the,plant,cell贴吧

篇一：The Plant Cell

The Plant Cell 21:1328-1339 (2009)

? 2009

REVIEW The Angiosperm Gibberellin-GID1-DELLA Growth Regulatory Mechanism: How an "Inhibitor of an Inhibitor" Enables Flexible Response to Fluctuating Environments

Nicholas P. Harberd1, Eric Belfield and Yuki Yasumura

Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom 1 Address correspondence to .

ABSTRACT

The phytohormone gibberellin (GA) has long been known to regulate the growth, development, and life cycle progression of flowering plants. However, the molecular GA-GID1-DELLA mechanism that enables plants to respond to GA has only recently been discovered. In addition, studies published in the last few years have highlighted previously unsuspected roles for the GA-GID1-DELLA mechanism in regulating growth response to environmental variables. Here, we review these advances within a general plant biology context and speculate on the answers to some remaining questions. We also discuss the hypothesis that the GA-GID1-DELLA mechanism enables flowering plants to maintain transient

growth arrest, giving them the flexibility to survive periods of adversity.

篇二：Plant Cell

Original Paper

The effects of genotype, inflorescence

developmental stage and induction medium on callus induction and plant regeneration in two Miscanthus species

K. G?owacka1 11, S. Je?owski and Z. Kaczmarek

(1) Institute of Plant Genetics, Polish Academy of Sciences, ul. Strzeszyńska 34,

60-479 Poznań, Poland

K. G?owacka

Email: uszepti@tlen.pl

Received: 3 March 2009 Accepted: 4 February 2010 Published online: 25 February 2010 Abstract

Several grass species of the genus Miscanthus are considered to be outstanding candidates for a sustainable production of biomass to

generate renewable energy. The purpose of this study was to investigate the effects of genotype, the developmental stage of the explant donor inflorescence and the induction medium on the success rate of

micropropagation. The experiments were conducted on three genotypes of M. sinensis and one of M. x giganteus. Explants from the youngest inflorescences (0.1–2.5 cm in length) showed a significantly higher callus induction rate than those from more developed inflorescences (2.6–5 cm in length). In addition, cultures initiated from explants from the youngest inflorescences showed significantly the highest rates of callus regeneration and the highest shoot regeneration rate. Three out of the four genotypes tested showed the best shoot regeneration from calli initiated from the youngest inflorescences when cultured on the Murashige and Skoog basal medium (MS) with 5 mg l?1 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.1 mg l?1 6-benzyladenine (BA). The percentages of calli from those genotypes showing regeneration ranged from 45 to 76.7%, and the corresponding shoot regeneration rates ranged from 1.85 to 6.33

shoots/callus. This demonstrates that, with some adjustments, efficient micropropagation of Miscanthus sp. is feasible.

Keywords Miscanthus sinensis - Miscanthus x

giganteus - Micropropagation effectiveness - Callus induction - Plant regeneration

Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid

- BA 6-benzyladenine

- CIR Callus induction rate

- CRP Callus regeneration percentage

- IAA Indole-3-acetic acid

- KIN 6-furfurylaminopurine (kinetin)

- NAA 1-naphthaleneacetic acid

- SRR Shoot regeneration rate

Introduction

Species from the genus Miscanthus are perennial giant grasses from East Asia, some of which were introduced to Europe from Japan in 1935 (Greef and Deuter 1993; Linde-Laursen 1993). Because of their C4 type

photosynthesis and high water-use efficiency, they tend to offer a very high potential for biomass production. A Miscanthus crop is potentially an efficient, sustainable, multifunctional and environmentally friendly biomass producer, making it very suitable and promising for the production of biofuels and fibre in Europe (Lewandowski 2006; Lewandowski and Schmidt 2006). In the near future, grasses from the genus Miscanthus will likely play an important role in sustainable agriculture (Lewandowski and Heinz 2003; Lewandowski 2006; Christian et al. 2008).

Within the genus, M. x giganteus and M. sinensis are considered to be the most valuable for biomass production. Of the two, M. x giganteus is a sterile triploid hybrid between diploid M. sinensis and tetraploid M. sacchariflorus (Linde-Laursen 1993); M. sinensis is fertile but

self-incompatible and produces highly variable progeny. Hence, for both species, vegetative propagation is the only method for a commercial-scale multiplication of plants. Species of Miscanthus have been propagated by rhizome division or by in vitro micropropagation. Despite a number of reports on the in vitro culture of M. x giganteus (Lewandowski 1997; Holme and Petersen 1996; Holme et al. 1997; Petersen 1997; Petersen et al. 1999), there is, as yet, no well-established or recommended method for the in vitro micropropagation of various Miscanthus species that would be suitable for commercial production.

