1. Roots are totally absent in Wolffia and Salvinia or poorly developed in Hydrilla or well developed in Ranunculus.
2. The root caps are replaced by root pockets. Example: Eichhornia

(a) Latitude
(b) Altitude
(c) Direction of mountain and
(d) Steepness of mountain.

(a) Halophytes: Plants living in saline soils.
(b) Chasmophytes: Plants living in rocky crevices.
(c) Cryophytes: Plants living in ice surface.
(d) Psammophytes: Plants living in sandy soils

Euryhaline: Organisms which can live in water with wide range of salinity. Examples: Marine algae and marina angiosperms.
Stenohaline: Organisms which can withstand only small range of salinity. Example: Plants of estuaries.

The environment (surrounding) includes physical, chemical and biological components. When a component surrounding an organism affects the life of an organism, it becomes a factor. All such factors together are called environmental factors or ecological factors.

An ecological niche refers to an organism's place in the biotic environment and its functional role in an ecosystem.

1. Sometimes, ants take their shelter on some trees such as mango, litchi, jamun, acacia etc.
2. These ants act as body guards of the plants against any disturbing agent and the plants in turn provide food and shelter to these ants.
3. This phenomenon is known as Myrmecophily.
Example: Acacia and, Acacia ants.

1. The outer bark of trees which extends to the last formed periderm is called rhytidome.
2. It is composed of multiple layers of suberized periderm, cortical & phloem tissues.
3. It protects the stem against fire, water loss, invasion of insects & prevents infection by microorganisms.

Submerged plants are unable to obtain full illumination because a lot of sunlight is absorbed by overlying layers of water this is not the case for exposed floating plants that receive sunlight directly.

1. Lichen is a mutual association of an alga & a fungus.
2. It is an interaction between two species of organisms in which both are benefitted from the obligate association.

Certain plants can also be used to remove cadmium from contaminated soil, this is known as phytoremediation.
Example: Eichhornia

1. It deals with the study of environment in relation to organisms.
2. It can be studied by considering individual organisms, population, community, biome or biosphere and their environment.

Anatomical adaptations:
1. Epidermal cells of stem is heavily cutinized, almost squarish and are filled with oil and tannins.
2. 'Star' shaped sclereids and 'H' shaped heavy thickened spicules that provide mechanical strength to cortex are present in the stem.
3. The leaves may be dorsiventral or isobilateral with salt secreting glands.

The plants which are found growing on other plants without harming them are called epiphytes. They are commonly found in tropical rain forest.
The epiphytic higher plant (Orchids) gets its nutrients and water from the atmosphere with the help of their hygroscopic roots which contain special type of spongy tissue called Velamen. So it prepares its own food and does not depend on the host. They use the host plant only for support and does not harm.

1. Ground fire - Which is flame less and subterranean.
2. Surface fire - Which consumes the herbs and shrubs.
3. Crown fire - Which burns the forest canopy.

S. No.	Habitat	Niche
1	A specific physical space occupied by an organism (species).	A functional space occupied by an organism in the same eco-system.
2	Same habitat may be shared by many organisms (species).	A single niche is occupied by a single species.
3	Habitat specificity is exhibited by organism.	Organisms may change their niche with time and season

(i) Ground fire: Which is flameless and subterranean.
(ii) Surface fire: Which consumes the herbs and shrubs.
(iii) Crown fire: Which burns the forest canopy.
Effects of fire
1. Fire has a direct lethal effect on plants.
2. Burning scars are the suitable places for the entry of parasitic fungi and insects.
3. It brings out the alteration of light, rainfall, nutrient cycle, fertility of soil, pH, soil flora and fauna.
4. Some fungi which grow in soil of burnt areas called pyrophilous.
Example: Pyronema confluens

(a) Life cycle is completed within a short period (Ephemerals)
(b) In succulents the stem possess a water storage region
(c) Root hairs & root caps are also well developed

1. Cuscuta is a total stem parasite of the host plant Acacia, Duranta and many other plants Cuscuta even gets flower inducing hormone from its host Plant.
2. Balanophora, orobanche and Refflesia are the total root parasites found on higher plants.

The differences between habitat and niche are as follows.

S. No	Habitat	Niche
1	A specific physical space occupied by an organism (species).	A functional space occupied by an organism in the same eco-system
2	Same habitat may be shared by many organisms (species).	A single niche is occupied by a single species.
3	Habitat specificity is exhibited by organism.	Organisms may change their niche with time and season

Morphological adaptations:
Root system is extensively developed. These roots may be of two types. They are Clinging roots and Aerial roots.
Clinging roots fix the epiphytes firmly on the surface of the supporting objects.
Aerial roots are green coloured roots which may hang downwardly and absorb moisture from the atmosphere with the help of a spongy tissue called velamen.
1. Stem of some epiphytes are succulent and develop pseudo bulb or tuber.
2. Generally the leaves are lesser in number and may be fleshy and leathery.
3. Myrmecophily is a common occurrence in the epiphytic vegetation to prevent the predators
4. The fruits and seeds are very small and usually dispersed by wind, insects and birds.

