A reactive pattern of ischemia-induced nestin protein in the rat brain

AIM:To explore the expressive profile of nestin protein in the focal ischemic brain and to study the recovery mechanism of brain focal infarct.METHODS:Cellular morphology,time-course and distribution pattern of nestin positive response were immunohistochemically examined in different brain regions of 36 adult male SD rats. RESULTS:Nestin positive response of different brain regions in sham operated rats was present in small- and micro-vasculartures and the third ventricle bottom and ependyma. A large number of nestin positive cells were detected in ischemic brain, and were more remarkable in the cortical areas of parietal lobe and preoptic area as well as ischemic caudoputamen. Stellate nestin positive cells were located in the deep layer of ischemic cortex, but fibrillary cells were located in the shallow layer. Nestin positive cells in the ischemic caudoputamen showed the same changes of morphology as those cells in the deep layer of ischemic cortex. Morphological and number alterations of nestin positive cells were the most remarkable at 1 weeks post-ischemia, which showed more hypertrophy and proliferation in morphology, and a marked increase in number was present in the ischemic cerebral cortex and the ischemic caudoputamen. These alterations of nestin positive cells persisted up to 6 weeks post-ischemia, and then, the nestin positive response in the ischemic brain decreased gradually.CONCLUSION:Focal cerebral ischemia induces nestin re-expression on reactive astrocytes, which may be very important to the self-recovery of cerebral infarct.     

Variation of Parthenium hysterophorus in response to soil quality: implications for invasiveness

Summary The performance of Parthenium hysterophorus , native to the tropical Americas and invasive to several countries, was evaluated for response to soil quality. Phenological (six stages) and quantitative growth variables [relative growth rates in height (R_h) and diameter (R_d)] were measured every fortnight. Based on harvest data, the variables, root:shoot (R:S) ratio, specific leaf area (SLA), relative growth rate in biomass (R_w), net assimilation rate (NAR) and dry matter allocation to plant components, were determined. High clay content in soils prolonged the rosette stage, enhanced R_h and R_d and hampered root growth, but promoted biomass allocation to shoots. The extreme degree of plant mortality was observed, with only 33.3% individuals surviving to reproduce in the soils with highest clay contents. This appears to be one of the most important findings that certainly has a major bearing on the range of adaptation of the weed. Seed mass declined whereas seed production increased in relatively coarser soils with the exception of nearly pure sand. In soils rich in clay, plants produced a smaller number of larger seeds. These data suggest that variation in fundamental functional traits would enable P. hysterophorus to adjust to a variety of habitat conditions.     

The ecological fitness of ALS-resistant Amaranthus retroflexus and multiple-resistant Amaranthus blitoides

Summary Field studies were conducted to evaluate the ecological fitness of Amaranthus spp. biotypes that evolved resistance to either acetolactate synthase (ALS) inhibitors ( A. retroflexus , SuR), to triazine herbicides ( A. blitoides , SuS/TR), or to both ( A. blitoides , SuR/TR), and estimate their ecological fitness under competitive conditions. The plants were grown in monoculture and in replacement series experiments. The examined mixtures were 100%S, 75%S/25%R, 50%S/50%R, 25%S/75%R and 100%R, at a constant stand of 400 plants m⁻². The SuR and SuS A. retroflexus biotypes attained similar shoot dry biomass per plant, biomass per plot and relative yield total (RYT) = 1. In monoculture, the final shoot biomass of A. blitoides biotypes SuS/TS plants was higher than that of SuR/TR and SuS/TR. A negative effect of association was observed, amensalism, when SuS/TS was grown in mixture with SuR/TR, in favour of the wild type. However, SuR/TR and SuS/TR biomass was not influenced by the presence of the competitor. These data support the hypothesis that the ALS-resistance trait in A. retroflexus and A. blitoides is not associated with growth penalty and did not incur ecological cost in the field. We suggest that the cause of the observed reduction in growth rendering the SuS/TR and SuR/TR less fit than the wild type is due to the triazine resistance, and may facilitate their dissipation.     