In the present study, the micropropagation effectiveness of M. x giganteus and different M. sinensis genotypes were studied. The experiments

conducted were performed using the existing micropropagation techniques

for M. x giganteus with a range of modifications and with several newly established culture media for callus induction. In the process, the genotypic, developmental and culture medium effects were tested.

Materials and methods

Plant material

The experiments were conducted on two Miscanthus species: M. sinensis (2n = 2x = 38) and M. x giganteus (2n = 3x = 57). The former was

represented by three genotypes of different origins: 93 M0146010 (Ms10) is a European hybrid, 93 M0006002 (Ms17) originates from Japan and M0086 (Ms20) is a genotype named “Gro?e Font?ne” selected in Germany. M. x giganteus was represented by a single genotype, MG1.

In vitro culture

Cultures were initiated between May and August from tillers collected from plants grown without fertilisation in a ground greenhouse. The tillers had inflorescences ranging in length from 0.1 to 5 cm. The uppermost stem segments were cut at 1–2 nodes below the base of inflorescences. All foliage, except for 3–4 leaves outside the inflorescence, was removed. Cut stem segments were surface-sterilised for 20 min with 10% commercial ACE bleach (0.45% sodium hypochlorite) and rinsed three times in sterile water. To test the efficacy of in vitro culture, 1-mm segments of immature inflorescences were used as explants. Immature inflorescences ranging in length from 0.1 to 2.5 cm were classified as developmental stage A

(Fig. 1a, b) and those in the size range 2.6–5 cm as stage B (Fig. 1b).

Fig. 1 Micropropagation of Miscanthus through inflorescences delivered callus: (a) and (b—first four on the left) inflorescences at the developmental stage A; (b—first on the right) inflorescences at the developmental stage B; (c) shoot-forming callus (arrow)—k1; (d) compact, light cream callus—k2; (e) root-forming callus (arrow)—k3; (f) non-morphogenic callus—k4; (g) regenerants on rooting medium

The explants were cultured on five callus induction media, labelled M1–M5 (Table 1). These were based on either the B5 medium of Gamborg et al.

(1968), the SH medium of Schenk and Hildebrandt (1972) or the MS medium of Murashige and Skoog (1962). The M3 medium contained MS medium

supplemented with 5 mg l?1 2,4-dichlorophenoxyacetic acid (2,4-D) and 1,430 mg l?1 proline according to Holme and Petersen (1996), whereas M5 consisted of the MS medium supplemented with 5 mg l?1 2,4-D and 0.1 mg l?1 6-benzyladenine (BA) (Petersen 1997). The remaining three media (M1, M2, M4) were the basal media with the authors’ modifications. All media were adjusted to pH 5.70–5.75 prior to the addition of 0.8% agar and were autoclaved at 121°C for 20 min.

Table 1 Composition of the media used for the induction of callus

After 12 weeks incubation at 26 ± 2°C in the dark, the cultures were visually scored for their general appearance and the regeneration ability of callus pieces, and were classified into four classes (k1–k4) along the lines proposed by Lewandowski (1997), Holme and Petersen (1996) and Petersen (1997). A “callus piece” is understood here as a 1-mm piece of callus. Shoot-forming callus, classified as k1 callus (Fig. 1c), had a yellow-cream colour with translucent and light-green shoot-like

structures. The k2 callus was compact, white or light cream callus with a porous appearance (Fig. 1d); k3 callus was soft, watery, of a grey or pink colour with anthocyanin-coloured spots (Fig. 1e) and was

root-forming. The k4 callus was non-morphogenic and appeared as a soft, watery tissue with a light brown colour and a crystalline surface (Fig. 1f).

Plant regeneration from callus occurred on the MS medium supplemented with

12 mg l? BA (Holme and Petersen 1996) under a 16-h photoperiod (100 μmol m21? s?). Twenty percent of randomly chosen k1 callus pieces were transferred to the regeneration medium for 4 weeks, transferred to fresh medium for another 4 weeks and scored for the numbers of regenerated calli and shoots. For root induction, single shoots were transferred to the MS medium with 1 mg l?1 1-naphthaleneacetic acid (NAA) and kept at a 16-h-photoperiod regime for at least 2 weeks (Fig. 1g).

