Growth is the process of an individual organism growing organically, a purely biological unfolding of events involved in organism. Growth is also defined as an irreversible change in the size of a cell, organ or whole organism. Growth is also defined as an irreversible change in the size of a cell, organ or whole organism. Growth is also the increases in the amount of the goods and services produced by an economy over time.

            Growth is the progressive development of an organism usually expressed as dry weight (total of the part wire interested in such as grain), height, length, diameter.
            Growth of an annual plat related time is an shaped curve for an or one growing season for a perennial plat    

Growth related to the factors affecting it.
                          h = + (+1, x2, v3, ……Xn)
                          a = measure of growth
                          Xi = growth factors
It may also be the increase in cell number without changes in volume or weight. Commonly, growth is the increase in the amount of living material (protoplasm) which leads to an increases in the cell size and ultimately cell division.
The increase in protoplasm is brought about as water, carbon dioxide and inorganic salts are transformed into living material. Growth occurs only in living cells by metabolic processes involved in the synthesis of proteins, nucleic acids, lipids and carbohydrates at the expenses of metabolic energy provided by photosynthesis and respiration.
            The growth and developmental patterns of plants are commonly used to classify plants into groups. Annual plants complete their entire life cycle, from seed to seed, in a single growing season, whereas biennial plants require two growing seasons. Perennials grow years after often taking years to mature. In herbaceous perennials the roots and shoots can remain alive undefinetely but the shoot system may be killed by frost. Each spring shoot growth resumes from adventitious buds at the crown of the plant. In woody perennials, both the shoots and the roots remain alive undefinite.
            Indeterminate plants are those whose main axes remain vegetative and in which flowers form in axillary buds. These plants as cucumbers, peas and grapes. A determinate plant’s main and secondary axes terminate in a flower bud and consequently shoot elongation stop as in sweet corn, bush tomatoes.
            Plant growth is often measured as a change in area, length (h), volume, height, wet or dry weight. These methods may not always be a satisfactory measure of growth at a particular stage of plant development, i.e, a germinating seed may show an overall loss in dry weight due to the utilization of food reserves during respiration, although the seed is definitely growth as evidenced by its emerging roots and shoots.
            The relative growth rate (RGR) which is the size measure per unit interval of time has two components. The net assimilation rate (NAR) and the leaf area (LAR). The NAR is the rate of increase of dry weight per unit of leaf surface which is a measure of the amount of photosynthetic product going into plant material. The LAR is the ratio of leaf area to dry weight which is the measure of the proportion of the plant that is engaged in photosynthesis. Combined they give a relative description of growth over time based characteristics.
Plant is a unit in a living ecosystem. Plants are also what is called a living creature. Of course as living beings, plants have characteristics similar to other living creatures. As with the growth and development. The process is also influenced by several factors relatively directly or indirectly. Here are some up the processes that affect plant growth and development.
The internal Factors
            In influencing the development and growth in plants, internal factors related to genetic, growth regulators, CN ratio and physiological factors include the plant. Both of these factors can be described in more deeply because it contains a variety of circumstances.
Genetic Factors
            Growth and development process starts from the germination process. This process begins with water uptake (inhibition). Water is then absorbed into the body resulting in dissolution of pieces of the institution. Besides dissolving food, absorb water also serves as substances induced layer of hydrolytic enzymes. After that the enzyme will be controlled by the genes of plants.
            Germination process also requires that the metabolic process of plants can live. This metabolic processes requiring metabolic enzymes support that aims to regulate the metabolic rate of growth and development of plants that can be set to be optimal and its all arranged by the genes of plants. In genetic factors we have;
i.          Field Crops: Yield potential is determined by genes of the plant. A large part of the increase yield over the year has been due to hybrids and improved varieties. Other characteristics such as quality, disease resistance, drought hardiness are determined by the genetic resulting from genetic. Genetic engineering is now becoming an important tool in changing a plants potential.
ii.         Nursery Crops and Turf: not interested in total as much as appearance. Example is Barmudagrass.
a)     Coastal Barmudagas:  as a forage the grower is interested in yield and feed quality.
b)     Tifdwarf- Golf greens interested in appearance, cover wear resistance not how much total growth occurs.
ii.         Variety and Plant Nutrient Needs: hybrid corn producing 200 bu/ac requires more plant nutrients than a hybrid producing 100 bu/ac. As potential crop yields are increased, the plant nutrients required are increased. Current research in the solid science and genetics department is concerned with developing corn hybrids that use nitrogen more efficiency. Produce more gain per pound of N-fertilizer.
iv.        A producer has control over the genetic factor by his choice of variety.
