|
Guttation 088 Cropped
Guttation is the exudation of drops of xylem sap on the tips or edges of leaves of some vascular plants, such as grasses, and a number of fungi, which are not plants but were previously categorized as such and studied as part of botany. Guttation (from Latin ''gutta'' drop) is not to be confused with dew, which condenses from the atmosphere onto the plant or fungus surface and does not originate from within them. Guttation generally happens at night. Process At night, transpiration usually does not occur, because most plants have their stomata closed. When there is a high soil moisture level, water will enter plant roots, because the water potential of the roots is lower than in the soil solution. The water will accumulate in the plant, creating a slight root pressure. The root pressure forces some water to exude through special leaf tip or edge structures, hydathodes or water glands, forming drops. Root pressure provides the impetus for this flow, rather than transpirational ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dew On An Equisetum Fluviatile Luc Viatour
Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening due to condensation. As the exposed surface cools by radiating its heat, atmospheric moisture condenses at a rate greater than that at which it can evaporate, resulting in the formation of water droplets. When temperatures are low enough, dew takes the form of ice, called frost. Because dew is related to the temperature of surfaces, in late summer it forms most easily on surfaces that are not warmed by conducted heat from deep ground, such as grass, leaves, railings, car roofs, and bridges. Formation Water vapor will condense into droplets depending on the temperature. The temperature at which droplets form is called the ''dew point''. When surface temperature drops, eventually reaching the dew point, atmospheric water vapor condenses to form small droplets on the surface. This process distinguishes dew from those hydrometeors (meteorological occurrences of water), wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water Potential
Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure and matrix effects such as capillary action (which is caused by surface tension). The concept of water potential has proved useful in understanding and computing water movement within plants, animals, and soil. Water potential is typically expressed in potential energy per unit volume and very often is represented by the Greek letter ψ. Water potential integrates a variety of different potential drivers of water movement, which may operate in the same or different directions. Within complex biological systems, many potential factors may be operating simultaneously. For example, the addition of solutes lowers the potential (negative vector), while an increase in pressure increases the potential (positive vector). If the flow is not restricte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osmosis
Osmosis (, ) is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential (region of higher solute concentration), in the direction that tends to equalize the solute concentrations on the two sides. It may also be used to describe a physical process in which any solvent moves across a selectively permeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations. Osmosis can be made to do work. Osmotic pressure is defined as the external pressure required to be applied so that there is no net movement of solvent across the membrane. Osmotic pressure is a colligative property, meaning that the osmotic pressure depends on the molar concentration of the solute but not on its identity. Osmosis is a vital process in biological systems, as biological membranes are semiperm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homeostasis
In biology, homeostasis (British English, British also homoeostasis) Help:IPA/English, (/hɒmɪə(ʊ)ˈsteɪsɪs/) is the state of steady internal, physics, physical, and chemistry, chemical conditions maintained by organism, living systems. This is the condition of optimal functioning for the organism and includes many variables, such as body temperature and fluid balance, being kept within certain pre-set limits (homeostatic range). Other variables include the pH of extracellular fluid, the concentrations of sodium, potassium and calcium ions, as well as that of the blood sugar level, and these need to be regulated despite changes in the environment, diet, or level of activity. Each of these variables is controlled by one or more regulators or homeostatic mechanisms, which together maintain life. Homeostasis is brought about by a natural resistance to change when already in the optimal conditions, and equilibrium is maintained by many regulatory mechanisms: it is thought to be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fertilizer Burn
Fertilizer burns occur when the use of too much fertilizer, the wrong type of fertilizer, or too little water with a fertilizer causes damage to a plant. Although fertilizer is used to help a plant grow by providing nutrients, too much will result in excess salt, nitrogen, or ammonia which have adverse effects on a plant. An excess of these nutrients can damage the plant's ability to photosynthesize and cellularly respire, causing visible burns. The intensity of burns determine the strategy for recovery. Background Fertilizers contain nutrients that increase plant growth by increasing the rate of photosynthesis (the process in which plants uptake water and nutrients to create sugar) and cellular respiration (the process in which carbon dioxide and sugar is broken down to be used as energy, releasing oxygen). Nutrients and water enter the plant through the plants’ root cell membranes (the barrier separating the inside of the root cells from the outside) via of osmosis (the movem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colony Collapse Disorder
