growth in trunk height in canopy openings is important for saplings. How saplings increase height growth in canopy openings may relate to crown architectural constraints. Responses of crown development to canopy openings in relation to trunk height growth were studied for saplings (0.2-2.5 m tall) of eight tropical submontane forest tree species in Indonesia. The results of this study were also compared with those of temperate trees in northern Japan. METHODS: The crown architecture differed among the eight tropical species, i.e. they had sparsely to highly developed branching structures. Crown allometry was compared among the eight species in each canopy condition (closed canopy or canopy openings), and between closed canopy and canopy openings within a species. A general linear regression model was used to analyse how each species increases height growth rate in canopy openings. Crown allometry and its plasticity were compared between tropical and temperate trees by a nested analysis of covariance. KEY RESULTS: Tropical submontane trees had responses similar to cool-temperate trees, showing an increase in height in canopy openings, i.e. taller saplings of sparsely branched species increase height growth rates by increasing the sapling leaf area. Cool-temperate trees have a wider crown projection area and a smaller leaf area per crown projection area to avoid self-shading within a crown compared with tropical submontane trees. Plasticity of the crown projection area is greater in cool-temperate trees than in tropical submontane trees, probably because of the difference in leaf longevity. CONCLUSIONS: This study concluded that interspecific variation in the responses of crown development to canopy openings in regard to increasing height related to the species' branching structure, and that different life-forms, such as evergreen and deciduous trees, had different crown allometry and plasticity.     

Fructan Content and Synthesis in Leaf Tissues of Festuca arundinacea

The concentration of fructan in tall fescue (Festuca arundinacea Schreb.) changes during growth and in response to environment. The objective of this research was to compare the fructan concentration and fructosyl-transferase activity of tall fescue leaf tissues. Expanding leaves, inner and outer sheaths, and expanded blades of greenhouse-grown tall fescue plants were assayed for fructan concentration and fructosyl-transferase activity. Leaf sheaths contained significantly more nonstructural carbohydrate than did the expanded blade. Sheaths also contained a greater percentage of fructan with more than six sugar residues (long chain fructan), than either the expanded blade or expanding leaf. Expanding leaves contained a greater concentration of fructose and oligosaccharides than did sheath or blade tissues. Expanding leaves also had the greatest fructosyl-transferase activity measured either as radiolabel incorporated into fructans in tissue pieces or protein extracts. Activity of fructosyl-transferase was greater in expanding leaf tissue than in sheath tissues.