水分胁迫对茅苍术根茎生长及挥发油含量的影响

通过控制茅苍术[Atractylodes lancea（Thunb．）DC．]不同生长期的土壤含水量,研究了轻度和重度干旱胁迫与涝渍胁迫对茅苍术根茎生长及挥发油含量的影响。结果表明,在不同生长期,茅苍术根茎生长和挥发油成分含量对不同土壤水分条件的反应不同,其中生殖生长期对水分胁迫较敏感,干旱和涝渍胁迫均会导致根茎生长量和挥发油含量下降。水分胁迫对茅苍术根茎生长量和挥发油含量的影响效应是一致的,导致根茎生长量显著下降的水分条件可使挥发油含量下降,对根茎生长量影响不显著的水分条件则有利于挥发油成分的积累。在果后期进行适当的涝渍胁迫（土壤含水量35．5％～38．5％）有利于茅苍术根茎生长和挥发油含量的提高。     

蛋白核小球藻在光胁迫下的超补偿现象

2000.3-2000.7以蛋白核小球藻(Chlorella pyrenoidosa)为实验材料,测定了其在光胁迫条件下及胁迫解除后细胞的生长密度及生长率。结果表明:光照条件恢复后,遮光处理组较对照组在短期内有更高的产量及生长速率。藻类中存在的这种特性很可能也是形成赤潮爆发的一个生物内源性因素。     

水分胁迫对小麦幼苗及悬浮培养细胞中诱导蛋白表达的影响

丰抗8号小麦幼苗及成熟胚诱导的悬浮培养细胞在水分胁迫（－1．0MPa PEG6000）下,可溶性蛋白含量与蛋白组分变化有差异,幼苗可溶性蛋白含量高于对照,并随生长的延长呈降低趋势;悬浮培养细胞可溶性蛋白含量低于对照,且略有上升;复水后均可恢复对照水平,SDS－PAGE电泳及薄层扫描分析结果表明,幼苗受水分胁迫诱导,出现44．2kD蛋白亚基,该蛋白亚基含量可随胁迫时间延长上升,复水后消失,在正常条件下悬浮培养细胞中含有44．2kD蛋白亚基表达,轻度胁迫处理时,该蛋白亚基含量上升,对悬浮培养细胞进行水分胁迫,该蛋白则表现下降趋势,复水后又可上升。     

施磷和接种AM真菌对玉米耐盐性的影响

在盆栽条件下研究了不同施磷水平（２５,５０,１００,１５０ｍｇ／ｋｇ）,不同盐水平（ＮａＣｌ０,１．２ｇ／ｋｇ）和不同接种ＡＭ真菌处理（接种和不接种）对玉米生长的影响。结果表明,施磷量为５０ｍｇ／ｋｇ时基本满足玉米生长的需要,１．２ｇ／ｋｇ ＮａＣｌ胁迫显著抑制了玉米的生长;施磷明显促进玉米在盐胁迫条件下的生长,施磷水平和接种菌根真菌的交互作用对玉米耐盐性具有显著影响;盐胁迫条件下,接种ＡＭ真菌在     

土壤干旱对沙棘苗木生长及水分利用的影响

研究了土壤干旱条件下盆栽沙棘苗木生长、光合和水分关系的变化。结果表明,同样环境条件下,蒸腾速率随干旱胁迫程度加重而降低,而蒸腾日进程差异不大,均为单峰曲线,峰值出现在11：00;轻、中度干旱胁迫下沙棘叶含水量、水势、渗透势、膨压下降幅度较小,光合速率、侧枝生长速率保持在较高水平,能维持基本的生长量,表现出耐旱植物的生理特征;重度干旱胁迫使上述指标下降较显著,且长时间胁迫后,33．3％沙棘幼苗死亡。     

土壤涝渍对杨树和柳树苗期生长及生理性状影响的研究

研究了两种杨树无性系（ＮＬ８０１０５、ＮＬ８０３５１）和柳树在土壤涝渍条件下的生长及生理性状．结果表明,在涝渍胁迫下苗木根系数量减少,根系长度缩短,根活力下降;高生长降低;最终生物量明显减小;叶片气孔对涝渍胁迫有较强反应,叶片中硝酸还原酶（ＮＲ）活性也会受到一定影响．柳树与杨树之间存在较大差异,无论从生长还是生理性状看,杨树不如柳树耐涝．     

