Botany is the study of plants. The word botany is derived from the Greek word botane meaning herb or plant. Plants, being living organisms, exhibit the seven life processes. The seven life processes are described below with special reference to plants.
Nutrition
Nutrition is the process by which living organisms take in substances from the surroundings for their use. Green plants and some bacteria can prepare food from carbon dioxide and water, utilizing light-energy. This process is called photosynthesis and the organisms that carry out such a process are called autotrophs. Animals, fungi and most bacteria cannot prepare their own food. Animals ingest complex food materials and need their serve by breaking and digesting such materials. Bacteria and fungi absorb simple food materials from the surroundings. Organisms that ingest or absorb food materials are called heterotrophs.
Respiration
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Besides food, that is needed to build the body, living things also need energy for various purposes. All organisms carry out a process called respiration that involves breaking down of food materials through a number of biochemical reactions. The energy released is stored in the energy rich molecules called ATP (adenosine triphosphate).
Excretion
Two types of chemical reactions are seen in living organisms constructive and destructive. Constructive reactions are called anabolic, that involve utilisation of energy and are termed endergonic. The destructive reactions are called catabolic, that are responsible for release of energy and thus, are termed exergonic. The processes relating to anabolic and catabolic reactions are called anabolism and catabolism respectively. Anabolic and catabolic reactions together constitute metabolism. Excretion is the process of removal of waste products release during anabolic and catabolic reactions. Animals have special excretory systems, whereas plants excrete by removal of bark. Fall of old leaves is also considered as a mechanism of excretion in plants.
Sensitivity
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Living organisms are capable of responding to stimuli, internal or external. The response of an animal is quick and conspicuous because of the capability of an animal to move. Movement of the leaflets of Mimosa pudica in response to touch and that of any green plant in response to light are examples of sensitivity or irritability in plants.
When a plant or animal, is continuously exposed to a particular stimulus, it may develop new characters as adaptations. Adaptations are either short term or long term. Short term adaptations are not permanent and are reversible. Response of sensitive plant Mimosa Pudica to the stimulus of touch is a shot term adaptation. When an organism is exposed to continuous stimulus for over thousands of years, it may developed permanent adaptive features. Absence of leaves in some succulent plants and scent in flower to attract insects are examples of long term adaptations in plants. Absence of blood sucking mouth parts in male Anopheles mosquito and use of tail as a fifth limb in kangaroo, are some of the long term adaptations in animals.
Movement
Movement is a character life process exhibited by most animals. Movement of the whole body is also seen in some bacteria and some colonial plants. Most plants show the movement of only body parts like petals or leaves. Movement may be seen within the cell. Ex.: Cytoplasmic streaming.
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Reproduction
Producing individuals of own kind is a characteristic feature of living organisms. Life is perpetuated by this process of one organism reproducing another organism of its kind. Reproduction follows the rule: ‘like begets like’. Reproduction is of three types. Living organisms adopt any or all of the three methods. Sexual reproduction is seen in majority of higher plants and animals. It involves the formation of gametes that fuse together to form a new cell called zygote. The zygote gives rise to new individual.
Asexual reproduction does not involve the formation of gametes and thus, is a kind of reproduction in which offsprings are formed from a single organism. Vegetative reproduction is a special kind of asexual reproduction is a special kind of asexual reproduction in which a large part of the plant body develops into a new plant. Because of reproduction, all organisms exhibit a life cycle. The connecting link at the molecular level between the parents and offsprings is the genetic material (Deoxy-ribo Nucleic Acid) DNA. DNA maintains and perpetuates life.
Growth
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Living organisms grow from within by a process called intussusception. After birth, an organism grows following the information received from the parents through DNA. But growth may also occur in an organ or even within a cell due to increase in protoplasm.
The seven life processes described above are an absolute requirement for a thing to be treated as alive. Besides the seven life process, a few other characteristics are also considered as life process. They are the followings:
(i) Life cycle
(ii) Death
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(iii) Adaptations
(iv) Evolution
(v) Homeostasis
The above process are briefly defined below:
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(i) Life cycle:
Every organism after its birth, grows, matures, reproduces and ultimately dies. But prior to death, reproduction results in new organisms that again enter into the cycle of growth, maturation and reproduction.
(ii) Death:
Every organism dies. Thus, death can be considered as a characteristics of life. Death may be programmed in the DNA or it may be due to an accident or disease.
(iii) Adaptations:
Only living organisms have the capacity to adapt to the surroundings. Adaptation is a necessary feature for survival.
(iv) Evolution:
One of the important characteristics of living organisms is the capacity to evolve. By responding to the changes in the environment, an organisms shows long term adaptation that may contribute to the formation of new species and thus, to the process of evolution.
(v) Homeostasis:
Cells, tissues, organs of living organisms have an inherent capacity to maintain homeostasis, i.e., balance between input and output of matter and energy. Such a balance is maintained at the level of organism, population and community.
Living organisms exhibit the above life processes to a greater or lesser extent. Plants being living organisms, also exhibit the above living characters.