Restoration of tuber production by exposure to unshaded daylight in Eleocharis kuroguwai Ohwi shaded during the early tuber formation period

The loss of final tuber weight of Eleocharis kuroguwai Ohwi by shading during the early tuber formation period (TFP) is overcome by exposure to unshaded daylight thereafter (late TFP). In the present study, the growth parameters that contribute to the dry matter increase (DMI) per day of tubers in the late TFP were examined. DMI of the tuber during the late TFP was determined by that of the whole plant and the ratio of the DMI of the tuber to that of the whole plant during this period. The ratio of the DMI of the tuber to that of the whole plant during the late TFP was significantly correlated with the DMI of the whole plant during the first 14 days of the late TFP. During the late TFP after the exposure to unshaded daylight, DMI of the whole plant correlated with the surface area of the stem (SAS) and net assimilation ratio (NAR), and the SAS correlated with the stem dry weight (DW) and specific stem-surface area (SSA). SSA negatively influenced NAR, but NAR was increased by unshading. During the late TFP after shading, the effect of the decrease of the stem DW due to shading on the DMI of the whole plant was mitigated by the large SAS and high NAR. These results indicate that the growth parameters that contribute to the DMI of tuber during the late TFP after exposure to unshaded daylight are SAS and NAR just after unshading, and SSA during this period.     

土壤改良对越桔生长的影响

在盆栽条件下,对生长越桔的土壤进行改良。通过土壤pH值的变化、生长量及相关指标的分析对比,获得适合越桔生长的土壤改良类型。试验研究表明,pH值4.0～5.0的苔藓 草炭 原土 S土壤改良类型适合于越桔的生长,植株的高度、粗度、基生枝数等都明显增加。从各指标上观察,原土 2S的土壤改良类型也具有一定优势,说明在土壤有机质充足的基础上,只需调酸,越桔就能正常生长。     

松口蘑的研究热点

揭开松口蘑与松科植物的共生关系，开发松口蘑的人工栽培技术已成为国际性的松口蘑研究课题。近年来，日本、瑞典、美国、韩国和新西兰等国的研究人员为鉴别松口蘑及其近缘种提供了有效的分子生物学手段，从形态解剖学、生理学上验证了松口蘑是典型的外生菌根菌的理论，同时也提出了松口蘑-宿主是一个动态的共生关系。松口蘑快速人工菌根的合成体系已经建立，为松口蘑人工子实体的诱导奠定了不可缺少的基础。这一领域的研究必将与植物学、菌物学和土壤学的研究紧密地结合起来，以共同开发松口蘑的人工栽培技术。     

非自然越夏区小麦白粉病模拟鉴定病圃

作者于1990～1995年根据陕西省关中麦区小麦白粉病侵染循环特点,人工模拟自然发病条件,在非自然越夏区杨陵(省农科院试验地)成功地建立起白粉病菌可周年存活,且秋、春季均能充分诱发感染的混合菌系病圃,宜对小麦种质材料进行全生育期抗白粉病鉴定。利用该病圃已对陕西省1000余份小麦品种(系)及部分国内外抗源亲本材料做了抗病性鉴定和利用评价。     

丙硫磷控制稻瘟病的作用方式及应用技术

经１９９３－１９９５年生物测定和田间多点试验示范发现；１．丙硫磷对稻瘟菌孢子萌发和附着胞形成有显著的抑制活性，ＥＣ５０为１０３．３ｍｈ／Ｌ，５００ｍｇ／Ｌ的抑菌率达９６．２％；２．丙硫磷１０００ｍｇ／Ｌ对水稻苗叶瘟和穗瘟的预防效果分别为７９．４％和９０．７％，治疗效果分别为３９．３％和４１．８％；３丙硫磷６００－９００ｇ／ｈｍ＾２防治双季稻和瓜后稻穗瘟病的田间小区效果分别为７０．８％－８０．２％和     

Neurospora crassa对三唑醇的抗药性分子机制研究

 通过紫外光诱变获得Neurospora crassa对三唑醇杀菌剂抗性突变体"Nc70"。用2.5μg/ml三唑醇处理,突变体内甲基甾醇与脱甲基甾醇比例变化幅度远远小于亲本敏感菌株"STA"。突变体对三唑醇的吸收能力与敏感菌株相似,但药剂在体细胞内积累较少。三唑醇处理N.crassa 2 h后,药剂在菌体内的含量趋向稳定,突变体内的药量较敏感菌体低56.1%,而麦角甾醇合成量则高于敏感菌株53.7%。     

盐池半荒漠风沙区土地沙漠化发生发展规律的研究

本文耐盐池半荒漠风沙区土地沙漠化发生发展规律进行了探讨，主要分析了在土地沙漠化的过程中土壤和植被的变化过程及其成因。