葡萄糖对干旱胁迫下小麦种子萌发及幼苗生长的调节作用

干旱胁迫会抑制小麦种子的萌发及生长,20%聚乙二醇(PEG-6000)模拟干旱胁迫的同时施以不同浓度的外源葡萄糖处理小麦种子,探讨外源葡萄糖对干旱胁迫下小麦种子萌发及幼苗生长的影响。14 h光照/10 h黑暗的光周期培养条件下,较低浓度的葡萄糖(0.02 mmol/L和0.05 mmol/L)促进了干旱胁迫下小麦种子的萌发及幼苗生长,但较高浓度的葡萄糖(0.1 mmol/L,0.2 mmol/L及0.5 mmol/L)加强了干旱胁迫对小麦种子萌发及幼苗生长的抑制效应;而在黑暗条件下培养,葡萄糖的上述调节作用消失。以上结果说明葡萄糖对干旱胁迫下小麦种子萌发及幼苗生长的调节作用具有浓度效应,并且依赖于光。     

镉胁迫对不同品种小麦幼苗生长和生理特性的影响

以4个小麦品种(豫麦4、扬麦15、宝丰7228和宁麦13)为材料,研究了镉胁迫对水培条件下小麦幼苗生长和抗氧化酶系统的影响.结果表明:镉胁迫条件下植株的生长、叶绿素合成及硝酸还原酶活性明显受到抑制;植株体内与氧化胁迫有关的CAT和POD活性下降,H2O2和MDA含量上升;4个品种在镉处理后生长抑制和氧化胁迫程度上表现不同,显示出对镉耐性的差异,其中扬麦15对镉耐性高于其他3个品种.     

用渗透胁迫鉴定小麦种子萌发期抗旱性的方法分析

本以聚乙二醇(PEG)-6000、甘露醇和蔗糖作为渗透剂模拟水分胁迫,胁迫溶液渗透势范围在-0．25MPa到-1．50MPa,分析适于进行小麦种子水分胁迫萌发试验的条件,以鉴定小麦萌发期的抗旱性。结果表明,蔗糖溶液易诱发霉茵,胚芽不能正常生长。渗透势为-0．25MPa的PEG-6000及-0．50MPa的甘露醇胁迫已经显抑制了胚芽伸长;-0．50MPa的PEG-6000及-1．00MPa的甘露醇显抑制种子萌发,随着胁迫强度增加,种子相对发芽率及胚芽长度减小,主要是因为渗透胁迫降低了种子吸水速度,胚芽的相对含水量和渗透势均低。在渗透势相同的胁迫条件下,PEG-6000对小麦种子萌发各项检测值的抑制作用均大于甘露醇。如果目的是通过鉴定小麦种子在高渗溶液中的萌发情况,评价萌发期的抗旱性。选用-0．50MPa的PEG-6000或-1．00MPa的甘露醇较为理想,若同时考虑降低试验成本,则应首选-0．50MPa的PEG-6000。     

土壤水分胁迫与遮荫对生姜生长特性的影响

水分胁迫使生姜叶片叶绿素含量降低,叶片气孔密度及气孔面积减小,根系活力下降。根系伤流量减少,在相同土壤水分条件下,遮光使叶片叶绿素含量增加。气孔密度减小,叶片上表皮气孔变大,而下表皮气孔变小。根系活力增强,水分胁迫显著影响生姜的生长与产量,但不同水分条件下,光强对生姜生长与产量的影响不同,正常供水条件下,生姜在自然光照条件下生长较好,产量较高;水分胁迫条件下,生姜在遮荫条件下生长较好,产量较高。     

Mechanisms of density dependence in fluctuating vole populations: deducing annual density dependence from seasonal processes

