γ射线诱发大鼠胚胎细胞转化与N－ras的激活

以γ射线诱发转化的大鼠胚胎细胞(REC:myc:γ33)的DNA构建粘粒基因库,用总基因库DNA转染NIH/3T3细胞,产生转化灶的DNA作二轮转染,二轮转化的NIH/3T3细胞内有大鼠REC:myc:γ33DNA中具转化活性的N-ras基因,用不对称PCR和DNA序列分析法证明,REC:myc:γ33细胞中鼠N-ras的活化是由于第61位密码子的A→G点突变.NIH/3T3转化灶中鼠N-ras也有同样点突变,但NIH/3T3细胞的内源性N-ras基因则无此突变.     

鲑鱼生长激素基因分泌型表达质粒的构建

生长激素(GH)是动物垂体前叶分泌的一种多肽类激素.应用分子重组及PCR等技术,构建了一种鲑鱼生长激素基因分泌型表达质粒pOsGH153,使编码鲑鱼生长激素成熟肽的序列克隆在大肠杆菌分泌型表达载体PIN-Ⅲ-ompA内,直接位于编码大肠杆菌外膜蛋白A信号肽序列的下游,在Lpp-Lac杂合启动子控制下,经IPTG诱导,分子量约23 000的鲑鱼生长激素在大肠杆菌中获得高效表达,该产物具有天然鲑鱼生长激素的免疫活性,直接分泌到细胞周质,而信号肽被自动剪除.     

植物激素与营养液配施对平菇产量和品质的影响

不同配比的ＧＡ＿３和ＫＴ与营养液配施,对平菇菌丝生长影响不同。ＧＡ＿３和ＫＴ的适当配比,能促进菌丝分枝生长,也能显著提高平菇子实体的产量和品质,但维生素Ｃ的含量有所下降。ＧＡ＿３和ＫＴ若与营养液配合施用,比单独施用更能发挥其促进作用。     

氮肥和底墒对小麦籽粒灌浆过程的调节效应分析

以氮肥和底墒为决策变量,采用最优二次Ｄ饱和设计,用Ｌｏｇｉｓｔｉｃ方程拟合各水肥处理的籽粒充实过程,并推导出一系列次级参数,分别建立了小麦籽粒灌浆强度与持续时间参数的数学模型。结果表明：生长在氮肥或底墒逆境条件下的小麦受精子房的生长潜势（Ｃｏ）较大,并随逆境条件的改善而降低;千粒重（Ｙｏ）与灌浆快增期（Ｔ）的长短、最大灌浆速率（Ｒ＿（ｍａｘ））和平均灌浆速率（Ｒ）无明显相关性,却与起始生长势、灌浆系数（Ｔ·Ｒ＿（ｍａｘ））高度正相关,并且千粒重与灌浆系数的相关性明显大于千粒重与起始生长势的相关性;氮肥和底墒对籽粒灌浆特性具有显著的调节作用。同时还阐述了调节这些参数的水肥栽培途径。     

结球甘蓝离体下胚轴愈伤组织的维管组织及管状分子

结球甘蓝离体下胚轴培养初期,在切口较深层发现的维管组织结节,是由外植体维管组织衍化的。愈伤维管组织既可由愈伤薄壁细胞分化,也可由愈伤形成层分化。愈伤形成层向内分化导管分子,向外没有发现筛分子的分化。愈伤维管组织有不同的形态,起初常各不相连,后和外植体维管组织衔接。芽的再生起初和愈伤维管组织没有直接的联系,后原形成层自上而下分化,逐渐与愈伤维管组织相连接。不定根发生于维管组织结节的单向极性分化,始终     

几种环境因素对玉米叶切块光诱导的影响

利用液相氧电极研究了暗处理、光强、ＣＯ２水平、缺钾和干旱对玉米叶切块光诱导的影响。发现长时间的暗处理、高光强、低ＣＯ２浓度、缺钾和干旱均使光合诱导期拉长。影响光合诱导期的外界逆境如低ＣＯ２浓度、缺钾和干旱也使玉米叶片的净光合速率下降,并对这些结果产生的原因作了分析。     

热带林茎流收集及计算方法探索

热带林茎流收集及计算方法探索周光益,吴仲民,李意德,陈步峰（中国林科院热带林业研究所,广州５１０５２０）ＣｏｌｌｅｃｔｉｏｎａｎｄＣａｌｃｕｌａｔｉｏｎＭｅｔｈｏｄｓｆｏｒＳｔｅｍｆｌｏｗｉｎＴｒｏｐｉｃａｌＦｏｒｅｓｔ．￥ＺｈｏｕＧｕａｎｇｙｉ;Ｗ...     