Field Crops è highest yielding, disease resistant, etc.
Nursery è Best appearance – dwarf vs. larger shrubs.
Physiological Factor
            Physiological factors are factors derived from the functional process at the cellular level in plants. All activities conducted by plant cells also affect the process of development and growth in plants. Growth and development will involve a variety of hormones and vitamins. Hormones and functions at each level of growth and development.
            Hormones that affect growth and development are as follows hormone auxin, gibberealin, ethylene, cytokminus, absistal acid, kalin, tranmalin acid antokalin, falokalin, rhyzokalin and kaukokalin, addition of hormones, vitamins also affect growth and development.
Examples are vitamin, riboflavin, ascorbic acid, thiamine, plyridoxine and ricotimic acid. Vitamins serve as components that are capable of activating the enzymes.
C/N Ratio
            The Ratio of carbohydrates and nitrogenous compounds covers the pattern of growth. Presence if more carbohydrates favours good vegetative growth, flowering and fruiting presence of more nitrogenous compounds results in poor vegetation growth flowering and fruiting.
Growth regulators
            Plant hormones are produced naturally by plants and are essential for regulating their own growth. They act by controlling or modifying plant growth processes, such as formation of leaves and flowers, elongation of stems, development and ripening of fruit.
            In modern agriculture, people have established the benefits if extending the Use of plant hormones to regulate growth of other plants. When natural or synthetic substances used in this manner, they are called plant growth regulators. The application of plant growth regulators in agriculture has started in the 1930s in the USA. Ethylent a naturally occurring substance, is one of the first plant growth regulators being discovered and used successfully for enhancing flower production in pineapple. Its toxic effects to human beings are low. Synthetic substances that mine such naturally occurring plant hormones were also produced, since then the use of plant growth regulators has been growing significantly and becoming a major component in modern agriculture.
            The three common plant growth regulators are; over the years, ethylene has continued to be among the best known examples of plant growth regulators. It is a gasous plant hormone playing a key regulatory role in ripening of many types of fruits, including banana, apples, pear and melons. It can be produced naturally by ripening fruit or from synthetic sources such as ethephon. Try this experiment: put raw bananas and a ripening fruit (e.g apple) in the same paper bag and cover it up.
Ethylene produced by the ripening apple will speed up the ripening process of bananas, giving you the ripe bananas next morning.
            Another major class of plant growth regulators are auxins and related compounds. The earliest study on auxins was intended for the initiation and acceleration of the rooting of cuttings. The natural auxin, indole-3-acetic acid was identified in 1930s. later on, synthetic auxins such as indolebutyric acid and map thylacetic acid were developed. Synthetic auxins have a wide range of applications including the prevention of fruit drop in apples.
            The recently reported “suspect” causing “exploding were melon” is also a plant growth regulator, a chemical called for forchlorfeuron. It is a synthetic plant growth regulator under the group called phenylurea type cytokinin, which can induce cell division and cell differentiation.
            Forchlorfenuron is known to increase size and yield of fruits such as grapes, kiwifruits and watermelon. Proper use of forchlorfenuron that is following the good agricultural practice (GAP) will result in minimal residue in food and hence low food safety risk. Ripening experiment put a raw banana into a paper bag together with a ripening apple, cover it up, place over night. Next morning you will find the banana ripened as compared with one that is left in air. The effect is due to the banana’s exposure to ethylene released by the ripening apple or other ripening fruits that may be present.
            As a well accepted primciple, all pesticides, including plant growth regulators, have to be registered with the competent authority before application in agriculture. The safety and efficacy will be thoroughly assessed during the registration process. Proper use of these registered pesticides including plant growth regulators in accordance with (GAP) will result in minimal residue in food of insignificant food safety risk (GAP) is a set of nationally authorized conditions to use the pesticides safety (e.g. in relation to public health and environmental safety concerns) for affective and reliable pest control. Various conductions, such as the type of commodities authorized for using the pesticides, the recommends application rates, frequencies and amount as well as the duration between the last application of the pesticides and harvest, are prescribed in the (GAP).
            In conclusion, plant growth regulators are a group of chemicals for controlling and enhancing the natural plant growth processes to better meet the requirements of food supply in general. Mechanisms are in place under the codex system to oversea residue of pesticides, (including plant growth regulators) in food for setting standard and public health projection.
phenoxyacetic acid to increase blossom and fruit set in tomatoes is also successful. Auxins are also commonly used in tissue culture procedures to initiate rooting in explants or callus (4).