篇三：The Effect of Cadmium Stress On Plant Cell

The Effect of Cadmium Stress On Plant Cell

Abstract: Heavy metal is one of the pollutants which most seriously polluted our environment in our country. It has a serious harm not only on the ecological environment, but also to human body through the food chain enrichment. Cell is the basic structure and functional unit of plant, the response of plant to cadmium can be reflected by celluar change. From the aspects of heavy metals on the nucleus of the plant cell plasma membrane, chloroplasts, mitochondria, vacuoles, ultrastructure research progress on heavy metal damage was summarized, and the characteristics of plant cells damaged by heavy metal.

Key words: pollution; heavy metal; plant cell; toxicity; organelle

1. Introduction

Due to the rapid development of industry and agriculture, industrial wastewater emissions increased and extensive use of pesticides in agriculture, soil heavy metal pollution is increasingly serious and it has become the world serious environmental problems. Because of its high toxicity of cadmium,its migration be widespread concerned.

Cadmium is a non-essential elements of the plant, it is difficult to be degraded after removal of cadmium contaminated soil. Plants can absorb cadmium, lead to the accumulation of cadmium in agricultural products, enter the food chain through the soil crop system, thereby jeopardizing the biological health[1].

Cell is the basic structure and functional unit in a living body, including cell wall, cell membrane, nucleus and cytoplasm and there are mitochondria and chloroplasts, vacuoles in cytoplasm. In cadmium stress, growth and development of plants affected, directly reflected in the growth and development of cells are affected, this article briefly describes the cells on the absorption of cadmium, and the effects of cadmium on the cells.

2. The absorption of cadmium

There is a longstanding awareness in Japan and other Asian countries of the risks associated with Cd intake in general and the consumption of rice as the main source of Cd exposure. Rice is also the model system for monocot species, which explains why molecular knowledge regarding Cd accumulation is well advanced in rice, progressing beyond analysis of natural variation and identification of QTLs[2].

OsNramp5 (natural resistance-associated macrophage protein 5) has recently been identified as the major Cd uptake transporter in rice[3]. The protein is localized in the plasma membrane at the distal side of exodermis and endodermis cells. An nramp5 knockout mutant and RNAi lines grown in soil show a strongly reduced Cd concentration of the straw and the grain, corresponding with a much lower short-term uptake rate of rice roots for Cd. Other transporters, OsIRT1 (iron regulated transporter1), OsIRT2, and OsNramp1, are potentially implicated in Cd uptake, in particular upon reaeration of soil after flooding. These are Fe2+ transporters with limited specificity and induced under Fe deficiency. When pond water is released,

aerobic conditions arise which simultaneously decrease Fe availability as Fe2+ becomes oxidized; and also increase Cd availability as Cd sulfides are oxidized to more soluble sulfates[4]. OsNramp1 overexpression increases Cd sensitivity and Cd accumulation in leaves[5]. However,because OsNramp5 was shown to account for most of the rice Cd uptake under different Fe supply conditions, OsIRTs and OsNramp1 appear to play only a minor role in Cd uptake from the soil. Generally believed that the soil Cd mainly Cd2 + or cadmium chelate (Cd-chelate) into the plant root cells and accumulate in the apoplast, especially in the cell wall[6]. Part of the Cd across the membrane into the cytoplasm, Cd through the plasma membrane into the cytoplasm mainly through ZIP family transporter proteins (zinc-regulated transporter/iron-regulated transporter-like protein), transporter proteins of ZIP family are non-specific transport protein, Ca2+, Fe2+, Mn2+, Zn2+ and its transmembrane transport are related. Such as ZIP family AtIRT1 and TcZNT/TcZIP4 are related to the transmembrane transport of Cd2 +[7].

3. Effects of Cd stress on plant growth

3.1 Effects of Cd stress on structure and function of the nucleus

Nucleus is the most important intracellular organelles, where genetic information is stored, copied and places expression, nucleus is also life activity of cells and genetic features control center. Nucleus and nucleolus structure closely related to the state of the metabolic activity of the cells, once it is damaged,which will result in the expression of genetic information ircorrectly, a synthetic ribosome innormally,and evenmore affect intracellular protein synthesis and cell differentiation[8]. Gurpreet found that with 250 μmol/L of Pb2+ in wheat root tip cells treated nucleolus its nucleus becomes smaller, and the emergence of mass-like structure, when the amount of Pb becomes 500 μmol/L,after the disintegration of the nucleus[9]. So we can see the damage to the ultrastructure of nucleus of heavy metals mainly for: double nuclear membrane structure separation, the structure is damaged, condensed chromatin and nucleoli,appear the microkernel.

