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A herbaceous plant (in botanical use simply herb) is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground. Herbaceous plants may be annuals, biennials or perennials.
Annual herbaceous plants die completely at the end of the growing season or when they have flowered and fruited, and they then grow again from seed.
Herbaceous perennial and biennial plants have stems that die at the end of the growing season, but parts of the plant survive under or close to the ground from season to season (for biennials, until the next growing season, when they flower and die). New growth develops from living tissues remaining on or under the ground, including roots, a caudex (a thickened portion of the stem at ground level) or various types of underground stems, such as bulbs, corms, stolons, rhizomes and tubers. Examples of herbaceous biennials include carrot, parsnip and common ragwort; herbaceous perennials include peony, hosta, mint, most ferns and most grasses. By contrast, non-herbaceous perennial plants are woody plants which have stems above ground that remain alive during the dormant season and grow shoots the next year from the above-ground parts – these include trees, shrubs and vines.
Some relatively fast-growing herbaceous plants (especially annuals) are pioneers, or early-successional species. Others form the main vegetation of many stable habitats, occurring for example in the ground layer of forests, or in naturally open habitats such as meadow, salt marsh or desert.
Plant pathology (also phytopathology) is the scientific study of plant diseases caused by pathogens (infectious diseases) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like organisms, phytoplasmas, protozoa, nematodes and parasitic plants. Not included are ectoparasites like insects, mites, vertebrate or other pests that affect plant health by consumption of plant tissues. Plant pathology also involves the study of pathogen identification, disease etiology, disease cycles, economic impact, plant disease epidemiology, plant disease resistance, how plant diseases affect humans and animals, pathosystem genetics, and management of plant diseases.
The fungi reproduce both sexually and asexually via the production of spores. These spores may be spread long distances by air or water, or they may be soil borne. Many soil borne spores, normally zoospores, are capable of living saprotrophically, carrying out the first part of their lifecycle in the soil.
Biotrophic fungal pathogens colonize living plant tissue and obtain nutrients from living host cells. Necrotrophic fungal pathogens infect and kill host tissue and extract nutrients from the dead host cells. See Powdery Mildew and Rice Blast images below.
Significant fungal plant pathogens include:
- Fusariumspp. (causal agents of Fusarium wilt disease)
- Thielaviopsisspp. (causal agents of: canker rot, black root rot, Thielaviopsis root rot)
- Magnaporthe grisea(causal agent of blast of rice and gray leaf spot in turfgrasses)
- Phakospora pachyrhizi(causal agent of soybean rust)
- Pucciniaspp. (causal agents of severe rusts of virtually all cereal grains and cultivated grasses)
The oomycetes are not true fungi but are fungal-like organisms. They include some of the most destructive plant pathogens including the genusPhytophthora which includes the causal agents of potato late blight and sudden oak death.
Despite not being closely related to the fungi, the oomycetes have developed very similar infection strategies and so many plant pathologists group them with fungal pathogens.
Significant oomycete plant pathogens
Most bacteria that are associated with plants are actually saprotrophic, and do no harm to the plant itself. However, a small number, around 100 species, are able to cause disease. Bacterial diseases are much more prevalent in sub-tropical and tropical regions of the world.
Most plant pathogenic bacteria are rod shaped (bacilli). In order to be able to colonize the plant they have specific pathogenicity factors. Five main types of bacterial pathogenicity factors are known:
2. ToxinsThese can be non-host specific, and damage all plants, or host specific and only cause damage on a host plant.
3. Effector proteins These can be secreted into the extracellular environment or directly into the host cell, often via the Type three secretion system. Some effectors are known to suppress host defense processes.
Answers:Funny you mentioned this. My cousin in the Philippines had this tree, whose limb fell because of a storm. It was completely separated from the limb, but it laid on the ground continuing to bear fruits. It did that bearing fruits until it finally died a slow death, 8-10 years later. It wasn't connected to the mother tree, but it was next to it. My dad also had an apple tree, that got too heavy of fruits, so he tied the branches together to keep it from falling, it was starting to break off, and it made the tree live. If it's hardwood, it can live & survive, by tying the branches together, but if it's soft wood, just cut it off and it will sprout new branches.