Gibbereltins are a group of naturally occurring plant hormones that affect cell enlargement and division which leads to internode elongation in stems. They have a dwarf reversing response allowing certain dwarf cultivars to grow to normal height when treated with gibberellin. They affect many developmental processes, particularly those controlled by temperature and light such as seed and plant dormancy, germination, seed stalk and fruit development (7).
Gibberellins are used commercially to increase fruit size of “Thompson Seedless’ grapes. They ar applied at fruit set or shortly thereafter. They also promote male flower initiation in cucumbers when pollen is wanted for hybrid seed production and may overcome the cold requirement for flowering of some perennial plants (4).
Cvtokinins Drimarilv Dromote cell division but they also influence cell enlargement, tissue differentiation, dormancy, phases of flowering arid fruiting and retardation of leaf senescence (4).
Cytokinins and auxins interact to affect differentiation. A high auxin to low cytokinin ratio stimulates root development, whereas a low auxin and high cytokinin ratio stimulates bud development. Equal concentrations of auxin and cytokinin results in undifferentiated tissue or callus (7).
Cytokinins are not commonly used in agriculture, however, cytokinin may be used in tissue culture to induce shoot development (4).
Ethylene is a gas that diffuses readily. throughout the plant. It is produced in meristematic tissues, ripening fruits, senescing flowers and fruits arid germinating seeds. The cuticular coating of the plant tends to prevent losses from the plant (4)
Synthetic ethylene-releasing compounds such as ethephon have several valuable commercial applications Ethephon is used to ripen bananas, pineapples, melons and tomatoes, and when applied as a preharvest spray it promoters unilorm opening of apples, cherries and pineapple. It is used to increase the production of female flowers on cocumbers which develop fruits and increase yields. High concentrations of ethylene Tiay be harmfe. l to plants, inducing leaf abscission and hastening senescence of flowers and fruits (4).
Abscisic acid interacts with other hormones in the plant, counteracting their growth-promoting effects. It inhibits rather than stimulates plant growth. Abscisic acid promotes dormancy in seeds and is involved in leaf and fruit abscision. The abscisic acid content of leaves increases following water stress, where it induces closure of the storr era (4) Abscisic acid is expensive to synthesize and no commercial applications are as yet in use.
Greenhouse growers and nurserymen commonly use growth retardants in managing plant growth. Many synthetic compounds are available to dwarf plants, increase branching and manage flowering to produce compact flowering plants in a timely manner. Use of growth retardants is specific by species and desired result. . .

Plant growth and development are influenced by physical, chemical and biological components in the plants environment. Any factor in the plants’ environment that is less than optimum, whether it is deficient or in excess, will limit plant growth (17).
            Light has three principle characteristics that affects growth quantity, quality and duration.
            Light quantity refers to the intensity or concentration of sunlight and varies with the season of the year. The maximum is present in the summer
Plants respond to light of the wavelengths from 300-800 nm. Plants grown in the absence of light are Said to be etiolated. Etiolated plants lack chlorophyll, are tall and spindly with long internodes and havesmall leaves that have failed to expand. Their morphological expression of etiolation is related to the effect of light on auxin distribution and synthesis . There are no anatomical differences in the tissues formed in the light or dark, however, light accelerates many phases of growth while inhibiting certain aspects of internode elongation Light can have an effect on the morphology of the plant. Leaves on the same plant may differ depending on whether they are sun leaves or shade leaves. Sun leaves are often thicker with extra layers of palisade parenchyma, and shorter petioles. They are also smaller in area .
A plants response to light will vary depending on the intensity, duration and wavelength of the light it receives.
Light intensity refers to the concentration of light waves striking the leaf surface (7). Light intensity has been expressed in foot candles by scientists and growers until recently. Watts per square meter or microeinstein’s per square centimeter are more useful and describe energy per unit area which can be related directly to power consumption for cost analysis.
Light intensity is high where there are no clouds and little moisture in the air. Water vapor in the atmosphere absorbs radiation so light intensity is lower in cloudy or humid areas. Light intensity will vary with the elevation, latitude, season and the weather conditions affecting the amount of water vapor in the air .
Photo processes in the plant ‘ary in the intensity of the light required to initiate the reactions and the effect of the intensity on the rate of the reaction (7). The rate of photosynthesis drops on cloudy days. However, not all plants require high light intensities. Shade plants may require as little as 1/10 full sunlight for optimum growth and higher levels may cause sun burning, scald and in severe cases death if sufficient soil moisture is not available.