3.2 Effects of Cd stress on structure and function of the plasmalemma

Plasma membrane ACTS as a barrier to protoplast and its surrounding environment, which is a cell's portal, controls the cell signal transduction and substance exchange inside and outside, to maintain a relatively stable living environment in the cell, so that the cells become organisms a- basic unit of structure and function.When plant damage from heavy metal, the structure of plasma membrane is the first to be affected. Liu and Kottke have been proved that using the method of EELS that Cd2+ is contained in these high electron density particles, Cd2+ can be through the cytoplasmic membrane package form into cells, the number of Cd2+ free in order to reduce the cytoplasm, thus reduce the damage to cells[10].

3.3 Effects of Cd stress on structure and function of the chloroplast

Chloroplasts of plant cells are unique to the energy converter,whose ultrastructure and function are closely related to photosynthesis[11]. Chloroplast ultrastructure of heavy metal is more sensitive, its damage is usually one of the reasons caused plants

to die. Normal chloroplasts show long ellipsoid or fusiform, capsule and thylakoid structure clear, grana lamella or matrix arranged parallel to the long axis direction of chloroplasts, its internal containing a small amount of high electron density of small spherical lipid ball. Once under heavy metal stress, chloroplast obvious changes in the structure. Djebali processed tomato with Cd2+ ,such as the leaf ultrastructure was observed when found due to the expansion of the thylakoid membrane of chloroplasts in the shape of a twisted out of shape[12]. Rodrigo treated Gracilaria domingensis with Cd2+, observed the thylakoids of the chloroplast was destroyed, in the chloroplast plasmid ball, When the concentration of Cd2+ increase, the destruction of the thylakoid is more serious, plasmid ball not only increases in number,but aslo presents the various shapes[13]. The chloroplast membrane system is damaged, can make the enzyme of decomposition chlorophyll enhanced enzyme activity, resulting in the degradation of chlorophyll. Thylakoid damage will cause the enzyme in the synthesis of chlorophyll loses the skeleton and cannot play normal function, make the content of chlorophyll decreased. Decreased chlorophyll content will directly results in the decrease of the efficiency of the plant photosynthesis, thus the physiological and biochemical metabolism of plants produce a great toxicity. When the plants by other stresses, such as high temperature also appear the phenomenon that chloroplast stromal vacuolization and chloroplast thylakoid gradual loss of function of photosynthesis[14].

3.4 Effects of Cd stress on structure and function of the mitochondria

Mitochondria are the organelles to produce ATP in plant, through its oxidative phosphorylation, sugars and other organic matter can be transformed into ATP, as the organism's energy life activities，known as the "energy factories living body". Under normal circumstances, the mitochondria are more rules globose or ellipsoid, double membrane structure is complete, crest is clearly visible, are arranged randomly, a small amount of distribution in cytoplasmic matrix. aroslaw, etc processed cucumber leaf with Cd2+ found that the number of mitochondria in cells significantly less, and the emergence of spherical ridges[15]. Mitochondrial structure damage, can cause the internal system of electron transport and oxidative phosphorylation circulation suffocate suffocate, resulting in cellular respiration is abate, aerobic metabolism of sugar, ultimately affect the respiration of plants[16].

3.5 Effects of Cd stress on structure and function of the vacuole

Vacuole is derived from the endoplasmic reticulum or golgi membrane by the unit package of vesicle, its interior is a water soluble system, containing a large number of ions and metabolic substances, is a plant cell self mediation system and internal environment. Ge, treated poplar tree root meristem with Cd2+ then found that in its cytoplasm containing a large number of dense electronic particles utricle bubble, these follicles bubble are fused together to form the large vacuole[17]. Yu crystal, processed corn with Cd2 +,many sizes are also found in the root tip cells of vesicles, in these vesicles vacuole formed by visible particles to the high electron density, along with the increased density of Cd2 +, vacuole membrane was damaged, a large number of high electron density can be seen in the cytoplasm, cell disintegration[16]. Vacuoles is

the place where metabolism byproducts and waste hoarding in plant cell[18], its internal contains a variety of substances such as organic acid, organic alkali, protein can combine with heavy metals and heavy metal ions in the cell by segregation[19], the separation of heavy metals in a particular area, can reduce the damage to the cells[20]. So we can kown that vacuole of plant cells to prevent heavy metal poisoning itself plays an important role in protection.

