Science Fair Project on Plant Growth

Do you want to create an amazing science fair project on Plant Growth? You are in the right place. Read the below given article to get a complete idea on plant growth: 1. Meaning of Plant Growth 2. Conditions for Plant Growth 3. Growth Curve of Plants 4. Conditions Necessary 5. Phases 6. Measurement 7. Steps 8. Growth Rate.

Contents:

1. Science Fair Project on the Meaning of Plant Growth
2. Science Fair Project on Conditions for Plant Growth
3. Science Fair Project on the Growth Curve of Plants
4. Science Fair Project on Conditions Necessary for Plant Growth
5. Science Fair Project on the Phases of Plant Growth
6. Science Fair Project on the Measurement of Plant Growth
7. Science Fair Project on the Steps Involved in Plant Growth
8. Science Fair Project on Growth Rate in Plants

Science Fair Project # 1. Meaning of Plant Growth:

Plant growth is a complex phenomenon associated with numerous physiological processes, both of constructive and destructive types.

Constructive process leads to the formation of various nutritive substances and the protoplasm, while destructive process is responsible for their breakdown.

The protoplasm assimilates the protein food and increases in bulk, while the carbohydrates are utilised in respiration and in the formation of cell-wall substance, cellulose.

Plant growth occurs by cell division and cell enlargement followed by cell differentiation. The cell division generally occurs in apical regions of shoot and root, and therefore, meristematic cells present at root and shoot apices are responsible for growth in plants.

The cambia are present in vascular bundles of root and shoot of dicot plants. They help in increasing thickness of stem and root due to secondary growth.

In some plants, the cambium is also found just beneath the epidermis and above cortex, which is referred as cork cambium.

Thus, overall definition of plant growth is: a permanent and irreversible increase in size and form attended by an increase in weight.

Water, oxygen and nutrients are very essential for growth. The plant cells grow in size by cell enlargement which in turn requires water. Thus, plant growth and further development is intimately linked to water status/availability water also provides medium for enzymatic activity.

Oxygen helps in releasing metabolic energy, so essential for growth activities.

Nutrients (macro and micro essential elements) are required by plants for synthesis of protoplasm and act as source of energy.

Temperature:

In addition, every plant organism has an optimum temperature range best suited for its growth. Any deviation from this range could be detrimental to its survival.

Environmental signals such as light and gravity also affect certain phases/stages of growth.

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Science Fair Project # 3. Growth Curve of Plants:

Whether the growth rate is studied of a cell, a plant organ, a whole plant or the whole life-cycle of plant and whether the growth rate is measured in terms of length, size, area, volume or weight.

It has been found that though in initial stages, a little decrease in weight may occur due to utilization of reserved food, the growth rate increases slowly during the phase of cell elongation or enlargement and again slows down during the phase of cell maturation till it stops.

The period during which the growth rate in any term is plotted against time always a S-shaped curve is obtained. This is known as the sigmoid curve. An analysis of the curve shows a slow start, gradually attaining a rapid growth rate followed by a period of slow growth and ultimately a decline.

The rate of plant growth is slow in the initial stages, known as lag phase, and increases rapidly later on, known as log phase (exponential phase). The growth again slows down due to the limitation of nutrients, and called steady phase.

The rate of growth can be measured by an increase in size or area of an organ of the plant, such as leaf, flower or fruit in a unit time. The rate of growth is called efficiency index.

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Science Fair Project # 4. Conditions Necessary for Plant Growth:

As growth is brought about by the protoplasm, the conditions for growth are the same as those that maintain the activity of the protoplasm.

They are as follows:

a. Supply of Nutritive Materials:

Growth can only take place when the protoplasm of the growing region is supplied with nutritive materials. The protoplasm assimilates these materials and builds up the body of the plant. Carbohydrates make a source of energy.

b. Supply of Water:

An adequate supply of water is absolutely necessary to maintain the turgidity of the growing cells. Turgidity is the first step towards growth. The protoplasm can only function when it is saturated with water. However, abundant supply of water is lost due to transpiration, and only small amount is required for actual growth.

c. Supply of Oxygen:

Supply of free oxygen is indispensable for the respiration of all living cells. This is an oxidation process by which the potential energy stored in the food is released in the form of kinetic energy, and used by the protoplasm for hundreds of activities.

d. Suitable Temperatures:

The protoplasm requires a suitable temperature for its activities. At a low temperature, it ceases to perform its functions or does so very slowly, whereas a temperature of 45° to 50°C coagulates and kills the protoplasm.