Photoperiodism refers to the physiological responses of plants to variations in the duration of daylight (4). The shift from vegetative growth to reproductive growth is a response to the photoperiod. The length of the vegetative growth period can be extended by growing plants in photoperiods that do not induce flowering. Daylength may also affect the time to first flower,, the number of flowers produced and the number of fruit set (12). Likewise short daqs and cooler temperatures initiate dormancy in many temperate zone perennial plants.
The light reactions of the plant are carried on by different pigment systems that absorb specific wavelengths of light, i.e., blue, green, yellow or red light (12). Chlorophyll absorbs that radiant energy necessary for the photo-processes of photosynthesis (7) Chlorophyll absorbs light in the red and blue portions of the spectrum (7). Phototropism, the movement or bending of stems, leaves and flowers toward light, is triggered by blue light (4). This process is believed to occur due to the accumulation of auxin in the shaded side promoting cell growth. Thus the bending movement toward the light source is a result of increased cell growth on the shaded side (4). When leaves are subjected to high levels of radiation, they may orient themselves parallel to the energy source in order to minimize the harmful effects of the intense radiation .
Although incoming light in the typical greenhouse in mid-winter often does. not exceed 1000-1 500 foot candles in many locations, good growth of lettuce may be obtained at intensities as low as 500 foot-candles. Bolting results from long days and high tempera tures so most varieties of greenhouse lettuce are not grown in late spring add early summer (18).
Early spring cucumbers, at the seedling stage, respond to supplemental light. Daylength of about 12-14 hours with 1800-2000 foot candles at the plant level should be provided. Crowding should be avoided to prevent plants from becoming spindly (18).
Tomatoes grown in the late fall or early winter should be exposed to as much light as possible during normal daylight hours. However, artificial lights should not be used to extend the daylength as tomataes are plants which flower and fruit better if daylength is twelve hours or less. If artificial lights are used, at least 500 foot candles at the leaf surface should be provided. Supplementary artificial light may only be economically feasible for tomatoes at the seedling stage where a greater number of p lants can be illuminated per square foot .
The temperature range that supports plant growth is generally from 40-97 degrees F (4.5-36 degreesC). Optimum temperatures for growth vary with the species and the stage of development and usually fluctuates night to day. Several growth processes are sensitive to temperature. Among these are respiration, part of the photosynthetic process, maturation, flowering, fruit ripening and dormancy. Photosynthetic rates are determined mainly by light intensity, 002 levels and temperature (11). Temperature has little effect on photosynthetic rate from 50-86 degrees F (15-30 degrees .C) until light and 002. become saturated for the photosynthetic process. At this point, an increase in temperature from 68-86 degrees F (20-30 degrees C) results in a marked increase in the photosynthetic rate (11). On warm days, midday leaf temperatures may be high and inhibit photosythetic activity (12). Not only are metabolic processes reduced at high leaf temperatures, but moisture stress, from increased transpirational losses, results in stomatal closure which decreases the supply of 002 to the chloroplasts slowing photosynthesis.
Respiration rates increase rapidly as the temperature increases. Temperature is a controlling factor in establishing the compensation point of greenhouse crops, the point at which the rate of 002 consumed in photosynthesis equals the rate of C02 given off in respiration, because of its affect on respiration rate. As temperatures rise the level at which the compensation point occurs for a particular light level or 002 concentration will decrease. A cessation of growth occurs when the rate of respiration increases more rapidly than the rate of photosynthesis, resulting in a depletion of food reserves.
Maintaining day/night temperatures at specific levels can increase yield and quality of crops. Optimum growth of many crops occurs when greenhouse temperatures are cooler at night than during the day. The response of plants to diurnal temperature fluctuations is referred to as thermoperiodicity. Temperature effects on flowering may be direct or inductive. The effect of temperature is dirt when flower initiation occurs during the period of temperature treatment. If a specific temperature induces a change within the plant which permits flowering at another time, the effect is considered to be in-directive. Verbalization is the inductive effect of cold temperatures on flower initiation. Many biennials and perennials require cold treatments to induce flowering.
Root temperatures also affect the rate of plant growth. Increasing root temperatures up to about 26 degrees C (76 degrees F) nay increase top growth and the uptake of inorganic ion. This is true of many hydroponically grown crops, cucumbers in particular.