3.6 Effects of Cd stress on structure and function of the cell wall

Cell walls of plant cells is an important structure, with the protection and support role, and related with the passing transpiration of plants, material transport, water potential regulation and chemical signals, physical signals transmission. Normal plant cell wall structure is loose and thickness uniformity. XiaoXin [21] treated wheat seedling root tip cells with 0.5 mg/L of Cd2 + ,make the root tip cells to produce the serious deformation, a slight plasmolysis phenomenon, cells inside and outside the wall, and there is a certain amount of internal black sediments, cell wall thinning and show the canine tooth shape deformation. Heavy metals in the cell walls of precipitation is an important way of plant internal detoxification, which is associated with cell wall components.Cell wall is mainly composed of cellulose, hemicellulose and pectin, the pectin can provide large amounts of heavy metals in combination with ion exchange sites, so the cell wall has a strong cation accumulated ability, is the first barrier of heavy metals into the cells[22]. In recent Bouzon etc. [23] treated Hypneamusciformis with different concentration of Cd2+ also found the phenomenon of cell wall thickening, when this is due to the cell wall polysaccharide containing sulfuric acid esterification and Cd2+ formed the utricle bubble, and then incorporated into the cell walls. Thus, the influence of heavy metal in plant cell wall is mainly manifested in the morphological structure, or upset, or thin, or present a random changes.

3.7 Effects of Cd stress on structure and function of the other organelles

Stress of heavy metals in addition to the impact of these organelles, the endoplasmic reticulum, golgi apparatus, such as the ribosome organelles also exist. In normal plant cells, the ribosome in cell matrix across the endoplasmic reticulum and more tidy, golgi apparatus, the surface is smooth, vesicle much focus on its formation near the surface. Through the study found that the endoplasmic reticulum and golgi apparatushe are the two organelles which is sensitive to heavy metals in the cell, Jiang, etc With a certain concentration of Cd2+ processing garlic root tip cells, the cells was observed within the golgi apparatus and endoplasmic reticulum[24]. Heavy metal stress, therefore, can make the plant cell in the body of the ribosome, endoplasmic reticulum and golgi apparatus in expansion, turbidity, the phenomenon such as collapse, will affect its corresponding biological function.

4 Conclusion

Toxic effect of heavy metals in plants is not only a single organ, but the plant cell membrane structure and the membrane structure, biochemical and physiological activities of the overall damage, Under normal circumstances, the plant for low

concentration of heavy metal stress through its cell wall fixed, and the roles of the choice of plasma membrane permeability and vacuole area room effect can produce certain ability to resist, but when the heavy metal stress exceeds a certain threshold, then will be on the plant cell ultrastructure damage, thus affect its biological function. Different plant species utilize different strategies to cope with heavy metal toxicity, ranging from sensitivity to tolerance and heavy metal accumulation. Cadmium minimization must be an important demand,so that are beneficial to plants and human survival.

篇四：GMAT阅读解析 by 申友Alice

专业GMAT与托福保分机构 每周一篇

By 申友Alice老师 All the cells in a particular plant start out with the same complement of genes. How then can these cells differentiate and form structures as different as roots, stems, leaves, and fruits? // (提出现象一组基因中产生的细胞形成不同的根茎叶结构。) The answer is that only a small subset of the genes in a particular kind of cell are expressed, or turned on, at a given time. This is accomplished by a complex system of chemical messengers that in plants include hormones and other regulatory molecules. Five major hormones have been identified: auxin, abscisic acid, cytokinin, ethylene, and gibberellin. Studies of plants have now identified a new class of regulatory molecules called oligosaccharins.（专有名词第一次出现需引起重视，生词可用首字母代入法表示。） // (解释现象，只有一部分基因通过五大荷尔蒙和OL物质被表达出来。) //

Unlike（出现比较词，注意对比的双方）the oligosaccharins, the five well-known that is, // are not very usefulfor instance句总结句。） stimulates the rate of cell elongation, causes shoots to grow up and roots to grow down, and inhibits the growth of lateral shoots. Auxin also causes the plant to develop a vascular system, to form lateral roots, and to produce ethylene.（五大荷尔蒙因为具有多效性所以在控制植物生长方面不是很有作用。）//

