獐牙菜种子萌发的研究

对温度、光照、植物激素（GA₃、NAA）条件对獐牙菜（Swertia bimaculata）种子萌发的影响进行了研究。结果表明,獐牙菜种子萌发的适宜温度为15～20℃,低温贮藏可促进其萌发,而有无光照对獐牙菜种子萌发没有明显影响,GA₃处理可提高其萌发势和萌发率,而NAA处理仅提高其萌发势。研究认为：獐牙菜种子具有休眠现象;激素及低温贮藏对打破种子的休眠具有重要作用。     

刺木蓼和长枝木蓼种子休眠的解除及萌发条件

刺木蓼（Atraphaxis spinosa）和长枝木蓼（A.virgata）为蓼科木蓼属灌木,是乌鲁木齐周边植被组成的重要种。这两种木蓼种子成熟后不萌发,处于休眠状态,对其种子进行5℃（黑暗）和野外低温层积处理,结果表明：5℃层积处理能明显提高两种木蓼种子在15/6、20/10、25/15和30/20℃（昼12 h/夜12 h）的萌发率。野外层积处理显著提高了种子在15/6℃的萌发率。刺木蓼和长枝木蓼的种子均为非深度生理休眠,分别经8、6周的低温层积处理后种子休眠得以解除。刺木蓼种子的休眠程度比长枝木蓼深,休眠解除后,种子萌发所需的最低温度降低。这两种木蓼种子经过冬天的低温层积,可以在春天较低的生境温度下萌发。     

南方鲇幼鱼的热耐受特征

为了研究不同驯化温度对南方鲇（Silurus meridionalis Chen）幼鱼热耐受性特征的影响,在水温为10 ℃、20 ℃和30 ℃的条件下,对南方鲇幼鱼（（16.9±0.3）g）进行2周的驯化,以1 ℃·h^-1的变温速率连续观测实验鱼的耐受温度,各驯化温度下的最大临界温度（CT_max）、最大致死温度（LT_max）、最小临界温度（CT_min）和最小致死温度(LT_min）分别为3413 ℃、3822 ℃、39.41 ℃;34.84 ℃、38.63 ℃、39.53 ℃;4.88 ℃、5.90 ℃、9.80 ℃;4.12 ℃、5.03 ℃、8.29 ℃。结果表明：最大临界温度和最大致死温度随驯化温度的升高而增大,最小临界温度和最小致死温度随驯化温度的降低而减小;经计算,南方鲇幼鱼在各驯化温度下的温度耐受幅分别为29.25 ℃、32.32 ℃和29.61 ℃;在10 ℃～20 ℃的驯化温度范围内高、低温驯化反应率分别为0.41和0.12,而在20 ℃～30 ℃驯化温度范围内高、低温驯化反应率分别为0.10和0.39;热耐受区域面积为617.5 ℃²;证明南方鲇幼鱼的热耐受性明显有赖于驯化温度。     

）种群结构与动态

为了阐明秦岭巴山冷杉（Abies fargesii）种群的结构特征和动态规律,对位于秦岭中段南坡佛坪保护区内不同海拔分布的巴山冷杉种群的年龄结构、生命表以及存活曲线等进行了研究。结果表明: 在海拔2350、2500和2700 m,巴山冷杉种群都表现为衰退型,种群个体主要聚集在中龄级,幼龄级的个体都极度缺乏。在各海拔巴山冷杉种群生命表中,死亡量（d_x）、死亡率（q_x）和消失率（K_x）都为负值,反映了种群幼龄个体的缺乏程度。随着海拔的升高,幼龄级个体数量增加而大龄级个体数量减少。巴山冷杉种群生命表和存活曲线的分析表明,巴山冷杉种群个体存活量最多的年龄级和出现最大死亡率的年龄级都随着海拔的降低而依次后推。随着海拔的升高,巴山冷杉种群的分布格局由随机分布类型过渡为聚集分布类型。     