The important edaphic factors which affect vegetation are as follows:
1. Soil moisture: Plants absorbs rain water and moisture directly from the air.
2. Soil water: Soil water is more important than any other ecological factors affecting the distribution of plants. Rain is the main source of soil water. Capillary water held between pore spaces of soil particles and angles between them is the most important form of water available to the plants.
3. Soil reactions: Soil may be acidic or alkaline or neutral in their reaction. pH value of the soil solution determines the availability of plant nutrients. The best pH range of the soil for cultivation of crop plants is 5.5 to 6.8.
4. Soil nutrients: Soil fertility and productivity is the ability of soil to provide all essential plant nutrients such as minerals and organic nutrients in the form of ions.
5. Soil temperature: Soil temperature of an area plays an important role in determining the geographical distribution of plants. Low temperature reduces use of water and solute absorption by roots.
6. Soil atmosphere: The spaces left between soil particles are called pore spaces which contains oxygen and carbon-di-oxide.
7. Soil organisms: Many organisms existing in the soil like bacteria, fungi, algae, protozoans, nematodes, insects and earthworms, etc., are called soil organisms.

Advantages of seed dispersal:
1. Seeds escape from mortality near the parent plants due to predation by animals or getting diseases and also avoiding competition.
2. Dispersal also gives a chance to occupy favourable sites for growth.
3. It is an important process in the movement of plant genes particularly this is the only method available for self-fertilized flowers and maternally transmitted genes in outcrossing plants.
4. Seed dispersal by animals help in conservation of many species even in human altered ecosystems.
5. Understanding of fruits and seed dispersal acts as a key for proper functioning and establishment of many ecosystems from deserts to evergreen forests and also for the maintenance of biodiversity conservation and restoration of ecosystems.
Seed ball:
1. It is an ancient Japanese technique of encasing seeds in a mixture of clay and soil humus (also in cow dung).
2. It also includes the soil humus scattering them on to the suitable; not planting of trees manually.
3. This method is suitable for barren and degraded lands for tree regeneration and vegetation before monsoon period where the suitable dispersal agents become rare.

Morphological adaptations
1. The temperate halophytes are herbaceous but the tropical halophytes are mostly bushy.
2. In addition to the normal roots, many stilt roots are developed.
3. A special type of negatively geotropic roots called pneumatophores with pneumathodes to get sufficient aeration are also present. They are called breathing roots. Example: Avicennia.
4. Presence of thick cuticle on the aerial parts of the plant body.
5. Leaves are thick, entire, succulent and glossy. Some species are aphyllous (without leaves).

The plants which are living in dry or xeric condition are known as Xerophytes.
Xerophytic habitat can be of two different types They are:
(a) physical dryness: In these habitats, soil has a little amount of water due to the inability of the soil to hold water because of low rainfall.
(b) physiological dryness: In these habitats, water is sufficiently present but plants are unable to absorb it because of the absence of capillary spaces. Example: Plants in salty and acidic soil.
Based on adaptive characters xerophytes are classified into three categories. They are Ephemerals, Succulents and Non - succulent plants.

(i) Ephemerals: These are also called drought escapers or drought evaders. These plants complete their life cycle within a short period (single season). These are not true xerophytes. Examples: Argemone, Mollugo, Tribulus and Tephrosia.
(ii) Succulents: These are also called drought enduring plants. These plants store water in their plant parts during the dry period. These plants develop certain adaptive characters to resist extreme ,drought conditions. Examples: Opuntia, Aloe, Bryophyllum and Begonia.
(iii) Non succulents: These are also called drought resistant plants ( true xerophytes). They face both external and internal dryness. They have many adaptations to resist dry conditions. Examples: Casuarina, Nerium, Zizyphus and Acacia.

i. Free floating hydrophytes: These plants float freely on the surface of water. They remain in contact with water and air, but not with soil. Examples: Eichhornia, Pistia and Wolffia (smallest flowering plant).
ii. Rooted floating hydrophytes: In these plants, the roots are fixed in mud, but their leaves and flowers are floating on the surface of water. These plants are in contact with soil, water and air. Examples: Nelumbo, Nymphaea, Potomogeton and Marsilea. Lotus seeds showing highest longevity in plant kingdom.
iii. Submerged floating hydrophytes: These plants are completely submerged in water and not in contact with soil and air. Examples: Ceratophyllum and Utricularia.
iv. Rooted-submerged hydrophytes: These plants are completely submerged in water and rooted in soil and not in contact with air. Examples: Hydrilla, Vallisneria and Isoetes.
v. Amphibious hydrophytes (Rooted emergent hydrophytes): These plants are adapted to both aquatic and terrestrial modes of life. They grow in shallow water. Examples: Ranunculus, Typha and Sagittaria.

1. In many species of fig trees, there is a one-to one relationship with the pollinator species of wasp. It means that a given fig species can be pollinated only by its 'partner' wasp species & no other species.
2. The female wasp uses the fruit not only as an oviposition (egg, laying) site but uses the developing seeds within the fruit for nourishing its larvae.
3. The wasp pollinates the fig inflorescence while searching for suitable egg-laying sites.
4. In return for the favour of pollination the fig offers the wasp, some of its developing seeds, as food for the developing wasp larvae.
5. The relationship that operates here is co-evolution.