The pleiotropy of the five well-studied plant hormones is somewhat analogous to that of certain hormones in animals. For example, （举例略读）hormones from the hypothalamus in the brain stimulate the anterior lobe of the pituitary gland to synthesize and release many different hormones, one of which stimulates the release of hormones from the adrenal cortex. // (植物中五大荷尔蒙的多效性和动物相似。) These hormones have specific effects on target organs all over the body. One hormone stimulates the thyroid gland, for example, another the ovarian follicle cells, and so forth. In other words, there is a hierarchy of hormones.(注意第一次出现hierarchy, 与下段开头照应。) //（五大荷尔蒙的专一性体现在动物目标器官上。）

Such a hierarchy may also exist in plants. // (分级系统也出现在植物中。) Oligosaccharins are fragments of the cell wall released by enzymes: different enzymes release different oligosaccharins. There are indications that pleiotropic plant hormones may actually function by activating the enzymes that release these other,

专业GMAT与托福保分机构 more specific chemical messengers from the cell wall. // （具体说明植物中的分级系统，荷尔蒙释放酶，酶释放OL物质。）

逻辑简图：

文章属于自然科学类题材，写作结构为现象解释型。

第一段：

第一层：提出现象，一组相同的基因产生出的细胞形成不同的组织结构，如根茎叶。

第二层：解释现象，因为只有一部分的基因被表达了，并且是通过五大荷尔蒙和OL物质表达的。

第二段：

第一层：五大荷尔蒙与OL物质不同，具有多效性。

第二层：五大荷尔蒙因为具有多效性，而在控制植物生长方面不是很有效。

第三段：

第一层：五大荷尔蒙在植物中的多效性和动物中相似。

第二层：五大荷尔蒙的专一性体现在动物的目标器官中。

第四段：

第一层：分级系统也出现在植物中。

第二层：植物中的分级系统表现为荷尔蒙释放酶，酶释放OL物质。

are not useful in controlling the growth of crops（细节题：定位到第二段的第二层）

错误表述

(B) 同义转换，正确

(C) none of the hormones can function without the others 新说法

(D) each hormone has different effects on different kinds of plants 新说法

(E) each hormone works on only a small subset of a cell’s genes at any particular time 段落定位混淆

2. The passage suggests that the place of hypothalamic hormones in the hormonal hierarchies of animals is similar to the place of which of the following in plants?（细节题之推论题：定位到第三段的第一层）

(A) Plant cell walls

(B) The complement of genes in each plant cell

(C) A subset of a plant cell’s gene complement

(D) The five major hormones

(E) The oligosaccharins

3. The passage suggests that which of the following is a function likely to be

performed by an oligosaccharin? （细节题：注意用OL物质定位，原文中分别有三处提到了OL物质-第一段（第二层）；第二段（第一层）；第四段（第二层））

(A) To stimulate a particular plant cell to become part of a plant’s root system 对应

第一段的信息

专业GMAT与托福保分机构

(B) To stimulate the walls of a particular cell to produce other oligosaccharins 新说法

(C) To activate enzymes that release specific chemical messengers from plant cell walls. 错误表述

(D) To duplicate the gene complement in a particular plant cell. 新说法

(E) To produce multiple effects on a particular subsystem of plant cells. 错误表述

4. The author mentions specific effects that auxin has on plant development in order to illustrate the （细节题：定位到第二段的第二层；举例中的信息，注意例子前的总结句。）

(A) point that some of the effects of plant hormones can be harmful. 新说法

(B) way in which hormones are produced by plants. 新说法

(C) hierarchical nature of the functioning of plant hormones. 段落定位混淆

(D) differences among the best-known plant hormones. 新说法

(E) concept of pleiotropy as it is exhibited by plant hormones. 例子前的总结句

5. According to the passage, which of the following best describes a function performed by oligosaccharins? （细节题：注意用OL物质定位，原文中分别有三处提到了OL物质-第一段（第二层）；第二段（第一层）；第四段（第二层））

(A) Regulating the daily functioning of a plant’s cells 新说法

新说法

错误表述

错误表述(E) cells’ genes 对应第一段信息

6. The passage suggests that, unlike the pleiotropic hormones, oligosaccharins could be used effectively to （细节题：定位到第二段的第一层。）

(A) trace the passage of chemicals through the walls of cells 新说法

(B) pinpoint functions of other plant hormones 新说法

(C) artificially control specific aspects of the development of crops 对应第二段的信息

(D) alter the complement of genes in the cells of plants 新说法

(E) alter the effects of the five major hormones on plant development 新说法

篇五：英语阅读理解

Ⅱ．完形填空(共15小题；每小题l分，满分l5分)

阅读下面短文，掌握其大意，然后从各题所给的四个选项中选出一个最佳答案。

On my first job, I worked as a sports editor for a small

there was an envelope on my desk one morning. From the

When I opened it, I found a note and it read, “You did a good

job. Go on!”

was a green hand（新手）kept the note in my desk drawer. Whenever I doubted

again. Later, when I made friends with Mr John, the note writer, I learned that he often wrote notes young people in many fields. “feel happy,” he told me, “I feel happy, too.”