水分胁迫对云杉光合特性的影响

比较研究了3年生红皮云杉和嫩江云杉苗木在不同水分条件下的光合特征,并探讨其对水分胁迫的适应机制。研究结果表明,不同光强下两种云杉的最大光合速率（P_max）随土壤含水量的降低而逐渐下降,且嫩江云杉的降幅较小;表观量子效率（AQY）、蒸腾速率（Tr）、气孔导度（G_s）也都呈下降的趋势。暗呼吸速率（R_d）和水分利用率（WUE）在逐渐干旱的过程中先上升后下降,而胞间CO₂浓度先下降,后随上升。这表明在水分胁迫较为严重时,光合速率的降低主要是非气孔限制造成的。比较上述指标的变化情况可以看出,嫩江云杉对干旱的适应性要强于红皮云杉。     

光照和温度对望天树种子萌发的影响

在实验室内人工气候箱控制的条件下,研究了我国重要珍稀濒危植物望天树（Shorea wantianshuea,龙脑香科（Dipterocarpaceae））种子萌发对持续光照、14小时光照／10小时黑暗周期性光照的反应;同时研究了望天树种子的萌发对不同温度的反应和低温贮藏对种子活力的影响。结果表明,不论是持续光照还是周期性光照都不能提高望天树种子的萌发率,相反,持续光照和周期性光照都不同程度降低了种子萌发率。光照能通过加速或延迟种子萌发的进程、或改变幼苗活力指数和萌发指数而影响种子萌发的质量;持续光照延迟种子萌发的进程,而周期性光照加快种子萌发的进程。30℃是种子的最适萌发温度,虽然15℃和5℃的相对低温对幼苗活力指数影响不大,但大大延迟了种子萌发进程,并提高萌发率。望天树种子不能耐受5℃低温贮藏,但具有在15℃下短期贮藏的潜力和一定程度的生理性休眠。     

开花期加拿大一枝黄花水浸提液对3种作物种子萌发和幼苗生长的影响

测定了入侵杂草加拿大一枝黄花（Solidago canadensis）开花期的茎、叶和花序水浸提液对辣椒(Capsicum annuum)、番茄(Lycoperiscum esculetum)、长梗白菜(Brassica chinensis var. communis)种子萌发和幼苗生长的影响。结果表明：（1）处于开花期的加拿大一枝黄花存在明显的化感作用,在25 mg·mL^-1时,对3种作物种子苗生长有促进作用,浸提液高于50 mg·mL^-1时,作物种子的萌发率和生长受到抑制,这种抑制作用随处理液浓度的提高而增强,在100 mg·mL^-1浓度处理下,甚至使作物种子失去活力;（2）加拿大一枝黄花叶和花序的水浸提液对种子萌发和生长的影响要大于其茎的浸提液;（3）在3种作物中,长梗白菜种子对加拿大一枝黄花水浸提液的敏感性最高。     

武夷山不同海拔高度土壤氮矿化对温度变化的响应

采集了武夷山4个不同海拔的植物群落（常绿阔叶林、针叶林、亚高山矮林和高山草甸）的土壤样品,在实验室条件下, 将含水量调节为田间持水量60%,置于5 ℃、15 ℃、25 ℃和35 ℃人工气候箱中培养30 d,以测定土壤净氮矿化对温度的敏感性。结果表明：相同海拔植物群落的土壤净氮矿化量和氮矿化速率均随温度的升高显著增加;不同海拔间土壤氮矿化量和氮矿化速率大小均表现为：亚高山矮林>常绿阔叶林>高山草甸>针叶林。土壤氮矿化的Q₁₀在1.03～1.54,并且15 ℃升高到25 ℃时的Q₁₀比5 ℃升高到15 ℃和25 ℃升高到35 ℃时的Q₁₀高,表明土壤氮矿化对温度的敏感性在15 ℃～25 ℃较高。     

