Life Span
The time between an organism’s birth and death is referred to as its life span. It is a specific trait and it is as long as several thousand years and as short as a few minutes. The life span of mango is about 200 years and the life span of peepal is 2500 years.No individual lives forever but an exception is a single-celled organism i.e they are immortal.
The life span of a few organisms
| S.NO. | Organism | Life-span |
| 01 | Mayfly | One day |
| 02 | Wheat | 5 months |
| 03 | Rabbit | 13 years |
| 04 | Monkey | 26 years |
| 05 | Dog | 20-30 years |
| 06 | Cat | 35-40 years |
| 07 | Horse | 60 years |
| 08 | Elephant | 65 years |
| 09 | Man | 60.4 years |
| 10 | Parrot | 140 years |
| 11 | Banyan tree | 200 years |
| 12 | Peepal | 2000-3000 years |
| 13 | Crow | 140 years |
| 14 | Mango | 200 years |
Reproduction
It is the biological process by which an organism produces young or children that are genetically identical to itself. Birth, growth, and death occur in a continuous cycle, allowing species to survive generation after generation.
Reproduction performs the following functions
1. Maintains life on the Earth
2. Enables continuity of the species
3. Creates variations among populations
Several factors that determine how an organism reproduces are
1. The organism’s habitat
2. Its internal physiology
3. Environmental conditions
Reproduction Types
Based on the participation of one organism/parent or two, reproduction can be categorized into two types i.e. Asexual and Sexual.
Asexual reproduction
Asexual reproduction is the creation of offspring by a single parent without the development and fusing of gametes. It involves only mitotic cell division and meiosis does not occur in asexual reproduction.
Features of Asexual Reproduction
1. The involvement of single parents is why it is called uniparental.
2. It can happen with or without the production of gametes. But gametic fusion i.e. fertilization is absent.
3. The chromosomes are inherited from single-parent i.e. the offspring produced are exact copies of each other as well as they are exact copies of parents. Thus organisms that are morphologically as well as genetically similar are called a clone.
4. In asexual reproduction, the clone is common in a single-celled organism as well as plants and animals that show simple body organization e,g Monera (bacteria), Protista (Amoeba), Algae, Fungi, etc. When it is shown by higher plants it is called vegetative propagation.
5. It is a simple and fast process.
Asexual Reproduction
Binary Fission: The division of the parent cell into two small, virtually equal-sized daughter individuals is known as binary fission.
Binary fission can be classified into the following categories, depending on the plane of division:
(i)Simple binary fission: Divisions can occur through any plane e,g Amoeba
(ii) Longitudinal binary fission: The plane of fission runs parallel to the organism’s longitudinal axis. e,g Euglena
(iii) Transverse binary fission: The plane of division runs parallel to the individual’s transverse axis. e,g Bacteria, Paramecium, Diatoms.
Budding
It is the development of an individual from a tiny projection on the parent body termed a bud. Budding can be of two forms, depending on where the bud appears.
(i)Simple budding: In yeast, the division is unequal, resulting in little buds that remain connected to the parent cell at first, later separating and maturing into a new yeast organism.
(ii)Budding or sporulation is also shown by oidia of Rhizopus.
Spore formation
These are mitospores or asexually produced spores, formed to overcome unfavorable conditions. Lower fungi are more likely to produce spores. Various organisms contain the following sorts of spores:
(i) Zoospores: Zoospores have 1-2 flagella that are born anterior or posterior. They are motile spores with flagella. The flagella help zoospore dissemination by allowing them to swim in watery environments. e,g Chlamydomonas, Albugo, Phytophthora, etc.
(ii) Conidia: They are non-motile, exogenous spores, that develop through constriction on the tips of hyphae e,g Penicillium, Aspergillus, etc,
Vegetative Propagation
It is the formation of new plants from their vegetative parts like roots, stems, leaves, etc. the somatic parts i.e. Root, Stem, and Leaves after detachment that form new individuals are known as vegetative propagules.
