Plant and Dia
施工组织设计范本 Plants make up the majority of the earth's living environment as trees，grass,flowers,and so on. Directly or indirectly，plants also make up all the food on which humans and all animals depend。 Even the meat，milk，and eggs that we and other carnivores eat come from animals that depend on plants for their food。 Plants are the only higher organisms that can convert the energy of sunlight into stored，usable chemical energy in carbohydrates，proteins，and fats。 All animals，including humans，depend on the plant substances for survival.
Plants, whether cultivated or wild，grow and produce well as long as the soil provides them with sufficient nutrients and moisture，sufficient light reaches their leaves，and the temperature remains within a certain "normal”range。 Plants，however，also get sick。 Sick plants grow and produce poorly, they exhibit various type of symptoms，and often parts of plants or whole plants die. It is not known whether diad plants feel pain or discomfort。
宫保鸡丁的步骤 The agents that cau dia in plants are the same or very similar to tho causing dia in human， and animals. They include pathogenic microorganisms, such as virus, bacteria，fungi,protozoa，and nematodes,and unfavorable environmental conditions，such as lack or excess of nutrients，moisture,and light，and the prence of toxic chemicals in air or soil。 Plants also suffer from competition with other，unwanted plants(weeds），and，of cour they are often damaged by attacks of incts。 Plant damage caud by incts，humans,or other animals is not usually included in the study of plant pathology.
Plant pathology is the study of the organisms and of the environmental factors that cau dia in plants; of the mechanisms by which the factors induce dia in plants；and of he methods of preventing or controlling diad reducing the damage it caus. Plant pathology is for plants largely what medicine is for humans and veterinary medicine is for animals。 Each discipline studies the caus,mechanisms,and control of dias affecting the organisms with which it deals，i. e.,plants，humans，and animals, respectively。
吹箫
Plant pathology is an integrative science and profession that us and combines the basic knowledge of botany，mycology,bacteriology，virology，nematology，plant anatomy，plant physiology，genetics，molecular biology and genetic engineering，biochemistry，horticulture，agronomy,tissue culture，soil science,forestry,chemistry，physics，meteorology，and many other branches of science. Plant pathology profits from advances in any one of theJJG196 sciences,and many advances in other sciences have been made in attempts to solve plant pathological problems:
As a science，plant pathology tries to increa our knowledge about plant dias。 At the same time，plant pathology tries to develop methods， equipment，and materials through which plant dia can be avoided or controlled。 Uncontrolled plant dia may result in less food and higher food prices or in food of poor quality。 Diad plant product may sometimes be 悴怎么组词poisonous and unfit for consumption. Some plant dias may wipe out entire 风吹的图片plant species and many affect the beauty and landscape of our environment。 Controlling plant dia results in more food of better quality and a more aesthetically pleasing environment，but consumers must pay for costs of materials,equip
ment, and labor ud to control plant dias and,sometimes,for other less evident costs such as contamination of the environment。
In the last 100 years，the control of plant dias and other plant pests has depended increasingly on the extensive u of toxic chemicals（pesticides)． Controlling plant dias often necessitates the application of such toxic chemicals not only on plants and plant produce that we consume，but also into the soil，where many pathogenic microorganisms live and attack the plant roots。 Many of the chemicals have been shown to be toxic to nontarget长城的历史背景 microorganisms and animals and may be toxic to humans。 The short-and long—term costs of environmental contamination on human health and welfare caud by our efforts to control plant dias(and other pests）are difficult to estimate. Much of modern rearch in plant pathology aims at finding other environmentally friendly means of controlling plant dias. The most promising approaches include conventional breeding and genetic engineering of dia-resistant plants,application of dia—suppression cultural practices，RNA—and gene—silencing techniques，of plant defen—promoting nontoxic substances，and，to some
extent,u of biological agents antagonistic to the microorganisms that cau plant dia.
The challenges for plant pathology are to reduce food loss while improving food quality and,at the same time,safeguarding our environment。 As the world population continues to increa while arable land and most other natural resources continue to decrea，and as our environment becomes further congested and stresd，the need for controlling plant dia effectively and safely will become one of the most basic necessities for feeding the hungry billions of our increasingly overpopulated world.
Becau it is not known whether plants feel pain or discomfort and becau,in any ca，plants do not speak or otherwi communicate with us，it is difficult to pinpoint exactly when a plant is diad。 It is accepted that a plant is healthy，or normal，when it can carry out its physiological functions to the best of its genetic potential。 The meristematic（cambium） cells of a healthy plant divide and differentiate as needed，and different types of specialized cells absorb water and nutrients from the soil；transloc
速溶咖啡品牌ate the to all plant parts； carry on photosynthesis，translocate，metabolize,or store the photosynthetic products;and produce ed or other reproductive organs for survival and multiplication. When the ability of the cells of a plant or plant part to carry out one or more of the esntial functions is interfered with by either a pathogenic organism or an adver environmental factor，the activities of the cells are disrupted,altered,or inhibited，the cells malfunction or die，and the plant becomes diad。 At first，the affliction is localized to one or a few cells and is invisible. Soon,however,the reaction becomes more widespread and affected plant parts develop changes visible to the naked eye. The visible changes are the symptoms of the dia。 The visible or otherwi measurable adver changes in a plant,produced in reaction to infection by an organism or to an unfavorable environmental factor，are a measure of the amount of dia in the plant. Dia in plants,then,can be defined as the ries of invisible and visible respons of plant cells and tissues to a pathogenic organism or environmental factors that result in adver changes in the form，function，or integrity of the plant and may lead to partial impairment or death of plant parts or of the entire plant.