However, the protoplasm maintains its activities within a certain range of temperature. This is called the thermotonic effect of temperature. The optimum temperature is generally from 28° to 30°C, while the minimum temperature is about 4°C.

e. Light:

However, this condition for growth is not absolutely necessary in initial stages. In fact plants grow more rapidly in the dark than in the light. However, stomata remain open and chloroplasts function normally preparing food substances (carbohydrates) only in the presence of light. All this happens due to phototonic or stimulating effect of light. Continued absence of light is quite harmful to plants.

Plants grown in the dark or in very weak light have delicate, soft and slender stems and branches with elongated internodes, are pale-green or pale-yellow in colour and sickly in appearance. On such plants generally the flowers and fruits are not produced.

The leaves of such plants are small, pale-yellow in colour and often remain under-developed, and the roots are poorly developed. Plants showing such characteristics are called etiolated, and the phenomenon, etiolation.

The relative length of day and night has a profound influence on the production of flowers and fruits.

f. Gravity:

This factor determines the direction of growth of particular organs of the plant body. The roots grow towards force of gravity, and the stem against it. This process is called geotropism. The roots are positively geotropic, while the stems are negatively geotropic.

Besides all-above-mentioned factors, salt, mineral deficiencies and stress factors also influence the rate of growth.

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Science Fair Project # 5. Phases of Plant Growth:

Generally in plants growth is restricted to meristematic regions only. These meristems may be apical lateral or intercalary. The growth in length is due to gradual enlargement and elongation of the cells of the apical meristems, i.e., root-apex and shoot-apex.

However, in dicotyledonous angiosperms and gymnosperms the growth in thickness is due to the activity of the lateral meristems, i.e., interfascicular cambium, intrafascicular cambium and cork cambium. Growth is not a very simple process.

Before completion of this process a meristematic cell has to pass to three important phases:

a. The formative or meristematic phase;

b. The phase of elongation

c. The phase of maturation, and 

d. Grand period of growth.

a. The Formative or Meristematic Phase:

This is restricted to the apical meristem of root and stem. The cells of this region constantly divide and multiply in number. They have abundant protoplasm, a large nucleus and a thin cellulose wall.

The meristematic phase has constantly dividing cells both at the root apex and the shoot apex. The cells in this region are rich in protoplasm, possess large conspicuous nuclei and their cell walls are primary, thin and cellulosic with abundant plasmodesmata.

The Phase of Elongation:

This lies immediately behind the formative phase. The cells do not divide in this phase, but they increase in size. The cells enlarge in size and elongate until they reach their maximum dimension. In the root, this phase occupies a length of a few millimeters, and in the stem a few centimeters.

The cells just next to meristematic zone represent the phase of elongation. Increased vacuolation cell enlargement and new cell wall deposition are the characteristics of cells in this phase.

The Phase of Maturation:

This is further behind, and here, the cells start maturing to obtain a permanent size. The thickening of the cell-wall takes place in this phase.

Further, away from the apex, i.e., more proximal to the phase of elongation lies the portion of the axis which is undergoing the phase of maturation. The cells occupying this zone, attain their final size, wall thickening and protoplasmic modifications.

Most of the tissue/cell types represent this phase. Hence, at this phase, all the diverse tissue types observed in epidermis, cortex, vascular tissue, etc., both in root and apical end of a stem.

Grand Period of Growth:

The time interval from the formative phase to maturation phase is called the grand period of growth. Every cell of the organ of plant body, shows a variation in the rate of its growth.

The growth is at first slow, then it accelerates till a maximum is attained, then it falls off quickly, and gradually slows down till it comes to a standstill. This growth of organ or cell of a plant as a whole extending over the whole period is actual grand period of growth.

Within the grand period, variations in growth occur due to external and other causes. There is thus the diurnal variation of growth. Light inhibits growth, and too intense light even checks growth altogether. Thus plants grow quicker in night than in comparison of day.

There is also seasonal variation of growth. During winter, the growth of many plants is checked or becomes very slow, while during spring, growth proceeds rapidly.

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Science Fair Project # 6. Measurement of Plant Growth:

Growth is a complex natural phenomenon, and generally takes place at the apical regions of the plant. Thus, the growth in length can easily be measured with the help of auxanometer.

