Biology Today — January 2018

On the basis

of flowering

frequency

Monocarpic

These plants flower and fruit only once in their lifetime. All annual and

biennial plants are monocarpic. However, some perennial plants are

also monocarpic, e.g., bamboo and Agave.

Polycarpic

These plants bear flowers and fruits

repeatedly after attaining maturity, e.g.,

Acacia, Eucalyptus, Mangifera, etc.

Annuals

Plants which complete their life cycle from germination

through flowering and seed production to death in a

single year or less. Examples include cereals, grains,

legumes, etc.

Biennials

Plants which complete their life cycle in two years.

Flowering usually occurs during the second year, after

a year of vegetative growth. Beets and carrots are

biennials.

Perennials

Plants that live for few

years to several hundred

years, e.g., trees like neem,

Ficus, etc.

On the basis of life span

On the basis of habitat

(Natural home of organisms)

Hydrophytes

Plants growing in aquatic habitats. Most of them are found in freshwater, e.g.,

Wolffia, Lemna, Nelumbo, etc. However, few are marine, e.g., Zostera, Thalassia.

Lithophytes

Plants growing over rocky substrata, e.g., many

algae, Nostoc, ferns, etc.

Mesophytes

Plants of moist habitats like

tropical rainforests, crop plants,

etc., e.g., sunflower, Artocarpus.

Xerophytes

Plants growing in dry habitats,

e.g., Capparis, Acacia. They may

be succulents, e.g., Euphorbia.

Psammophytes

Plants occur in sandy

habitats.

Halophytes

Plants of saline habitats that may be terrestrial, e.g., Salsola or

mangrove plants (found in marshy habitats along sea shore), e.g.,

Rhizophora.

PARTS OF A FLOWERING PLANT

• Plant axis is differentiated into above ground

shoot system and underground root system.

The different structures borne on the plant axis

are called organs. There are two types of plant

organs, vegetative and reproductive. Root, stem

and leaves are vegetative organs while flowers,

fruits and seeds are reproductive organs.

MORPHOLOGY OF ROOT

• The root is typically a non-green underground

descending portion of the plant axis which gives

rise to similar types of endogenous lateral branches

and does not possess nodes and internodes. It is

positively geotropic, positively hydrotropic and

negatively phototropic.

Parts of Root

• A typical root possesses following parts:

Flower

Fruit

Stem

Leaf

Bud

Primary root

Root system

Shoot system

Secondary root

Node

Internode

Fig.: Parts of a flowering plant