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
(N/B)
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).
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. . .
EXTERNAL FACTORS AFFECTING PLANT GROWTH
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
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 .
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.
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.
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
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
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.
Water
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.
Water
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 .
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
Nutrition
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 (2.to 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.
DEPARTMENT OF CROP SCIENCE AND LANDSCAPE MANAGEMENT
FACULTY OF AGRICULTURE AND NATURAL RESOURCES
MANAGEMENT
TOPIC: THE
INTERNAL AND EXTERNAL FACTORS THAT AFFECT PLANT GROWTH
COURSE TITLE: CROP
HUSBANDRY FIELD CROP
COURSE CODE: CLM 5II