This phenomenon, you can understand by following simple experiments:

An auxanometer is used to measure the rate of growth in terms of shoot length.

Practicals:

Experiment:

Object:

Measurement of growth in plants.

Requirements:

Auxanometers:

(i) Arc auxanometer, and 

(ii) Pfeffer’s automatic auxanometer.

(i) Arc Auxanometer:

It consists of a vertical stand with a pulley to which is attached a long thread and a needle or pointer movable over a graduated arc. One end of the thread is tied with the growing point of the plant and another is stretched with a suitable weight.

(ii) Pfeffer’s Automatic Auxanometer:

It consists of a vertical stand with two pulleys. One of these two pulleys possesses a thread carrying two weights at either ends to keep it stretched. This thread on one side is also attached with a fine scratching pointer which touches a smoked drum. Another pulley is also provided with a thread of which one end is tried with the growing point of plant and another is stretched with a suitable weight.

Observation and Explanation:

(i) With the growth of plant, the weight moves the thread down and the movement of needle can be read easily on the scale.

There exists a notable ratio between the size of pulley and the needle. If pulley is 4 inches with the needle 20 inches from the centre of the disc of pulley, growth will be magnified ten times on the scale.

It can easily be illustrated by an example:

If indicator moves 4 cm in 8 hours and the magnification is 10 times, then the actual growth is:

(ii) With the growth of plant first pulley makes moving the another which in turn moves the pointer. This pointer moves downwards and traces a spiral on the rotating smoked drum. Thus the growth for a certain period is recorded.

Growth can also be measured by an increase in weight both fresh and dry, and volume of the plant. The increase in the number of cells, especially in algae, cyanobacteria, yeast, etc. The measurement of area or volume of an organ of the plant also gives information about the rate of growth.

Science Fair Project # 7. Steps Involved in Plant Growth:

1. Vivipary:

This is a special type of germination of seed. This is the phenomenon of germination of seeds within the fruit, while the fruit is still attached to the mother plant. This type of seed germination occurs in several species of the plants to mangrove vegetation, such as Rhizophora, Sonneratia, Ceriops, Kandelia, etc.

The seeds in such plants do not germinate in the soil due to high salt contents and deficiency of oxygen in the marshy habitats. In such plants, the seed dormancy is absent. Instead, embryo grows continuously without any hinderance inside the fruit while it is attached to the mother plant. (Fig. 6.3).

During this type of germination, the hypocotyl elongates and pushes the radicle out of the seed and fruit. Thereafter, the hypocotyl grows more vigorously and becomes club-like, and sometimes attains a length of 50 cm or so, as in Rhizophora. The young green seedling comes out of the fruit showing the long hypocotyl and radicle.

The cotyledons act as haustoria and suck food from the parent plant. When the seedling gains weight, it gets detached from the fruit, and falls down vertically like a dart. Now the radicle penetrates into the mud. The lateral roots immediately develop on this seedling, and it soon establishes as a plant in the muddy soil. The plumule remains above the water level and grows safely.

2. Conditions Necessary for Germination:

Water, temperature, oxygen and light are the factors which are responsible for seed germination. Water is needed to bring about the vital activity of the dormant embryo to dissolve various salts and organic substances stored in the cotyledons or in the endosperm; to facilitate necessary chemical changes; and to help the embryo to come, out easily by softening the seed-coat.

Temperature requirement of seeds varies depending on the species. Seeds of many species germinate only if the temperature is within a certain range. Very low and very high temperatures retard or prevent germination.

Wheat grains may germinate at a temperature a little above 0° C while the lowest limit for maize is 5-10°C. Oxygen is essential for the germination of germinating seeds. Seeds buried in the deeper layers of the soil remain dormant for want of oxygen.

They readily germinate when the soil is ploughed. Seeds of aquatic plants can obtain their oxygen requirements from the air dissolved in water. Light is an essential factor for the germination of seeds of mistletoe and many epiphytes.

They will not germinate in the dark. In some plants seed germination is favoured by light. This is the case with seeds of lettuce (Lactuca sativa) and many grasses. Many seeds are however, indifferent to light. In others, light has a retarding effect and may even completely prevent germination (e.g., Nigella, Phlox, onion, and lilies).