风箱果种子催芽技术研究

以风箱果自然种群成熟的种子为研究对象,对种子的生活力和催芽方法进行了研究,结果表明：TTC染色法测得风箱果种子的生活力达到94.44%;清水浸种处理的发芽势和发芽率均较低,以浸种48 h的效果较好,发芽率为28.33%;不同化学药剂处理均能不同程度的提高发芽率,其中50 mg·L^-1 GA₃+4%KNO₃的混合药剂处理72 h的萌发效果最好,发芽率达到90%;100和200 mg·L^-1 GA₃能极显著提高发芽势（P<0.01）;低温处理28 d能显著提高发芽势和发芽率（P<0.05）。     

松科植物属间C值和种子千粒重与进化关系初探

在检索C值数据库和种子数据库的基础上,对松科具有完整C值和种子千粒重等数据信息的5个属108种植物进行统计分析,并利用线性回归模型分析了二者之间相关性。结果显示,松科植物C值从9.5~36 pg呈正态分布,种子千粒重从1.2~1 269 g呈偏态分布,种间千粒重相差悬殊,高达1058倍。ANOVA分析表明,松属C值平均为25.79 pg,显著高于其它4个属;落叶松属C值最低（12.53 pg),显著低于云杉属（18.44 pg）,而云杉属、冷杉属和雪松属C值间却无显著性差异。结合前人研究结果,从C值的角度分析,松科5属间的演化顺序为：松属→云杉属→雪松属→冷杉属→落叶松属。松科5属间种子千粒重均值差异显著,松属种子均值最大（123.7 g）,其次为雪松属（84.5 g）和冷杉属（26.4 g）,最后为落叶松属（5.5 g)和云杉属(3.9 g)。除松属外,其它4个属ANOVA分析,雪松属种子千粒重显著高于云杉属、冷杉属和落叶松属（P<0.01),而云杉属和落叶松属种子千粒重间无显著差异(P>0.05)。对数回归分析和线性相关性分析表明,松科108种植物的C值和种子千粒重回归方程为：y=3.145x-7.248,决定系数（R²）为0.346,存在显著正相关性（P<0.000 1）,线性相关系数(γ)高达58.8%,这说明松科植物随着C值增大,其种子千粒重呈明显增加趋势。综上所述,松科属间种子千粒重差异显著,且随着属间进化程度的提高,C值和种子千粒重均呈明显下降趋势,其具体机理尚有待于结合其它功能性状做深入分析。     

Bud formation inHydra: Inhibition by an endogenous morphogen

Summary From crude extracts ofHydra tissue a substance has been purified which prevents or retards the asexual reproduction by budding. The molecular weight is in the range of 300 to 1000 daltons. Inhibition of bud formation can be observed with concentrations equivalent to the extract from one hydra per 4 ml, that is, to a more than 10,000-fold dilution of the initial crude extract of a hydra. The purified inhibitor is active at a concentration of less than 10^–8 M.Most of the inhibitor present inHydra is bound to cells. Within the cells the substance is mainly bound to particulate structures which sediment at 10,000 g. Its concentration is highest in the hypostomal region and decreases in the direction of the tentacles and peduncle. A second, lower, peak has been found in the basal disc. Treatment of the animals with a toxic agent (nitrogen mustard) which depletes the animal of interstitial cells, nematocytes and nematoblasts excludes the possibility that the inhibitor is present to any great extent in these cells. In conjunction with cell separation experiments by centrifugation of fixed cells in suspension, these results indicate that nerve cells are the most likely sites of storage of the inhibiting substance, although epithelial cells are not excluded as sources for the inhibitor.     

