关于水稻根负向光性光受体的探讨

为了研究水稻根负向光性的光受体,观察了光质对稻根的负向光性效应,用紫外 可见分光光度计测定了水稻根冠浸提液的吸收光谱,并对根冠中的蛋白质进行了SDS PAGE电泳分析。蓝紫光能显著诱导稻根负向光性,而红光无效;根冠浸提液的吸收光谱在350 nm和450 nm各有一个吸收峰;根冠中有120 kD的光受体特征的蛋白条带。推测稻根负向光性的光受体可能为蓝光受体。     

Calcium Signaling is Involved in Negative Phototropism ofRice Seminal Roots简

Calcium ions(Ca2+) act as an intracellular second messenger and affect nearly all aspects of cellular life. They are functioned by interacting with polar auxin transport, and the negative phototropism of plant roots is caused by the transport of auxin from the irradiated side to the shaded side of the roots. To clarify the role of calcium signaling in the modulation of rice root negative phototropism, as well as the relationship between polar auxin transport and calcium signaling, calcium signaling reagents were used to treat rice seminal roots which were cultivated in hydroculture and unilaterally illuminated at an intensity of 100–200 μmol/(m2·s) for 24 h. Negative phototropism curvature and growth rate of rice roots were both promoted by exogenous CaCl2 lower than 100 μmol/L, but inhibited by calcium channel blockers(verapamil and LaCl3), calcineurin inhibitor(chlorpromazine, CPZ), and polar auxin transport inhibitor(N-1-naphthylphthalamic acid, NPA). Roots stopped growing and negative phototropism disappeared when the concentrations increased to 100 μmol/L verapamil, 12.500 μmol/L LaCl3, 60 μmol/L CPZ, and 6 μmol/L NPA. Moreover, 100 μmol/L CaCl2 could relieve the inhibition of LaCl3, verapamil and NPA. The enhanced negative phototropism curvature was caused by the transportation of more auxin from the irradiated side to the shaded side in the presence of exogenous Ca2+. Calcium signaling plays a key role as a second messenger in the process of light signal regulation of rice root growth and negative phototropism.     

白蚁的行为概述

白蚁由于生活隐蔽其行踪不易被发现,其生活习性与行为更不易为人们所了解。在综述了白蚁繁殖、建筑、取食、防卫及向光性等行为后,提出了利用白蚁的一些行为特征进行合理控制的建议。     

Effect of Indoleacetic acid （IAA） on the Negative Phototropism of Rice Root

To explore the effects of IAA on negative phototropism of rice (Oryza sativa L) root, agar block containing IAA was unilaterally applied on root tip to examine the phototropic response of root to exogenous IAA, and microstructure of the bending part was observed with an optical microscope. The growth of seminal roots could be regulated by exogenous IAA as well as light,as a result the root bent towards the site treated, causing asymmetric growth of the root cells at the elongation zone and consequently bending growth. IAA concentration in the shaded side of adventitious root increased much greater at 1.5 h after the start of irradiation. The unequal lateral IAA distribution can be concluded to be the main cause for negative phototropism of rice root.     

Germination ecology, emergence and host detection in Cuscuta campestris

Trials were carried out to study the germination and dormancy of Cuscuta campestris Y. (dodder) seeds and factors influencing the success of early parasitisation of sugarbeet. Primary dormancy can be removed by seed scarification. Germination was negligible at 10°C and optimal at 30°C, while it was not influenced by light. Seed burial induced a cycle of induction and breaking of secondary dormancy. Seedling emergence was inversely proportional to the depth of seed burial and only seed buried within 5 cm of the soil surface emerged. Storage of C. campestris seeds in a laboratory for 12 years resulted in the loss of primary dormancy, enabling the germination of all viable seeds. Host infection (i.e. protrusion of parasite haustoria from host tissue) was heavily influenced by host growth stage. Tropism towards a host was due to the perception of light transmitted by green parts of sugarbeet plants. Insertion of a transparent glass sheet between host leaves and parasite seedlings did not modify this response. This phototropism permitted Cuscuta to identify host plants with high chlorophyll content as a function of the lower red/far red ratio of transmitted light.     