Based on recent advances in time-series analyses of ecological dynamics using statistical and mathematical models, we summarise our recent results on the seasonal processes in the annual population dynamics of the grey-sided vole Clethrionomys rufocanus (Sundevall, 1846) in Hokkaido, Japan, and report additional analyses on annual and seasonal density dependence. Annual direct density dependence was strong in almost all populations. In contrast, delayed density dependence was generally weak, although clear delayed density dependence was detected in some of the studied populations. Although seasonal density dependence was observed both in winter and summer, direct density dependence was much more profound during winter; thus, winter density dependence contributed most to the overall annual direct density dependence. We found no correlation between the seasonal components of annual direct density dependence; however, the corresponding seasonal components for annual delayed density dependence were positively correlated. We conclude that winter conditions influence the strength of annual direct density dependence most profoundly. Moreover, we conclude that direct density dependence during summer and winter may be generated by different mechanisms, whereas delayed density dependence seems to be generated by a common mechanism. Candidate mechanisms are discussed in relation to general knowledge of northern rodent populations and to specific insights provided by earlier studies of grey-sided voles in Hokkaido.     

Modification of the response to high density conditions in the guppy, Poecilia reticulata (Peters)

An examination was made of some of the factors which influence the response to density in the guppy. Water from high density fish was given to fish populations kept at high and low densities. This induced high density behaviour in low density fish by increasing aggression and decreasing courtship. But giving 'fresh' water to high density fish failed to alleviate the response to density. 'High density water' slightly reduced the numbers of young found in low density groups. High density fish kept in the dark had more young than high density groups in the light; and the number of young found was decreased when 'high density water' was given to low density fish. The number of ovarian stages was decreased in the dark in high density and was not overridden by the type of water. Giving 'high density water' to low density fish decreased the number of oocytes stage III, but the interaction between water and 'light' was confounded by the total numbers of ovarian stages. Increasing the 'visual space' of high density fish with mirrors partially decreased aggression and increased courtship and number of young found; but had little affect upon the number of ovarian stages. Decreasing the number of physical contacts by keeping the fish chronically tranquillized reduced the activity of the fish. This reduced the aggression of the high density fish and also reduced the differences between the high and low density fish on the basis of their courtship scores, number of young found and number of stages in the ovary. Fish from differing population sizes were given a choice between varying fish densities. The fish from a 'normal' sized population and with an extended visual field, tended to make a choice conforming to the overall selections compared with fish from populations of extreme size and with a reduced visual field.     

Density-dependent growth and reproduction of the apple snail, Pomacea canaliculata: a density manipulation experiment in a paddy field

To examine density dependence in the survival, growth, and reproduction of Pomacea canaliculata, we conducted an experiment in which snail densities were manipulated in a paddy field. We released paint-marked snails of 15–20 mm shell height into 12 enclosures (pens) of 16 m² at one of five densities – 8, 16, 32, 64, or 128 snails per pen. The survival rate of released snails was 95% and was independent of snail density. The snail density had a significant effect on the growth and egg production of individual snails. This density dependence may have been caused by reduced food availability. The females at high density deposited fewer and smaller egg masses than those at low density, and consequently produced fewer eggs. The females at densities 8 and 16 deposited more than 3000 eggs per female, while the females at density 128 oviposited only 414 eggs. The total egg production per pen was, however, higher at higher snail density. The survival rates of juvenile snails were 21%–37% and were independent of adult density. The juvenile density was positively correlated with the total egg production per pen and hence was higher at higher adult density. However, the density of juveniles larger than 5 mm in shell height, i.e., juveniles that can survive an overwintering period, was not significantly different among density treatments. These results suggest that snail density after the overwintering period is independent of the density in the previous year. Thus, density dependence in growth and reproduction might regulate the population of P. canaliculata in paddies. Received: October 23, 1998 / Accepted: July 16, 1999     

Regulation of damseifly populations: the effects of larval density on larval urvival, development rate and size in the field

SUMMARY. 1. The popuhttion density of Coenagrion pttella larvae was monitored in five populations, and of Ischntira elegans in two populations, between October 1982 and May 1983.
2. There was no measurable mortality of larvae over winter and no larval growth until April. Larvae in high density populations were smaller than those in low density populations and were more likely to have a semi- voltine life history.
3. The population density of C. ptiella was also monitored (more frequently) in two populations with differenl initial densities between July and November 1983. In the high density population there was a constant rate of larval mortality, while in the low density population there was no detectable larval mortality, indicating that larval mortality may be density dependent. Larvae in the high density population were again smaller, and more likely to be semi-voitine, than those in the low density population.
4. The role of density dependent larval growth, development and mortality in the regulation of damseifly populations is discussed.     

