In this article we will discuss about:- 1. Characters of Vascular Plants 2. Reasons for Dominance and Success of Vascular Plants.
Characters of Vascular Plants:
1. They are those plants which possess conducting or vascular tissues, xylem and phloem. Xylem transports water and minerals while phloem conducts organic food.
2. Vascular plants comprise more than 275,000 living species.
3. They are the most visible green plants around us, so much so that the term plants generally means vascular plants.
4. The plant body is differentiated into true stem, leaves and roots. The roots not only anchor the vascular plants to the soil but also absorb water and minerals from inside the soil. The leaves manufacture organic food by intercepting sunlight and absorbing carbon dioxide from the atmosphere. Stem provides support to leaves and connects the roots with the leaves.
5. On account of anchoring by root and conduction of water, minerals, food, etc. by the vascular tissues, the plants can reach great heights and longevity. Eucalyptus regnans (114 m) and Sequoia sempervirens (111 m) reach a height of more than 100 m. Plants are known to live for more than 6000 years, e.g., Macro-zamia (a gymnosperm, 10,000-12,000 years), Dracaena draco (Dragon Tree, 8000-10,000 years).
6. Vascular plants are adapted to most diverse environments by modification of their organs.
7. Conspicuous stage or plant body is a sporophyte. Gametophyte is always inconspicuous, living either independently or parasitic over the sporophyte.
8. Accessory spores are absent. Multiplication occurs by vegetative propagation and sexual reproduction. Meiosis occurs inside sporangia associated with leaves. The latter are, therefore, also called sporophylls.
9. An embryo stage is present in the life cycle.
Land animals and most fungi directly or indirectly depend upon vascular plants for their sustenance. They are also the source of food, fibres, fuel, furniture, medicines and a score of other items to human beings.
Reasons for Dominance and Success of Vascular Plants:
Vascular plants dominate land. They have clothed this planet green.
The reasons for success and dominance are as follows:
(1) Presence of deep, penetrating and wide-spreading roots which not only anchor the plants but also absorb water and mineral salts from deeper layers of the soil.
(2) Covering of aerial parts with water proof material like cutin in living tissue and suberin in dead corky bark.
(3) Mechanical tissues present to allow them to rise to great heights.
(4) Presence of long distance transport system in the form of vascular tissues.
(5) Modification of structure and physiology has occurred to suit various habitats— desert, rocky terrains, moist areas, acid neutral and alkaline soils, warm or cold areas, etc.
Vascular plants are of two types, pteridophytes and seed plants.