Phototropism and Phytochrome

向光性是植物为捕捉更多光能而建立起来的对不良光照条件的适应机制之一．蓝光被证明是引起植物向光性最有效的光源．最近的研究进一步揭示植物体内一定存在一种对蓝光具特殊敏感性从而引起向光性反应的光受体．光生物学家已克隆得到数种ｃＤＮＡ并证明它们当中至少有一种对向光性受体负责,遗憾的是至今并没有弄清楚到底是哪一种ｃＤＮＡ表达向光性受体．就诱导向光性反应而言,红光是无效的,但早在本世纪５０年代就已有人证明红光对植物向光性行为产生深刻影响．最新的研究（Ｌｉｕ＆Ｉｉｎｏ１９９６）已证明红光对蓝光所诱导向光性的影响是由光敏色素这一红光／远红光受体参与调节的．研究发现对蓝光和远红光敏感的向光性受由对红光敏感的光敏色素的严格控制．绝对黑暗条件下生长的植物向光性蓝光刺激无反应,不表现向光性．这样的植物只有接受了红光或远红光前处理后才对向光性蓝光刺激有反应．这一重大发现揭示了向光性反应中光敏色素与向光性受体的相互作用,并为光生物学家彻底搞清楚植物向光性受体提供了一条全新的研究思路．本文就是在这一背景基础上总结了近几年来有关光敏色素和向光性方面研究的新进展．我们希望通过这样的工作能使有关植物向光性受体和植物体内吸收不同波长光的光受体     

Effect of Indoleacetic acid (IAA) on the Negative Phototropism of Rice Root

To explore the effects of IAA on negative phototropism of rice ( Oryza sativa L.) root, agar block containing IAA was unilaterally applied on root tip to examine the phototropic response of root to exogenous IAA, and microstructure of the bending part was observed with an optical microscope. The growth of seminal roots could be regulated by exogenous IAA as well as light,as a result the root bent towards the site treated, causing asymmetric growth of the root cells at the elongation zone and consequently bending growth. IAA concentration in the shaded side of adventitious root increased much greater at 1.5 h after the start of irradiation. The unequal lateral IAA distribution can be concluded to be the main cause for negative phototropism of rice root.     

钙信号试剂对水稻种子根负向光性生长的影响

 为了探讨水稻根负向光性形成与钙信号传导的关系,以水稻种子根为材料,用不同浓度的钙信号试剂\[氯化钙、钙通道有机阻断剂异搏定、钙通道无机阻断剂氯化镧、钙调素抑制剂氯丙嗪（CPZ）以及生长素极性运输抑制剂NPA\]处理水稻种子根,以1/10 Hoagland培养液为对照,并用100~200 μmol/(m2·s)单侧光照射24 h。实验结果表明,适量的CaCl2使水稻种子根负向光性增强并使其生长加快,负向光性增强是由于外源Ca2+进一步促进生长素从向光侧向背光侧运输引起的,与生长速率加快无关;同时,随着钙通道有机阻断剂、无机阻断剂、钙调素抑制剂以及生长素极性运输抑制剂浓度的上升,水稻根的负向光性及生长均受显著抑制,当异搏定的浓度大于100 μmol/L,LaCl3的浓度大于12.5 μmol/L,负向光性消失,种子根的生长也受到严重的影响;而60 μmol/L钙调素抑制剂氯丙嗪、6 μmol/L 生长素极性运输抑制剂NPA也使得根负向光性消失,根的生长几乎停止;向LaCl3溶液、异搏定溶液以及NPA溶液中添加100 μmol/L CaCl2可使负向光性及生长速率得到不同程度的恢复,表明钙离子作为第二信使系统,与生长素相互作用,参与光信号调控水稻根生长和负向光性形成。     

cpt1基因与水稻根负向光性的关系

为了研究cpt1基因与水稻根负向光性运动的关系,探讨IAA横向运输与水稻根负向光性运动的关系。检测了外源试剂CaCl₂、EDTA以及IAA对水稻根的负向光性运动的效应,并采用RT-PCR的方法验证了不同外源试剂对cpt1基因表达的影响。结果表明,水稻根经光照24 h后,与对照相比,1 mg L^-1的CaCl₂和0.001 mg L^-1的IAA能明显促进水稻根负向光性的弯曲生长,1 mg L^-1的EDTA(CaCl₂的抑制剂)明显抑制水根负向光性的弯曲生长;cpt1基因的表达受上述外源试剂诱导,并表现与水稻根的负向光性生长呈明显的正相关性,推测IAA的横向运输及其运输载体CPT1蛋白对水稻根的负向光性运动具重要作用。