Habitat

Habitat is the natural home of an organism. Angiosperms are both terrestrial and aquatic. Aquatic habitats may be fresh water or marine. Only two angiosperms are marine, e.g., Zostera and Thalassia. In many aquatic plants roots are reduced or absent (e.g., Utricularia, Wolffia, Ceratophyllum). Plants of damp and shady places are called hygrophytes, e.g., elephant grass (Typha elephantia). Plants growing in marshy areas or swampy places are called mangrove plants, e.g., Rhizophora, Avicennia, etc.

• Terrestrial plants are of two main types; mesophytes and xerophytes. Mesophytes are plants that live in wide range but are not adapted to live either in very dry or very wet conditions. They form natural dense growth which may appear as grassland or forest. Vegetation occurring at high mountains is called alpine vegetation.
• Plants adapted to grow in dry habitats are called xerophytes, e.g., cacti, Euphorbia, etc. Some of the xerophytes store water and mucilage, and are called succulents, e.g., Euphorbia, Opuntia, etc. Other xerophytes develop spines that reduce transpiration and provide protection against browsing animals, e.g., Alhagi, Zizyphus, Acacia, Argemone, Lantana, etc.

HABITS

• On the basis of longevity or life span plants are of following types:
• Annuals : They flower, shed seeds, senesce and die in one season, e.g., rice, wheat, gram, groundnut, etc.
• Biennials : They grow in one season and set seeds in the next season with a rest period during winter in between, e.g., sugar beet, henbane, carrot, radish, etc.
• Perennials : Such plants survive for several years, e.g., Canna, Mango, Agave, Bambusa, Eucalyptus, etc.
• Annuals and biennials are monocarpic, i.e., flower and fruit only once in life. Usually perennial plants are polycarpic. However, some perennial plants are also monocarpic, e.g., Agave americana, Bambusa tulda, Melocanna bambusoides.

According to texture, height, growth and duration of stem, plants are:

• Herbs : They are small plants with soft stem which normally grow to a height of less than 2m. They may be annual (e.g., Butter-cup), biennials (e.g., Henbane) and perennial (e.g., Canna, Banana, etc).
• Shrubs :They are perennial plants with medium height and woody stem having several branches of equal height, e.g., Capparis, Rosa, Jasminium, etc. Shrubs are also called bushes.
• Trees: Tall perennial plants with a thick woody main stem or trunk are called trees. They may be of following types:

➢ Caudex : Unbranched trunk with crown of leaves at the apex, e.g., Date palm, Coconut, etc.

➢ Excurrent : Lateral branches arising from trunk give a cone like appearance, e.g., Eucalyptus, Polyalthia, etc.

➢ Deliquescent : The trunk disappears after sometime and a number of large branches form a dome shaped crown, e.g., Mango, Dalbergia, Ficus, etc.

• Trailers : Plants spread on the ground without rooting at intervals, e.g., Euphorbia prostrata, Tribulus, etc.
• Creepers : Plants spread on the ground, rooting at intervals, e.g., Strawberry, grass, etc.
• Twiners : Weak stemmed plants where the stem coils or twines around an upright support, e.g., Railway creeper (Ipomoea carica), Rangoon creeper (Quisqualis). etc.
• Climbers : Weak stemmed plants, which climb up an upright support by special clinging or clasping structures like tendrils (e.g., Passiflora suberosa), roots (e.g., Piper betle), hooks (e.g., Bignonia unguis-cati), etc.
• Lianas : Woody climbers, found in tropical evergreen forests, e.g., Bauhinia, Hiptage, etc.
• Epiphytes : They are plants that live on other plants for space, e.g., Vanda.