Green plants require oxygen for normal growth and development. The energy released in cellular respiration, from the breakdown of carbohydrates and complex organic molecules, consumes oxygen and releases C02. Most plants retire continuously, day and night, requiring a continuous supply of oxygen. Anaerobic respiration or fermentation occurs in the absence of oxygen. The products of this form of respiration are often deleterious to the plant and the energy released is relatively small compared to aerobic respiration. Roots also require oxygen for aerobic respiration which they obtain directly from the growing media. The absorption of salts and root extension are dependent upon the energy supplied from respiration. Poorly aerated growing medias result in a decrease in water absorption due to a reduction in the permeability of the root cells. After extended periods of poor root aeration the roots stop growing and are more susceptible to disease.
Seeds require oxygen to germinate. Seed germination is inhibited by a lack of oxygen for prolonged periods. Often thick or oily seeo oats rnjst be removed from the seed so oxygen will be available to the embryo. Compacted or water logged soils or growing media can also create an oxygen-less environment and seeds will not germinate. .
L. Carbon Dioxide
Carbon dioxide(CO2) is a raw material required for photosynthesis. The atmospheric 002 concentration at the plant level is the most important rate determining factor for further increases in photosynthesis and yield (18) C02 concentrations may fall below the ambient air concentration .03% (300 ppm) in the greenhouse when weather conditions restrict ventilation o infiltration. A crop in a tightly clOsed greenhouse will soon deplete the 002 concentration which reduces growth and production by slowing or stopping photosynthesis. Unless replaced, the 002 concentration will remain at the plants compensation point, the level at which the 002 produced from respiration equals the amount used for photosynthesis. No growth occurs at this point. 
When weather conditions permit. ventilation is an effective method of maintaining C02 concentrations at the normal air levels. However, plants respond favorably to higher C02 concentrations, making greenhouse supplementation of 002 an effective method of increasing plant growth (11). Although the 002 response is dependent upon light intensity, beneficial effects are obtained over a wide range of light intensities, either natural or artificial. 002 enrichment is of special significance in hydroponics culture as decaying organic matter in the soil, a source of 002, is not present (18).
002 is commonly supplied at 800-1600 p m via gas 002 generators or large tanks of liquid 002 defending upon the cost corriparison between the two and the availability of the bottled carbon dioxide.
Air pollutants

Air pollution is an important problem for producers of greenhouse crops. The sources of air pollution are increasing as new industries and highways are built. This is a particular problem for horticultural operations near urban and industrial areas. Among the phytotoxic pollutants are ozone, peroxyacel nitrates, oxides of sulfur, hydocarbons, rluorides, carbon monoxide, herbicides, fumigants, mercury vapors (do not use mercury tliermomete’s in greenhouses), and phytotoxic gases produced from incomplete combustion of 002 generators. It may be necessary for greenhouse owners to move to areas where phytotoxic gases are not present, or to grow species that are less sensitive to these substances.
Often leaves and flowers are first to show signs of air pollution. Unusual discolorations, spotting, twisting or turning of leaves and abortion of flowers followed by poor growth are symptoms of air pollution.
Most growing plants contain about 90% water. Water is the medium for transfer within the plant and is the solvent system of the cell. Water is one of the raw materials for photosynthesis required for the production of new compounds. ri soft tissues water pressure provides support and as plants lose water from their leaves they are cooled. A net loss of water will cause growth to stop and continued deficiency results in death.
A growing plant absorbs water from the soil and gives it off in transpiration. Enters the plant through a film of water that surrounds the leaf and as the film evaporates it is replenished by the plant. The transpiration loss of water in exchange for 002 is necessary for plant growth. Rapidly growing plants require large quantities of water, far in excess of that found in the plant for synthesis of new materials.
Moisture stress is generally detrimental to plant growth reducing both yield and quality of the crop. The degree and duration of the stress will determine how severely growth is reduced, however, growth rate may never return to the level it was before the stress (11).
The stage of growth when moist ire stress occurs is also important. Moisture stress at the time of flower initiation may significantly reduce yield. Severe stress leads to premature flower, leaf and fruit drop (11).
Transpiration leads to moisture stress if moisture is not readily available to the roots. As moisture stress increases, stomata’s close and photosynthesis is reduced. Warm dry air has a high evaporative capacity, increasing the rate of transpiration. As we II, the increase in leaf temperature resulting from high light intensity raises the rate of transpiration loss .