气候变暖背景下杉木年轮密度对气候因子的响应

为探讨杉木年轮密度与气候因子的响应关系,采用树木年轮学方法,以60年生杉木种源林为研究对象,测定杉木整轮密度、早材密度、晚材密度、晚材最大密度和早材最小密度,分析在气候变暖条件下主要气候因子（温度、降水、相对湿度）对杉木年轮密度及其生长的影响。结果表明：杉木不同年轮密度指标均受到温度、降水和相对湿度的显著影响。早材密度与当年夏季最高温度、当年5月降水量,最大密度与当年10月、当年秋季降水量,最小密度与前一年秋季降水量、最小相对湿度呈显著负相关。滑动相关分析表明气候因子在短时间尺度上对杉木生长影响的稳定性有显著影响,其中杉木年轮最大密度与当年10月、秋季的平均相对湿度和最小相对湿度,最小密度与当年2、3月的平均相对湿度和前一年秋季的平均相对湿度、最小相对湿度、降水量的负相关关系最为稳定。杉木年轮最小密度对前一年气候要素的响应存在滞后效应,且晚材密度对当年春季的气候要素响应也存在滞后效应。研究结果对开展亚热带针叶树种年轮生态学和年轮气候学研究具有重要参考价值,建议选择武夷山的天然林获取更长年表用于重建古气候。     

郭岩山不同海拔丝栗栲细根功能性状及其与土壤因子的关系

为揭示丝栗栲(Castanopsis fargesii)细根功能性状对环境变化的适应机制,对郭岩山500、700、900 m海拔处丝栗栲细根功能性状及其与土壤因子的关系进行研究。结果表明,丝栗栲细根生物量与细根根长密度、表面积密度、组织密度及体积密度呈正相关,细根根长密度、体积密度、表面积密度和比根长4个性状间均呈极显著正相关关系,且均与细根组织密度呈显著负相关。根际土含水量、C和N含量与细根比根长、根长密度、体积密度、表面积密度均存在显著正相关关系,而土壤容重与细根组织密度呈正相关。海拔700 m的细根生物量、根长密度、表面积密度及体积密度显著大于海拔500和900 m的。500和900 m海拔的根长密度、表面积密度与土壤深度呈负相关,而500 m海拔细根的组织密度与土壤深度呈正相关。因此,郭岩山丝栗栲通过改变细根功能性状来适应海拔和土壤的变化。     

Only multimeric hensin located in the extracellular matrix can induce apical endocytosis and reverse the polarity of intercalated cells.

When an intercalated epithelial cell line was seeded at low density and allowed to reach confluence, it located the anion exchanger band 3 in the apical membrane and an H+-ATPase in the basolateral membrane. The same clonal cells seeded at high density targeted these proteins to the reverse location. Furthermore, high density cells had vigorous apical endocytosis, and low density cells had none. The extracellular matrix of high density cells was capable of inducing apical endocytosis and relocation of band 3 to the basolateral membrane in low density cells. A 230-kDa extracellular matrix (ECM) protein termed hensin, when purified to near-homogeneity, was able to reverse the phenotype of the low density cells. Antibodies to hensin prevented this effect, indicating that hensin is necessary for conversion of polarity. We show here that hensin was synthesized by both low density and high density cells. Whereas both phenotypes secreted soluble hensin into their media, only high density cells localized it in their ECM. Analysis of soluble hensin by sucrose density gradients showed that low density cells secreted monomeric hensin, and high density cells secreted higher order multimers. When 35S-labeled monomeric hensin was added to high density cells, they induced its aggregation suggesting that the multimerization was catalyzed by surface events in the high density cells. Soluble monomeric or multimeric hensin did not induce apical endocytosis in low density cells, whereas the more polymerized hensin isolated from insoluble ECM readily induced it. These multimers could be disaggregated by sulfhydryl reagents and by dimethylmaleic anhydride, and treatment of high density ECM by these reagents prevented the induction of endocytosis. These results demonstrate that hensin, like several ECM proteins, needs to be precipitated in the ECM to be functional.     