Vegetative propagation
1. Natural Vegetative propagation
2. Artificial vegetative propagation
1. Natural Vegetative propagation: In Natural methods, some of the plants get detached from the body of the mother plant and grow into an independent plant. This can happen by the subsequent vegetative propagules
A.Root: The buds present on the roots grow into leafy shoots called slips above the ground and adventitious roots at their bases. Each slip gives rise to a new plant, e,g Sweet potato, Dahlia, Dalbergia sisso, Guava, etc,
Underground stems
Underground modified stems possess buds that grow into new plants. The following are its various types:
(i) Rhizomes: Rhizomes are a type of vegetative reproduction that can perennate in poor conditions and produce new aerial shoots in favorable conditions.
It includes Ginger, Turmeric, Banana, Lotus, etc.
(ii) Tubers: They are underground stem branches with many buds that have been changed. Each potato eye is a bud that develops into a new potato plant.
(iii) Bulbs: The Bulbs are highly reduced underground stems. The stem is reduced in the form of a disc that can be slightly conical, leaves present in the form of the whorl. E,g Onion, Garlic, Lilies, etc
(iv) Corms: These are highly condensed and specialized underground stems that bear many buds. The buds are protected by scaly leaves. As favorable conditions will come this bud will sprout and form new plants. E,g Zaminkand, Crocus etc.
Sub-Aerial stem or Creeping stem
Vegetative propagation through creeping stems are given below
(i) Runners: It is a slender, prostrate aerial stem that creeps horizontally on the surface of the soil. They are modified stems, that produce adventitious roots at nodes. Each node give rise to an aerial shoot that becomes a new plant e,g Doob grass (Cynodon dactylon), Oxalis, Creeping buttercup, etc,
(ii) Sucker: A sucker is a sub-aerial branch that arises from the basal underground part of the main stem. It grows horizontally beneath the soil’s surface at first but then slants upward, forming a leafy stalk. These shoots become independent when suckers break away from the parent plants. E,g Mint, Banana, etc,
(iii) Offsets: The Horizontal stem is present. Due to the presence of a single internode, it is also called a single internode Runner. It is very much similar to the runner but it is aquatic modification. It has swollen stem because it has aerenchyma that helps the plant to float. From this stem arise a transverse branch. The branch is also swollen and will arise in all directions. E,g Pistia, Euchanaria (water Hyacinth).
(iv) Stolons: These are arching runners with little plantlets at their nodes that cross over small barriers. The branch arises from the underground part of the stem and then goes aerial and then touches the ground and again there grows stem and aerial and so on Example, Strawberry, Jasmine, etc,
D. Aerial Stems: Aerial modified stems of cacti produce new plants when the stem segments fall on the ground. These act as the means of vegetative propagation e,g Opuntia, These are used for vegetative propagation.
E. Leaves: Some plants develop adventitious buds on their leaves and it is known as Foliar bud. It can be positioned in two ways, It can be present on margins and present at the tip region. E,g Bryophyllum, In this the leaf contains notches that have bud and bud can sprout forming a new plant.
F. Bulbils: They are larger-sized fleshy buds formed during favorable conditions and form new individuals. They work like reproductive structures but in unfavorable conditions, they will act like resting structures. These resting structures are known as perenating structures e,g Chlorophytum, Oxalis, Lily, Agave
Artificial vegetative propagation
Humans have taken the advantage of Natural Vegetative propagation and have propagated plants vegetatively by using the specialized parts. It includes the following methods.
1. Layering
2. Grafting
3. Cuttings
Layering
The process of inducing root formation in the stem while it is still attached to the parent plant it is known as Layering. In many fruit and ornamental plants, layers of several types are used for vegetative propagation. It is of two types
A. Soil layering B. Air Layering
A. Soil layering: It is found in those plants where a soft flexible branch near the soil surface is present. It is of the following types
(i) Tip-Layering: It is found in blackberry and Gooseberry. The stem branch is soft and is present near the soil surface. This stem branch is packed into the soil. The leaves of the packed part will be removed from it i.e. defoliated and the tip will remain upright. The branch that bent into the soil is known as the Layer. This branch should be one year old. The lower part of the layer is cut. In this, there will be the formation of healing hormone i.e.Traumatic acid i.e (Auxin). This Auxin results in cell division, it also results in root initiation thus also called Rootone or RSH i.e. Root Setting Hormone. Due to traumatic acid, there is the formation of adventitious roots thus it leads to the formation of the shoot system.