, many people to .

So, when you find some people around you , please write a note of ,but remember Mr John's words—making others feel happy makes you happy, too.

16. A. certain B. sure C. surprised D. frightened

17. A. calendar B. envelope C. book D. photo

18. A. signed B. picked C. copied D. practised

19. A. unhappy B. sleepy C. excited D. sad

20. A. why B. that C. what D. whether

21. A. serious B. confident C. strict D. humorous

22. A. expect B. describe C. introduce D. encourage

23. A. other B. the other C. others D. the others

24. A. But B. However C. Therefore D. Actually

25. A. opinion B. advice C. idea D. decision

26. A. stronger B. weaker C. harder D. easier

27. A. wait B. last C. stop D. rest

28. A. once B. only once C. more than once D. less than once

29. A. thanks B. truth C. trouble D. help

30. A. happen B. matter C. turn D. hold

Ⅲ．阅读理解(共15小题；A、B两篇每小题2分，C篇每小题l分，满分25分)

阅读下文，从所给的四个选项中选出一个最佳答案。

A

A little girl walked to and from school every day. Though it was not

fine and clouds appeared in the sky that morning, the little girl made her

daily trip to school as usual. When school was over, winds became stronger

and it began to rain.

The mother of the little girl felt worried that her daughter would be afraid when she walked home from school and that lightning might frighten her child. Following the bright light of lightning, the mother quickly got into her car and drove to her child's school.

As the mother drove along the road, she saw her little girl walking alone in the rain. To her great surprise, she found that when a lightning came, her daughter stopped, looked up and smiled. Another lightning came and then another followed. With each lightning, the little girl stopped, looked up and smiled.

Inside the car, the mother asked her daughter, "What were you doing? Why did you look up and smile when the lightning came?" The little girl answered with a smile, “ Mum, you know, God was looking at me. Each time I felt a little afraid walking in the rain, God would take a picture of me. I knew he was playing a game with me.”

31. How did the little girl go to school every day?

A. By car. B. On foot. C. By bus. D. By bike.

32. What was the weather like that day?

A. It was rainy. B. It was fine.

C. It was just windy. D. It was only cloudy.

.

A. she couldn't help her daughter

B. her daughter hadn't taken her umbrella

C. she had something more important to do

D. her daughter might be afraid of the lightning

A. proud B. shy C. brave D. nervous

A. a menu B. a magazine C. a dictionary D. a report

B

The spring festival is celebrated not only in Chipa but also in other parts of the world. The traditional holiday is the most important to Chinese both home and abroad.

United Kingdom

Celebrations for Spring Festival in the UK started in 1980, with the first evening party held in 2002. Every new year, people get together and have a lot of activities. They sing songs, dance to music, share photos with friends or enjoy films in a cinema.

United States

Spring Festival has become a key time for Chinese living or working in the US. They join in a large evening party to welcome the traditional new year. It is a good chance for people to build a circle of friends and feel that they are not alone because they share the same culture and values.

Australia

The Chinese new year will be welcomed with three weeks of celebrations across Australia. Many people come to Sydney's Chinatown or Little Bourke in Melbourne. They enjoy fireworks, lion dances, dragon boat races and many other traditional activities. The celebrations are also a bridge towards better understanding between Chinese and non-Chinese.

Singapore

The family dinner on new year's eve is an important tradition for Chinese whether they

were born in Singapore or moved there from China. They place traditional food on a table as an act of remembering their past. Then the whole family enjoy their dinner together. They usually hold it at home because having it in a restaurant takes away the meaning of the tradition.

.

A, 1890 B. 1980 C. 2000 D. 2002

A, say hello to the new year B. refuse a good chance

C. tell others they are alone D. share different cultures

38. Chinese in Australia enjoy the following activities except.

A, fireworks B. lion dances

C. bridges D. dragon boat races

39. In Singapore, Chinese families don't hold the new year dinner at a restaurant but at

A, they were born in Singapore B. they moved there from other places

C. the restaurant is far away D. they want to keep Chinese tradition

.