幼虫密度对草地螟生长发育及繁殖的影响

为了明确幼虫密度对草地螟Loxostege sticticalis种群增长的影响, 对室内条件下（温度22±1℃, RH 70%±5%, 光周期16L∶ 8D）不同幼虫密度[1, 10, 20, 30和40头/瓶（650 mL）］饲养的草地螟生长发育及繁殖进行了研究。结果表明: 幼虫密度对草地螟幼虫体色、 发育历期和存活率, 以及蛹重和成虫生殖等有显著影响。随着幼虫密度的增加, 幼虫体色黑化程度呈增强趋势, 幼虫密度大于10头/瓶时的体色黑化值均显著大于幼虫密度为1头/瓶时的体色黑化值（P<0.05）。20头/瓶的幼虫和蛹历期最短, 且随幼虫密度的增加而显著延长（P<0.05）。幼虫存活率以10头/瓶最高, 其他幼虫密度的幼虫存活率显著较低（P<0.05）。蛹重以1头/瓶的最重, 并随幼虫密度增加而显著下降（P<0.05）。成虫产卵量和交配率分别以1和20头/瓶的幼虫密度最高, 幼虫密度升高则产卵量、 交配率逐渐降低。成虫产卵历期随着幼虫密度的增加逐渐缩短。雌、 雄蛾寿命分别以10和20头/瓶幼虫密度时最长, 幼虫密度过高时雌雄蛾寿命又显著缩短（P<0.05）。生命表分析表明, 幼虫密度对草地螟种群增长指数有显著影响, 以10头/瓶幼虫密度的种群增长指数最高, 幼虫密度过高或过低时种群增长指数下降。据此认为, 幼虫密度是影响草地螟种群增长的重要因子之一。     

Serum lipoproteins of normal and cholesterol-fed rats

The density distribution of lipoproteins in rats fed chow or chow containing 1% cholesterol and 10% olive oil was studied. Lipoprotein fractions were prepared in the ultra-centrifuge between narrow density bands within the density range of 1.006-1.21 and were analyzed by chemical, electrophoretic, and immunological methods. In serum from normal rats there were three major lipoprotein fractions, with densities less than 1.006, 1.030-1.063, and 1.063-1.21. Almost no lipoprotein was found between d 1.006 and 1.030. Most of the low density lipoprotein appeared between a density of 1.04 and 1.05. In the density range 1.05-1.07, small amounts of both low density and high density lipoprotein were found. Feeding a diet high in cholesterol resulted in a marked increase in the concentration of lipoproteins of density less than 1.006, and a new lipoprotein fraction appeared between d 1.006 and 1.030; this fraction contained immunologically demonstrable low density and high density lipoproteins. In addition, there was a decrease in the high density lipoprotein fraction between d 1.070 and 1.21.     

Real mineral density of the sternum

Mineral density of the sternum is insufficiently known. The aim of this research was to investigate mineralisation of the sternum and collect normative data on mineral density of the standard male and female sternum in elderly people (average age of female samples was 64 and male's was 62 years). The research was conducted on 93 cadaveric sternums, 56 male and 37 female samples. To determine regional mineral density of the sternum each sample was cut into six bony segments (Figure 1). Mineral density of every segment was determined using the method of ashing. Male sternums were on average denser than female ones in all segments. Average mineral density of the manubrium in women was 0.169 g/cm3 and 0.220 g/cm3 in men. Average mineral density of the body of the sternum also showed existence of sex difference; it was 0.160 g/cm3 in women and 0.227 g/cm3 in men. Both male and female sternums showed identical mineral density distribution. Mineral density of the manubrium and the body was roughly equal, while the analysis of longitudinal segments showed that the central part of both the manubrium and the body of the sternum was denser than lateral parts. Complex determination of the real mineral density for defined segments of the sternum and analysis of the obtained results were used to create the map of mineral density of the sternum in men and women (Figure 2). Maximum density values were four times greater than minimum density values for analysed samples. These data showed that osteoporosis also occurs on the sternum. Loss of structure and lower mineral density decrease the sternum quality and increase the risk of sternal dehiscence after median sternotomy.