Quantitative genetics of bud phenology, frost damage, and winter survival in an F2 family of hybrid poplars

We studied the quantitative genetics of bud phenology, fall frost damage, and winter survival in an F₂ family (no. 822) of Populus hybrids derived from a cross between two full-sub F₁ hybrids (P. trichocarpa (Torr. & Gray×P. deltoides Bartr.). Field traits studied included the timing of bud set (BS_F) in Minnesota and Oregon, the timing of bud flush (BF_F) in Oregon, as well as fall frost damage (FD_F) and winter survival (WS_F) in Minnesota. We conclude that Family 822 has substantial genetic variability for all field traits, BS_F and BF_F are under moderate to strong genetic control (H ² _i =0.48–0.80), FD_F and WS_F are under low to moderate genetic control (H ² _i =0.27–0.40), and late bud set is associated with increased frost damage and decreased winter survival. In a warm greenhouse, we measured the timing of bud set and the number of new leaves on trees growing under either an 8-h photoperiod (BS_SD and NL_SD) or a natural photoperiod (NP) from August to December (BS_NP and NL_NP). We found that BS_SD, NL_SD, and NL_NP are under moderate genetic control (H ² _i =0.53–0.70), but the heritability of BS_NP could not be determined because few trees set bud in the warm greenhouse under the NP. By comparing results from the greenhouse experiments with results from the field, we conclude that the genetic correlation between BS_SD and BS_F (0.53–0.60) is relatively modest and that NPs in the fall are relatively ineffective at promoting bud set under warm greenhouse temperatures, although bud set readily occurred in the field. Although, low levels of light pollution in the greenhouse might have affected BS_NP, results from both greenhouse and field experiments suggest that genetic differences in photoperiodic responses play a modest role in explaining genetic differences in the timing of bud set under natural field conditions. Therefore, genetic differences in responses to other environmental factors, such as temperature, deserve greater attention. Received: 11 November 1999 / Accepted: 24 November 1999     

Critical Roles of a RhoGEF-Anillin Module in Septin Architectural Remodeling during Cytokinesis

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松嫩平原碱化草甸旱地生境芦苇种群的芽流和芽库动态

在松嫩平原碱化草甸,旱地生境芦苇种群的根茎分布在土层约1m的不同深度,一般可生活6个年度,个别根茎可存活7～9年,乃至更长的时间.通过芦苇根茎芽调查,创建了植物种群的芽流模型.提出了采用当年1龄级根茎芽的输入率与其它龄级休眠芽库存率之和估计芦苇种群芽库贮量动态的方法.结果表明,随着生长季的进程,芦苇种群芽库输入率呈不断增加趋势,而萌发输出率呈不断减少的趋势,死亡输出率则大体保持相同的较低水平.至休眠前期的9月底,芽库输入率已为输出率的2.04倍.在松嫩平原碱化草甸旱地生境,芦苇种群各龄级根茎的休眠芽有一个稳定的萌发输出过程.定量分析结果表明,芦苇种群不同龄级根茎的休眠芽每年都有11%的比率萌发形成1龄级新根茎.1龄级根茎顶端翌年发育为分蘖株后,可为直接相连接的老龄级根茎就近输送养分,从而实现老龄级根茎芽的活力.     

Synthèses ďacides nucléiques et de protéines au cours de ľinitiation de bourgeons adventifs sur des explantats de Cichorium intybus cultivés in vitro

Synthesis of nucleic acids and proteins during initiation of vegetative buds from explants of Cichorium intybus cultivated in vitro .
Explants of 6 mm diameter and 2 mm thickness from roots of Cichorium intybus L. (var. WitIoof cv. "Zoom"), grown in vitro in the presence of kinetin (l0_–6 M ), produced only buds. By comparing the histological events and the biochemical modifications which occurred during the neoformation of buds, it is possible to distinguish two distinct phases. The first phase starts immediately after the excision of the explants and continues for 30 h, when the mitotic index is at its highest. This corresponds to a phase of cellular activation, which is characterized by early synthesis of RNA, permitting the synthesis of proteins necessary for duplication of DNA and cell divisions. The second period starts after 30 h and ends after approximately 72 h of culture, at which time the first bud meristematic nodules were detected. This is a preparatory phase for organogenesis and above all related to synthesis of RNA and proteins.     