3. Juvenility:

After germination, a young plant develops vegetatively for some time and lacks the capacity to form flowers. This early phase of the vegetative growth of the plant is known as juvenile phase. The juvenile phase can be recognized from the adult phase by certain striking features such as leaf shape, habit of the stem and the size of the thorns if present. Such differences also occur in some lower plants.

The change from the juvenile to the adult phase is gradual, as shown in the leaves of cotton. Delphinium and Ipomoea, or it may be abrupt. The latter condition represents heteroblastic development. For example, in some plants the first few leaves are normal, whereas the subsequent leaves may be phyllodes, (e.g., Acacia spp).

It has been advocated that the juvenile and adult parts of the plants are also physiologically different. In the juvenile phase, the plant does not respond to stimuli that can induce flower formation. In woody plants, branches cut from the juvenile stage root more readily than those derived from the adult stage. This is a point of significance in vegetative propagation.

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Science Fair Project # 8. Growth Rate in Plants:

The expression of increased growth per unit time is termed growth rate. Thus, rate of growth can be expressed mathematically. An organism, or a part of the organism can produce more cells in a variety of ways.

The growth rate can be arithmetic or geometrical increase:

In arithmetic growth, following mitotic cell division only one daughter cell continues to divide while the other differentiates and matures. The simplest expression is arithmetic growth, e.g., a root elongating at a constant rate.

Mathematically, it is expressed as:

Geometrical Growth:

However, in most systems, the initial growth is slow (lag phase), and it increases rapidly thereafter at an on exponential rate (log or exponential phase). Here, both the progeny cells following a mitotic cell division retain the ability to divide and continue to do so.

However, with limited nutrient supply, the growth slows down leading to a stationary phase. If we plot the parameter of growth against time, we get a typical sigmoid or S-curve. S-curve is characteristic of every living organism growing in a natural environment. It is typical for all cells, tissues and organs of a plant.

However, S-curve of the individual cells/tissues/organs/organisms may not be synchronous, i.e., not at the same phase of the curve. For example, one cell may enter stationary phase while other is just entering the lag phase. Individual leaves are initiated, and abscised (each with a S-curve), but the plant/branch on which they occur could be still in exponential (log phase) or other places of growth.

The exponential growth can be expressed as:

W₁ = W_oer₁

W₁ = final stage (weight, height, number, etc.)

W_o = initial size at the beginning of the period

r = growth rate

t = time of growth

e = base of natural logarithms

Here, r = is the relative growth rate and is also the measure of the ability of the plant to produce new plant material, referred to as efficiency index. Hence, final size of W₁ depends on initial size, W₀.

Quantitative comparisons between the growth of living system can be also made in two ways:

(i) Measurement and the comparison of total growth per unit is called absolute growth rate.

(ii) The growth of the given system per unit time expressed on a common basis, e.g., per unit initial parameter is called relative growth rate.

For example, two leaves A and B of different area sizes show exact absolute increase in area in the given time to give leaves A’ and B’. However, one of them has much higher relative growth rate.

Apical Dominance:

In many herbaceous plants which produce aerial stems, growth in length takes place at the apex of the main axis of the plant. Although a lateral bud is present in the axil of every leaf, side branches do not often develop from these buds as long as the terminal bud retains its vigour and continues to grow.

If the terminal bud is destroyed or is artificially removed, development of the lateral buds usually starts at once. This inhibiting effect of a terminal bud upon lateral bud development is called apical dominance and is much more pronounced in some species than in others.

The phenomenon of apical dominance is usually also in evidence in all woody plants on which true terminal buds form. The lateral buds on current shoots usually do not develop unless the terminal bud is destroyed or injured.

Development of the lateral buds on older shoot segments is of more frequent occurrence, indicating that the inhibitory effect of the apical bud diminishes with greater distance of the lateral buds from the apex of the stem.

The controlling effect of the apical bud in apical dominance results from its auxin content. Several other growth regulating compounds have similar effects upon the growth of lateral buds, if applied to the cut surface of a detipped stem.

For example, when potato tubers begin to sprout the apical buds grow rapidly but the lateral buds usually fail to elongate. If, however, the apical and lateral buds are cut out of the parent tuber both grow at similar rates.

Treatment of the tubers with ethylene chlorohydrin which causes the destruction of auxin, results in the rapid growth of both lateral and apical buds. This supports that the growth of lateral buds is checked by auxins formed in the apical buds.