Poor water quality can be a major problem for growers, particularly those with hydroponic systems, due to contamination from organic and inorganic substances. Even the best domestic water supplies may contain substances that affect plant growth. Therefore, a complete water analysis is recommended for greenhouse growers. Hydroponic systems require detailed elemental analysis of irrigation waters. In order to develop an appropriate recommendation for nutrient levels in solution the concentration of existing elements in the water must be known. Adjustments can then be made in the solution for the crop to be grown. Depending on the result of the water analysis, some form of water treatment may be necessary. Water treatment may simply involve the use of a filtering system for particulate debris, or may require more sophisticated methods of ion exchange or reverse osmosis in addition to filtration. In some cases all that may be necessary is the adjustment of nutrient solution, as in hard water areas where the majority of calcium and magnesium is already provided by the water source. E71

Many people confuse plant nutrition with plant nutrition refers to the needs and uses of the basic chemical elements in the plant. Fertilization is the term used when these materials are supplied to the environment around the plant. A lot must happen before in chemical element supplied in a fertilizer can be taken up and used by the plant. Plants need is elements for normal growth carbon, hydrogen and oxygen are found in air and water-Nitrogen phosphorus, potassium, magnesium, calcium and sulfur are formed in the soil. The latter elements are used in relatively large amounts by the plant and are called macronutrients or trace elements. The micronutrients, boron, copper cobalt and chlorine of 18 elements, both macronutrients and macronutrients are essential for plant growth. Most of the nutrients that a plant needs are dissolved in water and then adsorbed by the rots ninety – eight percent of these plant nutrias      by the plant are absorbed from the soil solution and only about 2% are actually extracted from the soil particles by the root most of the nutrient elements are absorbed as charged this or pieces of moleculesions may be positively charged cations or negatively changed animals positive and negative are equally pained so that there is overall charge. For example nitrogen may be absorbed as nitrate (kNo3) has one potassium ion (kt) is a cation with one positive charge potassium nitrate (kN03) has one potassium ion and one nitrate (ca No3) has one potassium ion that has two positive charges, single charges of the calcium.
The balance of ions in the soil is very important just as ions having similar charges compete for chemical interactions and more active than others or can compete better. For example both calcium (a) and manicuring (ng) are cultural with two charges but magnesium is more active if both are in competition to be absorbed the magnesium will be absorbed. Are called marco     
TEMPERATURE: Afflicts the productivity and growth of plant depending open whether the plant variety is a warm–season or cool–season crop. If temperature and high and day length is ion coo-season crops such as broceli and spirneh will bait rather than produce the desired flower. Temperature that are two low or high for a warm-season crops such as pepper or termite can cause plan to become invaluable and not pollinate flowers.
Adverse temperatures also cause stunted growth and poor quality for example the bitterness in lecture is caused by high temperatures sometimes temperatures are used in connection with day length is manipulate the flowering of plants. Chrysanthemums will flower for a longer period of time if day high s are 59oF (15oC) the Christmas cautus forms flowers as a result of short days and how temperatures. Temperatures alone also influence flowering. Daffodils are forced to flower by putting the bubs in cold flower putting the bubs in cold storage in October at 35o 40. F ( 4oC) the cold temperatures allow the bulbs are transferred to the greenhouse in midwinter where growth begins. The flowers are then ready for acuity in 3 to 4 weeks. Thermo period refers to daily temperature change. Plants produce maximum growth when exposed to a tray temperature lost (5.5 to 8oC) higher than the night temperature. The allows the plants to photosynthesize and respire during on optimum daytime temperature and to curtail the race of color night. High   temperatures cause increased respiration sometimes being produced. For growth to occur photosynthesis must be greater than respiration.                  
Sixteen elements are considered to be essential for growth and development in higher plants. Arnon & Stout (1) considered an element essential when it 1) is required by a plant to complete its life cycle, 2) the action of the element is specific and n o other element may be substituted for it and 3) the element must exert its. Effect directly on growth or metabolism and not simply cause another element to be more readily available or antagonize a toxic effect of another element.
The essential elements are divided into two groups: the macronutrients, those required in relatively large quantities including carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium and sulfur and the micronutrients, those required in small quantities, including iron, chlorine, manganese, boron, zinc, copper and molybdenum (See Table for Internal Concentrations of Essentials Elements in plants).
Carbon, oxygen and hydrogen are obtained from the environment, specifically carbon dioxide or water. Along with chlorine, which is found in most water sources, these elements are generally not considered in the formulation of nutrient solutions.  





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