(ii) Serpentine Layering: In this process, the lower branch of the plant that is soft and flexible is bent inside the soil at several places. This branch should be one year old and defoliated. The part that is inside the soil is given cuts. Thus the new plant is ready. In serpentine Layering, several plants are formed. It is practiced in Clematis, Pothos (money plant).
(iii) Trench Layering: In this process, a long pit is formed i.e., Trench. The layer is placed horizontally. At the intervals, cuts are given. Due to cuts roots are formed and where buds are present sprout and result in the formation of the shoot system. It is practiced in mulberry, Walnut, etc,
(iv) Mould Layering: In this process, The buds present will sprout and form several shoot systems. The below part is covered with soil. the several shoots start to develop root system e,g Apple, Pear, Cherry, Jasmine
B. Air Layering: This technique is usually employed in those plants where stem branches can not be bent to the soil. From the lower part of the woody branch, the bark is removed in the form of a ring from 3-5 cm in length. When the bark is removed vascular cambium is exposed. Then this region is covered with the help of grafting clay. Now there is the formation of adventitious root it will take 2-3 months. we know the shoot system is already present we develop a root system. Thus the new plant is formed. E,g Lemon, Orange, Guava, Pomegranate, China rose.
Grafting
The process of joining together parts of two different plants in such a way that they live as one plant is called Grafting. A part of the plant is inserted into another plant of the same species or sometimes compatible plants of different species or genera.it results in combining superior features of different plants in one plant. the Graft involves two plants of which one rooted in the soil known as Stock and the other grafted on it is called Scion. The stock and the scion become united and grow as one plant.
Grafting is of the following types
A. Whip Grafting
B. Wedge grafting
C. Crown grafting
D. Approach Grafting
E. Bud Grafting
A. Whip Grafting: It is also called Tongue grafting. In this type of Grafting, stock and scion are almost of the same diameter about 1 to 1.5 cm. The cut is oblique slopping. All buds are removed from the stock but retained on the scion.
B. Wedge grafting: In wedge grafting, stock and scion are of the nearly same diameter. A V-shaped notch is given in the stock, while the scion is cut like a wedge.
C. Crown Grafting: In crown grafting Thus many scions are grafted on a single stock. The lower ends of the scion are cut into long wedges and are inserted into the cute on the stock. They are then tied firmly and the wound is sealed with grafting wax. In the Rose garden in one plant different types of flowers grow on the same plant. It is only possible by crown grafting.
D. Approach Grafting: In this joining of plants is done then cutting. In both, the plant’s bark is removed at the same level in the form of slices. Thus removal of bark will expose cambium meristem. Then press it and bind it after some time they join. Now cut that part that is not used and cut above the graft and below the scion in stock and scion respectively.
E. Bud Grafting: In bud grafting the scion consists of only a single bud accompanied with a portion of the living tissue. A T-shaped incision is made in the bark of the stock, the bark is gently raised on edges, and a scion is inserted into the incision. It is then firmly fastened with strings. It is known as T-bidding. The bud germinates after some time and becomes part of the new plant. Example Roses, Peaches, etc Sometimes instead of a T-shaped or H-shaped cut in the stock, a square patch of bark is removed. It is replaced by another bark of the same shape and size along with a bud. This is called Patch budding.
Cuttings
Any part of the plant (Root, Stem, or Leaf) that produces roots when put in the soil and eventually gives rise to a plant exactly similar to the parent plant is known as cutting. A cutting must essentially have primary meristems. It is of the following types
(i) Root cuttings: This method is often used for propagating Guava, Apple, Pear, Plum, Cherry, Sweet potato, etc.
(ii) Stem cuttings: The stem cuttings are used to propagate both herbaceous and woody plants. The stem cuttings made from the soft non-lignified parts of the woody plants are known as softwood cuttings. Rose, blueberry, etc can be propagated by softwood cuttings. Woody trees such as mango, citrus, guava, litchi, ficus, etc are propagated by stem cuttings taken from mature wood of the current year.