divercity of plants

22 September/ 09


THE DIVERSITY OF PLANTS

The plant kingdom is the second largest kingdom ( has the most species) after the animal kingdom. There are around 200,000 known species of plant.

We have seen a non-scientific classification of plants according to their shape. In order to classify them scientifically we have to use the criteria.

Plants are either vascular or non-vascular. This means that they either have or don't have a tube like structure which transports water, nutrients and mineral salts up the steams.
Some plants produce flowers and some do not.
some plants produce fruit and others do not.
Using these three criteria we can divide the plant kingdom into four large groups:


1.Bryophytes or mosses: commonly called mosses and liverworts, they are the smallest and simplest of all the plants. They have no fruit and are non-vascular. They depend on the presence of water of their survival and life in damp places.
2.Pterydophyta: this is a group of ferns. They are medium-sized vascular plants but they have no flower or fruit. They have large leaves are divided up into different sections. They also live and damp places.
3.Gymnosperms: this plants are vascular and they have flowers but not fruit. Most of them are threes or bushes like the pine tree and juniper bush or cypress. The largest tress in the world, the sequoias, belong to this group.
4.Angiosperms: these-plants are vascular, they have flower and fruit. This group of plants is the most varied because it includes grasses, bushes and trees. Some examples are, poppies, roses, rock-rose, thyme, holm cak, chestnut etc.

NUTRITION IN PLANT

FOOD FOR PLANTS

plants are producers which means that they produce their own food. In order to do this they need to absorb substances from the soil and the air and to transform them. This process has the following steps

1.plants absorb water and mineral salts from the soil plants need to absorb to their root . Various different mineral salts are dissolve in the water. The mixture of mineral salt and water which is up sort, by the plant is noun us raw sap.
2.The steamtransport the raw sap of the leaves, the rous sap moves up wards from the roots to the steam. After these if caries on up words through the vanes in ther steen, until it riches the leaves.
3.The raw up is transformed in the leabes, the fundamental proces of nutrition takes places in the leaves. This proces is called photosintesis.
4.The elaborated sap is distributed throughtout the plant finaly the nutrients containet in the elaborated sap are distributed throughtout the plant. It richers all the cells throught the vessels.



PLANTS RESPIRATION

plants breathe just as animals do. Their leaves takes oxygen from the airand release carbon dioxyde . Howeber, during the proces of photosintesis they take in carbon dioxide and realice oxygen. This proces of respiration involbes the taking and the relasing of glases bat in the reverse order as happends during nutrition. During the proces of nutrition the plant takes in carbon dioxide and releases oxygen.

During the day time the two proceses, respiration and nutririon are simultaneous. Howeber at night they are not.
.
During the day time plants breathe and carry out the proces of photosisntesis at night plants do not photosintesi but they do beathe