Answers:Bezzy ROOT SYSTEM The root system is generally underground. It is non green brown and positively geotropic. In dicotyledonous plants the root system is a tap root system that consists of a tap root, lateral roots, roots lets and root hairs. The tap root is the main root that grows vertically downwards into the soil. The lateral roots develop upon the tap root which bear root lets and root hairs. The tip of the tap root and its branches have root cap at their tips. Fibrous root system is present in monocotyledonous plants. It consist along, equally strong adventitious roots developed from the base of the stem. The main functions of root system are: 1. Fixation of the plant in the soil. 2. Absorption of mineral water from the soil. 3. Conduction of water to shoot system. SHOOT SYSTEM The shoot system is the aerial, green coloured positively phototropic (negatively geotropic) part of the plant. The central axis of the shoot system is called stem. The stem bears branches, leaves, buds flowers etc. The stem shows the differentiation of nodes and internodes. The place where the leaf develops on the stem is called the node. The portion of the stem between two successive nodes is called the internode. The angle between the stem and upper part of the leaf is called axil. The main stem and its branches end with apical buds or terminals buds. The apical bud helps in the vertical growth of the stem. The buds that are present in the axils of leaves are called axillary buds. The axillary buds normally develop into lateral branches or inflorescence. The leaves and flowers are the two important appendages of the shoot system. LEAF The leaf is a flat green, vegetable appendage. It is exogenous in origin. Usually the leaf bears a leaf base petiole and the lamina. The thin expanded part of the leaf is called the lamina. It has definite shape, apex and margin. The lamina shows a mid rib bearing veins and veinlets. In monocots and the veins show parallel arrangement and in dicots they are reticulately arranged. The chief functions of the leaf are: 1. Manufacture of organic food materials by photosynthesis. 2. Removal of excess of water by transpiration. FLOWER The flower is the reproductive organ of a plant. Flower may be axillary or terminal in position. The develop singly or in the clusters. The stalk of the flower is called pedicel. It ends with thalamus. Upon the thalamus floral organs are present in whorls. Calyx and Corolla are the non essential organs of the flower. Androecium and gynoecium are the essential organs. After pollination and fertilization the flowers produce fruit which contain seeds. The fruits and the seeds are the products of sexual reproduction. The seeds on germination develop into plants. The chief functions of the flower is to carry out sexual reproduction. I think thats what you asked for. Check in http://bisbio.in
Answers:I wouldn't exactly say that light causes a plant to grow more slowly, just not as tall. It might be more accurate to say that lack of light makes plants grow taller. Think of it in terms of evolution, of survival. If a plant is not getting enough light, then growing taller will likely increase its chances of getting more. So, if a plant is getting enough light, it does not need to expend the extra energy to grow taller. So it has more energy to expend on making seeds, for example. The mechanism that makes it grow taller in inadequate light has survived because such plants will be more successful - and produce more offspring. Which is what it's all about.
Answers:Perennials can be herbaceous and die down to their crown during their dormant period or they can be woody and retain a large exposed structure even while dormant. The function of the stems in both cases is to provide vertical space to transport water & sap via vascular tissues to the transpiring photosynthetic organs (leaves) and the reproductive organs (cones or flowers) from the foraging roots. Woody stems often have the additional function of spatial array. They have a branching pattern in order to display their leaves over as dispersed a space as possible in order to maximized their exposure to sunlight while minimizing water loss. Stems provide height and spread so plants can seek sunlight more efficiently without shading out their own lower leaves. Herbaceous or deciduous perennials that die down each year are mint, peony, hosta, iris, and most grasses. Woody herbaceous herbs are thyme, sage, rosemary and lavender. Shrubs like oleander or rhododendron, plus palms, cactus, rattan, or bamboo are all woody perennials.