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Plant disease

Economically, one of the most important areas of research in environmental physiology is that of phytopathology, the study of diseases in plants and the manner in which plants resist or cope with infection. Plant are susceptible to the same kinds of disease organisms as animals, including viruses, bacteria, and fungi, as well as physical invasion by insects and roundworms.

Because the biology of plants differs with animals, their symptoms and responses are quite different. In some cases, a plant can simply shed infected leaves or flowers to prevent the spread of disease, in a process called abscission. Most animals do not have this option as a means of controlling disease. Plant diseases organisms themselves also differ from those causing disease in animals because plants cannot usually spread infection through casual physical contact. Plant pathogens tend to spread via spores or are carried by animal vectors.

One of the most important advances in the control of plant disease was the discovery of Bordeaux mixture in the nineteenth century. The mixture is the first known fungicide and is a combination of copper sulfate and lime. Application of the mixture served to inhibit the growth of downy mildew that threatened to seriously damage the French wine industry.[7]

Sir Francis Bacon published one of the first plant physiology experiments in 1627 in the book, Sylva Sylvarum. Bacon grew several terrestrial plants, including a rose, in water and concluded that soil was only needed to keep the plant upright. Jan Baptist van Helmont published what is considered the first quantitative experiment in plant physiology in 1648. He grew a willow tree for five years in a pot containing 200 pounds of oven-dry soil. The soil lost just two ounces of dry weight and van Helmont concluded that plants get all their weight from water, not soil. In 1699, John Woodward published experiments on growth of spearmint in different sources of water. He found that plants grew much better in water with كشف تسربات المياه soil added than in distilled water.

Stephen Hales is considered the Father of Plant Physiology for the many experiments in the 1727 book;[8] though Julius von Sachs unified the pieces of plant physiology and put them together as a discipline. His Lehrbuch der Botanik was the plant physiology bible of its time.[9]

Researchers discovered in the 1800s that plants absorb essential mineral nutrients as inorganic ions in water. In natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth. When the mineral nutrients in the soil are dissolved in water, plant roots absorb nutrients readily, soil is no longer required for the plant to thrive. This observation is the basis for hydroponics, the growing of plants in a water solution rather than soil, which has become a standard technique in biological research, teaching lab exercises, crop production and as a hobb

The flower, which is one of the defining features of angiosperms, is essentially a stem, whose leaf primordia become specialised, following which the apical meristem stops growing, a determinate growth pattern, in contrast to vegetative stems.[1][6] The flower stem is known as a pedicel, and those flowers with a stalk are called pedicellate, while those without are called sessile.[7] In the angiosperms, the flowers are arranged on a flower stem as an inflorescence, though these structures are very different in gymnosperms and angiosperms, which are dealt with in more detail here. Just beneath (subtended) the flower there may be a modified and usually reduced leaf, called a bract. A secondary smaller bract is a bracteole (bractlet, prophyll, prophyllum), often on the side of the pedicel, and generally paired. A series of bracts subtending the calyx (see below) is an epicalyx.[7]

In angiosperms, the specialised leaves that play a part in reproduction are arranged around the stem in an ordered fashion, from the base to the apex of the flower. The floral parts are arranged at the end of a stem without any internodes, the receptacle (also called the floral axis, or thalamus) which is generally very small. Some flower parts are solitary, while others may form a tight spiral or whorl, around the flower stem. First, at the base, are those non-reproductive structures involved in protecting the flower when it is still a bud, the sepals, then those parts that play a role in attracting pollinators and are typically coloured, the petals, which together with the sepals make up the perianth (perigon, perigonium). If the perianth is not differentiated into sepals and petals, they are collectively known as tepals. If the perianth is differentiated كشف تسربات المياه بالرياض , the outer whorl of sepals forms the calyx, and the inner whorl of petals, the corolla. In some flowers, a tube or cup like hypanthium (floral tube) is formed above or around the ovary and bears the sepals, petals and stamens. There may also be a nectary producing nectar. Nectaries may develop on or in the perianth, receptacle, androecium (stamens), or gynoecium. In some flowers nectar may be produced on nectariferous disks. Disks may arise from the receptable and are doughnut or disk shaped. They may also surround the stamens (extrastaminal), be at their bases (staminal)  شركة كشف تسربات المياه بالرياض or be inside the stamina (intrastaminal).[8]

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Plant physiology

Plant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants.[1] ...

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