Studies on Some Properties of the Apoplastic β-N-Acetyl-D-Hexosaminidase from Tomato Leaves

Some properties of the β-N-acetyl-D-hexosaminidase purified from intercellular fluid of tomato leaves after the plant was systematically infected by TMV (tobacco mosaic virus) were studied. When pNP β-D-GlcNAc (p nitrophenyl-N-aeetyl β-D-glucosaminide) or pNP β-D- GalNAc (p-nitrophenyl-N-acetyl-β-D galactosaminide) was used as the substrate, it showed the optical pH between 4. 8--5.0 and optical temperature between 44— 47℃. Studies of thermostabillty indicated that the enzyme had a biphasic denaturation curve. Using pNP-β-D-GIcNAc or pNP-β-D GalNAc as the substrate, the Km value of the enzyme was 0. 36 and 0. 67 mmol/L respectively. N acetyi-D glucosamine and N acetyl-D-galactosamine were competitive inhibitors of the enzyme activities. Ag+ and Hg2+ were sensitive inhibitors and Fe2+ . Fe3+ and Cu2+ were also inhibitors enzyme activities.     

An improved method for the generation and transfection of protoplasts from Cucumis sativus Cotyledons

Summary A protocol was developed for the preparation of Cucumis sativus var Straight 8 protoplasts that incorporates a two-step Ficoll^® gradient and results in a high percentage of viable, debris-free protoplasts suitable for the transient expression of foreign genes. Polyethylene glycol and electroporation were compared for their effect on protoplast transfection with commonly used reporter genes. Using a polyethylene glycol method, cucumber protoplasts transfected with a plasmid containing the -glucuronidase gene showed high expression levels, while protoplasts transfected with a plasmid containing the chloramphenicol acetyl transferase gene showed levels of activity that were barely distinguishable from mock-transfected controls. Tomato ringspot virus genomic RNA was also transfected into the protoplasts, and the assembly of viral particles was confirmed.     

The modifying effect of gibberellic acid and kinetin on the growth abnormalities induced by 2,4-D in marrow seedlings and the possible involvement of endogenous ethylene

Swelling of the hypocotyl base induced by 2,4-D in seedlings of marrow was much reduced if GA₃ was also present in the incubation medium. At appropriate concentrations kinetin also counteracted this 2,4-D effect, although at higher concentrations appeared to be ineffective. GA₃ was also able to overcome the inhibitory effects of 2,4-D on extension growth in the hypocotyl but kinetin was much less effective in this case. None of the treatments employed was able to alleviate the inhibition of radicle extension induced by 2,4-D.Ethephon induced similar responses in the seedlings to those resulting from 2,4-D treatment, while treatment with a mixture of 2,4-D and CoCl₂ removed many of these growth abnormalities. These observations are interpreted as indicating that 2,4-D operates at least partly by stimulating the production of ethylene in the tissues. 2,4-D strongly inhibited the accumulation of endogenous gibberellin during the period of seedling development examined, but enhanced cytokinin levels during the later stages of the same period. The possibility of interactions at the biosynthetic level between gibberellins, cytokinins and ethylene and their involvement in the regulation of seedling development are discussed.     

Cytopathology of Tomato torrado virus Infection in Tomato and Nicotiana benthamiana

Electron microscopy studies were carried out to investigate the cytopathological changes induced in tomato leaves by Tomato torrado virus (ToTV) that infects tomato plants worldwide causing severe necrotic symptoms. Plants infected with one of the Polish isolates of ToTV were used for cytopathological research. The results revealed severe cellular alterations, especially in Solanum lycopersicum. Moreover, it was shown that crystalline aggregates of virions occurred not only within the phloem cells as it has been previously reported.     

Influence of extremely low-frequency electric fields on the growth of Vigna radiata seedlings

The biological effects of extremely low-frequency electric fields (ELF) on living organisms have been explored in many studies, but the results are controversial and only a few studies investigated the influence of the intensity of the applied field on seedling growth. Here we assess the effects of a 50 Hz sinusoidal electric field on the early growth of Vigna radiata seedlings while varying the field intensity. Experiments performed in a dark, constant-climate chamber on several thousands of seedlings show that the field produces an inhibitory effect at a low field intensity and an enhancing one at a higher intensity. The maximum negative effect occurs at about 450 V/m, which is an intensity much lower than the exposure limits currently in force in the safety regulations.     