Hydraulic properties of sphagnum peat moss and tuff (scoria) and their potential effects on water availability

The importance of macrostructure to root growth of ryegrass (L. perenne) seedlings sown on the soil surface was studied in two soils in which the macrostructure had resulted mainly from root growth and macro-faunal activity. Sets of paired soil cores were used, one of each pair undisturbed and the other ground and repacked to the field bulk density. Undisturbed and repacked soils were first compared at equal water potentials in the range −1.9 to −300 kPa. At equal water potential, the undisturbed soil always had the greater strength (penetration resistance), and root growth was always greater in the repacked soil with no macrostructure than it was in the soil with macrostructure intact. At equal high strength (low water potentials) it appeared that root growth was better when soils were structured. When strength was low (high water potentials), root growth was better in the unstructured soil. Soils were then compared during drying cycles over 21 days. The average rate at which roots grew to a depth of 60 mm, and also the final percentage of plants with a root reaching 60 mm depth, was greatest in repacked soils without macrostructure. The species of vegetation growing in the soil before the experiment affected root growth in undisturbed soil; growth was slower where annual grasses and white clover had grown compared with soil which had supported a perennial grass. It appears that relatively few roots locate and grow in the macrostructure. Other roots grow in the matrix, if it is soft enough to be deformed by roots. Roots in the matrix of a structured soil grow more slowly than roots in structureless soil of equal bulk density and water potential. The development of macrostructure in an otherwise structureless soil, of the type studied, is of no advantage to most roots. However, once a macrostructure has developed, the few roots locating suitable macropores are able to grow at low water potential when soil strength is high. The importance of macrostructure to establishing seedlings in the field lies in rapid penetration of at least a few roots to a depth that escapes surface drying during seasonal drought. ei]{gnB E}{fnClothier}     

Physiological and Environmental Requirements for Poplar (Populus deltoides) Bark Storage Protein Degradation

In poplar (Populus deltoides Bartr. ex Marsh), a 32-kD bark storage protein (BSP) accumulates in the bark during autumn and winter and declines during spring shoot growth. We investigated the physiological and environmental factors necessary for the degradation of poplar BSP. Poplar plants were exposed to short-day (SD) photoperiods for either 28 or 49 d. Plants exposed to short days for 28 d formed a terminal bud but were not dormant, whereas exposure to short days for 49 d induced bud dormancy. BSP accumulated in bark of plants exposed to both SD treatments. The level of BSP declined rapidly when nondormant plants were returned to long days. BSP levels did not decline in dormant plants that were exposed to long-day (LD) conditions. If dormant plants were first treated with either low temperatures (0[deg]C for 28 d) or with 0.5 M H2CN2 to overcome dormancy and then returned to long days, the level of BSP declined. Removal of buds from non-dormant or dormant plants in which dormancy had been overcome inhibited the degradation of BSP in LD conditions. BSP mRNA levels rapidly declined in plants exposed to long days, irrespective of the dormancy status of the plants or the presence or absence of buds. These results indicate that the buds of poplars are somehow able to communicate with bark storage sites and regulate poplar BSP degradation. These results further support an association of BSP mRNA levels with photoperiod because short days stimulate BSP mRNA accumulation, whereas long days result in a decline of BSP mRNA abundance.     

Salicylic acid inhibits the biosynthesis of ethylene in detached rice leaves

The effects of salicylic acid (SA) on ethylene biosynthesis in detached rice leaves were investigated. SA at pH 3.5 effectively inhibited ethylene production within 2 h of its application. It inhibited the conversion of ACC to ethylene, but did not affect the levels of ACC and conjugated ACC. Thus, the inhibitory effect of SA resulted from the inhibition of both synthesis of ACC and the conversion of ACC to ethylene.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - EFE ethylene-forming enzyme - SA salicylic acid