A. all parts of the world celebrate Spring Festival

B. the Chinese new year is celebrated only in China

C. celebrations for Spring Festival are just held in four foreign countries

D, Chinese across the world have a strong feeling towards Spring Festival

C

It may seem easy to say that plants and animals are

different. Any child can tell the difference between a tree and

a dog. But those differences are far deeper than just what they

look like. The cells（细胞） that plants are made up of are

different. In other words, the cell wail of plants has something

special.

First of all, it's important to find that not all plant cells

have a cell wall. Besides, there are many differences of a cell

wall based on the kinds of plant. The following is meant to be what a plant cell wall is like.

The cell wall of a plant is on the outside of the cell membrane(膜). It is usually hard and cannot be easily, but the degree of flexibility(韧性) of the cell wall is different. It is based on the special use that the cell has in keeping the plant alive. Cells that make up the trunk of a tree are clearly less flexible than cells on a leaf.

Cell wails act in many ways. They serve to protect the plant. They provide support, as well as help in the movement of chemicals and wastes into and out of the cell. More importantly, they control the water that goes in and out. Plants must have good water controlling systems(系统), allowing them to keep water during dry seasons, and get rid of unnecessary water. Plants can't walk around to find water, so being able to control water is very important.

So there you have it —what a plant cell wall is. Of course, there are many other things that are not talked about here. Knowing more about plant cell wails requires further study and research.

A. Different Plants B. Different Animals

C. The Plant Cell Wall D. The Uses of Cells

A. all plants have a ceil wall

B. plant cells and animal cells are the same

C. different kinds of plant have different cell walls

D. there are no differences between the cells of a tree and a dog

43. The underlined word A. shape-changed B. water-kept C. sun-burnt D. skin-broken

A. as flexible as B. not so flexible as

C. more important than D. less important than

45. What is the most important use of a plant cell wall?

A. To protect the plant. B. To provide support.

C. To move chemicals and wastes. D. To control the water.

Ⅵ．任务型阅读(共l0小题；每小题2分，满分20分)

阅读下面短文，根据要求完成下列各题。

A

As the summer of 2012 draws near, there will be more and

more reports about the London Olympic Games. Sportsmen and

visitors from all over the world will travel to London.With different

people to come from different cultures, speaking different

languages is a difficult job for the host city. In the near

future,London will have a chance to turn into a multilingual(多语

的) city.

Languages will play an important part in the Olympics. The need for languages is present in different sides of the games. London wii1 be home to a large multicultural population with more than 300 languages to be spoken in the city. Chances will come for businesses of all sizes to make money by dealing with the visitors from all over the world.To be able to use the good chances, businesses need to pay attention to language services.

Language services will be very important for helping people to communicate during the games. Communicating with people in their own language has already been one of the key purposes. To meet the need of the coming games, Londoners are asked to study more languages through short time educational programs while they are preparing for the games.Language services should be prepared months before the start to solve any language problems that might come up during the games. To get the best possible results, translation work should also be carried out months ahead so that language services are ready for future visitors.

21. When will the London Olympics be held?

22. Are languages important in the Olympics?

23. What do businesses need to do if they want to use the good chances?

24. How will Londoners study more languages?

25. What should be done to get the best possible results?

五、阅读填词（共10小题，每小题1分，满分10分）注意：每空限填一个单词

阅读短文，根据所读内容在短文后图表中的空格里填入一个恰当的单词。

Some people believe that your nationality can influence your personality. This is why you might hear someone saying “She is a typical(典型的) Australian” or “He is so French”. It seems that people from a certain country share certain similar characteristics.

French French people are often seen as romantic and outgoing people with a great love for life, food and wine. They are good at singing and dancing.

Chinese

Chinese are friendly people who are hard-working. They are polite because they are careful about “saving face” when dealing with other people.

Australians

Australians are merry people who spend a lot of time outdoors. They enjoy a slower life. They laugh a lot but sometimes people think they are loud and rude.

Germans Germans are often described as being serious and careful. They are hard workers and pay a lot of attention to details. However, sometimes people say Germans have no sense of humour.

All these national types can be true for some people, but very wrong for others. For example, you might meet a German who is a confident singer with a great sense of humour, or an Australian who is shy and quiet.!

根据短文内容，从各题所给的A、B、C、D四个选项中选出最佳选项。

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