- Herb is defined as a plant whose stem is always green and tender with height of not more than 1 meter
- Shrub is defined as a woody perennial plant differing from a perennial herb in its persistent, and woody stem. It differs from- a tree in its long stature and its habit of branching from the base. Not more than 6 meters in height.
- Tree is defined as a large woody perennial plant having a single well defined stem with more or less definite crown.
- Parasites-An organism that draws a part or whole of its nourishment from another living organism(not from soil). They grow on some living plant called host and penetrate their sucking roots, called haustoria, into the host plants.
- Epiphytes only take the help of the host plant in getting access to light. Their roots perform two functions. While changing roots establish the plant on the branches of the host plant, aerial roots draw moisture from the air. Eg. Vanda-Climbers plant growing on the host plant but not nourished by the host plant.
EFFECT OF ABIOTI C COMPONENTS ON PLANTS
- Intensity of light on growth of plants
- Extremely high intensity favours root growth than shoot growth which results in increased transpiration, short stem, smaller thicker leaves, low intensity of light retards growth, flowering arid fruiting.
- Out of 7 colours in the visible part of spectrum, only red and blue are effective in photosynthesis.
- Plant grown in blue light are small, red light results in elongation of cells results in etiolated plants
Effect of frost on plants
- Killing of young plants frost chills the soil resulting in freezing the soil moisture. The plants growing in such soil, get exposed to direct sun light in the morning, they are killed due to increased transpiration when their roots are unable to supply moisture. This is the main reason for innumerable death of sal seedlings.
- Death of plants due to damage to cells - As a result of frost, water in the intercellular spaces of the plant gets. Frozen into ice which withdraws water from the interior of the cells. This results in increasing concentration of salts and dehydration of cells.
- Thus coagulation and precipitation of the cell colloid results in death of plant. Leads to Formation of canker.
Effect of temperature on plants
Excessive high temperature results in death of plant due to coagulation of protoplasmic proteins.
- These plants are specialised in trapping insects and are popularly known as insectivorous plants
- Insectivorous plants can broadly be divided into active and passive types based on their method of trapping their prey
- The active ones can close their leaf traps the moment insects land on them.
- The passive plants have a pitfall' mechanism, having some kind of jar or pitcher- like structure into which the insect slips and falls, to eventually be digested.
(i) Why do they hunt despite having normal roots and photosynthetic leaves?
- These plants are usually associated with rain-washed, nutrient-poor soils, or wet and acidic areas that are ill-drained.
- Wetlands are acidic due to anaerobic conditions, which cause partial decomposition of organic matter releasing acidic compounds into the surroundings.
- Most microorganisms necessary for complete decomposition of organic matter cannot Survive in such poorly oxygenated conditions. Normal plants find it difficult to survive in such nutrient poor habitats.
- The hunter plants are successful in such places because they supplement their photo synthetic food production by trapping insects and digesting their nitrogen rich bodies.
(ii) The Indian Hunters
Insectivorous plants of India belong mainly to three families:
- Droseraceae (3 species),
- Nepenthaceae (1 species)and
- Lentibulariaceae (36 species)
(iii) Family: Droseraceae:
This includes 4 genera of which 2, namely Drosera and Aldrovanda, occur in India
(iv) Family Nepenthaceae
- It consists of a single genus Nepenthes having about 70 species distributed throughout the tropical Old World. The members of the family are commonly known as ’pitcher plants’ because their leaves bearjar-like structures.
- Distribution It is confined to the high rainfall hills and plateaus of north-eastern region, at altitudes ranging from 1.00-1500 rn, particularly in Garo, Khasi and Jaintia hills of Meghalaya
(v) Family: Lentibulariaceae:
It have 4 genera, of which Utricularia and Pinguicula, occur in India
(vi) Medicinal properties
- Drosera are capable of curdling milk, its bruised leaves are applied on blisters, used for dyeing silk.
- Nepenthes in local medicine to treat cholera patients, the liquid inside the pitcher is useful for urinary troubles, it is also used as eye drops.
Utricularia is useful aga inst cough, for dressing of wounds, as a remedy for urinary disease.
- In India, species like Drosera peltata, Aldrovanda vesiculosa and Nepenthes khasiana have been - included in the Red Data Bookas endangered plants
(vii) INVASIVE ALIEN SPECIES
Alien species that threaten native plants and animals or other aspects of biodiversity are called alien invasive species
- Loss of Biodiversity
- Decline of Native Species (Endemics)
- Habitat Loss
- Introduced pathogens reduce crop and stock yields
- Degradation of marine and freshwater ecosystems
- This biological invasion constitutes the greatest threat to biodiversity
SOME INVASIVE ALIEIN FLORA OF INDIA
(i) Needle Bush
- Nativity: Trop. South
- Distribution in India: A shrub or small tree
(ii) Black Wattle
- Nativity: South East Australia
- 'Distribution in India: Western Ghats
- Remarks: Introduced for afforestation in Western Ghats. Regenerates rapidly after fire and forms dense thickets. It is distributed in forests and grazing lands in high altitude areas.
(iii) Goat weed
- Nativity: Trop. America
- Distribution in India: Throughout Remarks: Aggressive colonizer. Troublesome weed in gardens, cultivated fields and forests
(i) Beddomes Cycad/ Perita 1 Konciaitha.
- Eastern Peninsular India.
- Uses: The male cones of the plant are used by local herbalists as a cure for rheumatoid arthritis and muscle pains.
- Fire resistant property is also there.
(ii) Blue vanda / Autumn Ladies Tresses Orchid
- Distribution: Assam, Arunachal Pradesh, Manipur, Meghalaya, Nagaland.
- Vanda is one of the few botanical orchids with blue flowers a property much appreciated for producing interspecific and intergeneric hybrids.
(iii) Kuth /Kustha / Pooshkarmoola /Uplet
- Distribution Kashmir, Himachal Pradesh
- Uses: It is used as an anti-inflammatory drug
(iv) Ladies Slipper Orchid
Uses These types of orchids are mainly used as collector’s items And treat anxiety insomniaa
(v) Red vanda
- Distribution: Manipur, Assam, Andhra Pradesh
- Uses: As a whole orchids are collected to satisfy an ever demanding market of orchid fanciers, especially in Europe, North America and Asia
- Dstribution: Sub Himalayan tract from Punjab eastwards to Nepal, Sikkim, Assam, Eastern & Western Ghats, parts of Central India & in the Andamans.
- Uses It is used for treating various central nervous system disorders.