Colony collapse disorder (CCD) is an abnormal phenomenon that occurs when the majority of worker bees in a honey bee colony disappear, leaving behind a queen, plenty of food, and a few nurse bees to care for the remaining immature bees. While such disappearances have occurred sporadically throughout the history of apiculture, and have been known by various names (including disappearing disease, spring dwindle, May disease, autumn collapse, and fall dwindle disease), the syndrome was renamed colony collapse disorder in early 2007 in conjunction with a drastic rise in reports of disappearances of western honey bee (''Apis mellifera'') colonies in North America. Beekeepers in most European countries had observed a similar phenomenon since 1998, especially in Southern and Western Europe; the Northern Ireland Assembly received reports of a decline greater than 50%. The phenomenon became more global when it affected some Asian and African countries as well. Colony collapse disorder co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Imidacloprid
Imidacloprid is a systemic insecticide belonging to a class of chemicals called the neonicotinoids which act on the central nervous system of insects. The chemical works by interfering with the transmission of stimuli in the insect nervous system. Specifically, it causes a blockage of the nicotinergic neuronal pathway. By blocking nicotinic acetylcholine receptors, imidacloprid prevents acetylcholine from transmitting impulses between nerves, resulting in the insect's paralysis and eventual death. It is effective on contact and via stomach action. Because imidacloprid binds much more strongly to insect neuron receptors than to mammal neuron receptors, this insecticide is more toxic to insects than to mammals. From 1999 through , imidacloprid was the most widely used insecticide in the world. Although it is now off patent, the primary manufacturer of this chemical is Bayer CropScience (part of Bayer AG). It is sold under many names for many uses; it can be applied by soil injection ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neonicotinoid
Neonicotinoids (sometimes shortened to neonics ) are a class of neuro-active insecticides chemically similar to nicotine, developed by scientists at Shell and Bayer in the 1980s. The neonicotinoid family includes acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, nithiazine, thiacloprid and thiamethoxam. Imidacloprid has been the most widely used insecticide in the world from 1999 through . Compared to organophosphate and carbamate insecticides, neonicotinoids are less toxic to birds and mammals. Neonicotinoid use has been studied in relation to adverse ecological effects, including honey-bee colony collapse disorder (CCD), and declining populations of insect-eating birds. In 2013, the European Union and some neighbouring countries restricted the use of certain neonicotinoids. In 2018 the EU banned the three main neonicotinoids (clothianidin, imidacloprid and thiamethoxam) for all outdoor uses, but in 2020, France re-allowed the use of neonicotinoids on sugar beet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transpirational Pull
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from the Ancient Greek word (''xylon''), meaning "wood"; the best-known xylem tissue is wood, though it is found throughout a plant. The term was introduced by Carl Nägeli in 1858. Structure The most distinctive xylem cells are the long tracheary elements that transport water. Tracheids and vessel elements are distinguished by their shape; vessel elements are shorter, and are connected together into long tubes that are called ''vessels''. Xylem also contains two other type of cells: parenchyma and fibers. Xylem can be found: * in vascular bundles, present in non-woody plants and non-woody parts of woody plants * in secondary xylem, laid down by a meristem called the vascular cambium in woody plants * as part of a stelar arrangement n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydathode
A hydathode is a type of pore, commonly found in angiosperms, that secretes water through pores in the epidermis or leaf margin, typically at the tip of a marginal tooth or serration. Hydathodes occur in the leaves of submerged aquatic plants such as '' Ranunculus fluitans'' as well as herbaceous plants of drier habitats such as ''Campanula rotundifolia''. They are connected to the plant vascular system by a vascular bundle. Hydathodes are commonly seen in water lettuce, water hyacinth, rose, balsam, and many other species. Hydathodes are made of a group of living cells with numerous intercellular spaces filled with water, but few or no chloroplasts, and represent modified bundle-ends. These cells (called ''epithem cells'') open out into one or more sub-epidermal chambers. These, in turn, communicate with the exterior through an open water stoma or open pore. The water stoma structurally resembles an ordinary stoma, but is usually larger and has lost the power of movement. Hy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leaf
A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, flower, and fruit collectively form the shoot system. In most leaves, the primary photosynthetic tissue is the palisade mesophyll and is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of ''Eucalyptus'', palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves are flattened and have distinct upper (adaxial) and lower ( abaxial) surfaces that differ in color, hairiness, the number of stomata (pores that intake and output gases), the amount and structure of epicuticular wax and other features. Leaves are mostly green in color due to the presence of a compound called chlorophyll that is essential for photosynthesis as it absorbs light ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Root Pressure
Root pressure is the transverse osmotic pressure within the cells of a root system that causes sap to rise through a plant stem to the leaves. Root pressure occurs in the xylem of some vascular plants when the soil moisture level is high either at night or when transpiration is low during the day. When transpiration is high, xylem sap is usually under tension, rather than under pressure, due to transpirational pull. At night in some plants, root pressure causes guttation or exudation of drops of xylem sap from the tips or edges of leaves. Root pressure is studied by removing the shoot of a plant near the soil level. Xylem sap will exude from the cut stem for hours or days due to root pressure. If a pressure gauge is attached to the cut stem, the root pressure can be measured. Root pressure is caused by active distribution of mineral nutrient ions into the root xylem. Without transpiration to carry the ions up the stem, they accumulate in the root xylem and lower the water poten ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.png "Click for more on -> Leaf")