NaCl对大麦幼苗根系蛋白质和游离氨基酸含量的影响

大麦幼苗在２００ｍｍｏｌ／ＬＮａＣｌ处理６ｄ过程中,根中蛋白水麦活性下降,可溶性蛋白含量在处理１、２、４ｄ下降,６ｄ时有所提高。多数游离氨基酸相对含量及其总量呈上升势,胁迫１、２、６ｄ时,总量较对照分别上升６４．２０％、５６．６９％和１．６９％,其中Ｐｒｏ、Ｇｌｕ、Ａｌａ和Ｔｈｒ较为突出,盐胁迫下根系质膜和液泡膜结合慢白含量上升。可溶性蛋经ＳＤＳ－ＰＡＧＥ电泳和扫描分析,在盐胁迫１、２、６ｄ中２５     

Pollenfertility and seed formation in theOrnithogalum umbellatum/angustifolium complex (Liliaceae/Scilloideae)

The pollen fertility and seed formation of six species of theOrnithogalum umbellatum/angustifolium complex and of seven related species were studied. Four types of pollen grains could be recognized. The pollen fertility varied greatly in this complex and is not related to the ploidy level. The seed formation ofO. umbellatum showed an adaptation to a subcontinental-Mediterranean climate, that ofO. angustifolium to an Atlantic climate. In both cases raindrops seem to be important for pollination, in view of the absence of insect pollinators. After open pollination 113 seedlings were obtained in four species. Their chromosome numbers were determined. Nearly all the cultivated seedlings were aneuploid, which points to a positive selection of euploids in nature, because aneuploid individuals are rare in the wild.Biosystematic Studies on theOrnithogalum umbellatum/angustifolium Complex III.—Previous parts of this series are Part I: Taxonomy. Proceeding Kon. Ned. Acad. Wet. series C,85 (4), 563–574 (1982) andvan Raamsdonk (1984).     

地中海沿岸沙丘微生境对幼苗出现时空格局的影响

实验样地设在地中海沿岸沙丘,选择了3个不同的微生境代表：(1)稳定沙丘上的开阔地片段,(2)稳定沙丘上的灌丛下区域,(3)不稳定沙丘的路径区域;从2001年11月至2002年4月的整个生长季节,每一个微生境出现的幼苗在4个日期被监测,并在每一个取样日把每一株幼苗鉴定、计数后,用剪刀把地上部分移去;研究调查了3种微生境幼苗出现的时空分布格局,并分析了雨量与幼苗出现数量的关系。结果发现：在地中海沿岸沙丘生态系统,幼苗出现在时间上具有明显的分布特征,大多数幼苗出现在第一观测期,整个生长季幼苗都不断出现,但幼苗出现的数目却逐渐下降;各功能群的幼苗占幼苗总数的比例分别为：1年生阔叶草47．4％,多年生阔叶草2．5％,豆科植物17,0％,菊科植物14．5％,1年生禾草为11．7％,多年生禾草为1．9％,十字花科植物3．7％,伞形科植物1,4％。在空间上,总幼苗密度、物种丰富度和物种多样性等显示出重要的微生境差异,开阔地区域具有最大的幼苗密度、物种丰富度和物种多样性;3个微生境的幼苗出现不是同步的,微生境影响种子萌发的时间分布格局,灌丛下种子萌发具有滞后现象;大多数功能群的幼苗密度分布基本上具有显著的微生境差异,主要物种的幼苗分布也具有显著的微生境差异。雨量和萌发的幼苗数量间未发现显著的关系。     

Zn、Cd及其复合对小麦幼苗吸收Ca、Fe、Mn的影响

研究了溶液培养条件下Cd、Zn及其复合对小麦幼苗吸收Ca、Fe、Mn的影响.结果表明,小麦幼苗对Zn、Cd的吸收随溶液中Cd²⁺、Zn²⁺浓度的升高而增加,Cd、Zn同时存在时与其单独作用时幼苗对它们的吸收不同,Zn影响幼苗对Cd的吸收,Cd对Zn的吸收起抑制作用.Ca、Mn的吸收随溶液中Cd²⁺、Zn²⁺浓度升高而呈下降趋势,在Cd单独处理组和Zn单独处理组中Fe的吸收随Cd²⁺、Zn²⁺浓度升高而增加,但在Zn+Cd处理组中,Fe的吸收则呈下降趋势,其效应方式还与作物具体部位有关.