Does timing of boron application affect needle and bud structure in Scots pine and Norway spruce seedlings?

Loss of apical dominance is a well-known boron (B) deficiency symptom in trees. Recent field studies indicate that B deficiency may cause irreversible damage in emerging leader buds leading to bushy growth, and changes in developing needles in mature Norway spruce trees. We experimentally studied if timing of B application affects needles and buds of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) seedlings with low initial B levels. The treatments were: no B (B0); B supply from the beginning of the simulated summer (B1); starting soon after bud burst (B2) and starting at the occurrence of first needle primordia in new spruce buds (B3). At the end of the experiment, B concentration in B1 was 23 mg kg⁻¹ (pine) or 17 mg kg⁻¹ (spruce) and lower in the later applications. In B0 it was at deficiency limit. In B0, B2 and B3, there were fewer sclerenchyma cells, and cavities occurred in vascular cylinders in pine needles, and in spruce buds there were more tanniferous cells in the primordial shoots compared to B1. Furthermore, in all but B1 there was cell collapse in the bud apex of some spruce seedlings. The experimentally induced changes were the same as earlier reported in B deficient conifers in the field, and indicate, similarly as in the field that adequate B is necessary throughout the growing season for healthy growth, particularly for spruce. The differences between spruce and pines are due, at least partly, to the differences in time frame of needle development and in the differences in development of conducting tissues in the buds.     

Contribution of corticular photosynthesis to bud development in African baobab (Adansonia digitata L.) and Castor bean (Ricinus communis L.) seedlings

The African baobab (Adansonia digitata L.) and castor bean (Ricinus communis L.) are drought resistant green-stemmed succulent plants which grow in the arid and semi-arid regions of Africa. Photosynthesis in the stems of green-stemmed plants is known to contribute to plant carbon gain especially during leafless periods. To study the contribution of stem photosynthesis in stem succulent plants, the height and stem diameter of baobab and castor bean plants grown in the greenhouse were measured. The plants were completely defoliated and subjected to different treatments: Watered with open stems (WO), watered and stems covered with aluminium foil (WC) to achieve 100% light exclusion, drought and open (DO) and drought and covered (DC). Stem coverage with aluminium foil resulted in a higher stem height and diameter during drought for baobab with similar trends seen in castor bean. Light exclusion resulted in a significantly lower bud DW production and enrichment in ¹³C in bud dry matter of castor bean and in stem dry matter of baobab. These show that corticular photosynthesis contributes in carbon gain in these species.     

Breakdown of self-incompatibility during pistil development in Lycopersicon peruvianum by modified bud pollination

Summary Stylar self-incompatibility barriers in L. peruvianum can be avoided if pollen germination and growth through immature pistils is promoted under specific environmental conditions approximately 2–3 days before the initiation of anthesis. Since immature stigmas lack sufficient exudate for pollen germination, the sandwiching of a thin layer of pollen germination medium between the stigma and a mineral oil layer containing pollen allows precocious pollen germination and some compatible pollen tube growth through the style. This procedure is rapid, inexpensive, applicable in the field, and makes efficient use of pollen. Consistent though low seed yields have been obtained. A high proportion of aborted seed, seedling lethals, and aberrant seedling phenotypes in selfed progeny indicate the presence of strong post-zygotic barriers to such selfing. No evidence for a reduction in the strength of the SI response with increasing pistil age was observed.     

热击对麝香石竹茎段培养物培养效率的影响

本文研究了热击对麝香石竹茎段培养物培养效率的影响。结果表明,43℃2h热击麝香石竹茎段能促进或拟制不定芽的直接分化,提高愈伤组织的诱导率。热击愈伤组织能显著促进愈伤组织在继代培养基上的生长,但抑制愈伤组织在分化培养基上的生长。热击也能提高再生苗和愈伤组织的干重百分率。我们认为,热击所产生的生物学效应是与配合条件、特别是外源激素状况密切相关的。