Category Plants & Animals

Everything inside a flower is arranged to make pollination possible. This operation involves the transfer of pollen from the anthers of the stamens to the pistil.

It is very rare, however, that the pollen produced by one flower is used to fertilize the pistil in the same flower. Instead, flowers are designed to obtain pollen from other plants and their flowers. This enables better seeds and fruits to be produced and is known as cross-pollination. Its usefulness was demonstrated by the great naturalist, Charles Darwin, in 1859.

Cross-pollinating flowers occasionally have their pollen waiting on the stamens before the pistil is ready to take it, or the pistil may be ready but the stamens have produced no pollen. Some plants produce flowers with’ stamens only (male flowers) while others produce flowers with only pistils (female flowers). These plants are pollinated with the help of the wind which blows the pollen grains through the air.

Such plants produce huge amounts of pollen because much of it is lost in the air and only a small quantity finally reaches its proper destination.

 

 

Picture Credit : Google

A flower consists, first of all, of a pedicle, or stem, that joins it to the plant. The stem broadens out into a hollow cup known as the receptacle. This is surrounded by green sepals which form the calyx. The flower’s petals grow from the calyx in all kinds of shapes and colours.

At the centre of the flower there is a part that resembles a long necked bottle. This is the pistil. The top of the pistil is called the stigma, the neck is called the style and the bottom, which is wider than the rest, is the ovary. Inside the ovary lie several tiny grains called ovules. Each one of these grains will become a seed. The ovary around the seeds will grow larger and turn into a fruit. The pistil is surrounded by several thread-like filaments, the stamens. At the top of each stamen there is a bag-like structure called the anther which contains the pollen.

 

Picture Credit : Google

Bacteria are tiny organisms that can be seen only through a microscope. They live alone as solitary individuals or in groups that are linked like chains. They vary in shape according to their species.

Bacteria are responsible for many diseases in people, plants and animals. These diseases are infectious because they can be passed on whenever the bacteria move to a new place. In plants, over 150 different species of bacteria cause three main types of disease: vascular, parenchymatous and hyperplasic.

In vascular diseases the bacteria attack the vessels and main channels of a plant. This causes a blockage of vital food supplies and the plant dies.

In parenchymatous diseases, the bacteria attack the active tissues of the plant which then rots and dies.

In hyperplasia, the bacteria cause the cells of the plants to multiply wildly and produce swellings or tumours on the stem, the roots and sometimes even on the leaves.

Plants can also catch serious diseases from viruses. There are many kinds of virus, each different from the other and each capable of causing several disorders. It has been found that viruses are carried from one plant to another by insects. These insects act as carriers by sucking the juices of a diseased plant and then injecting them into a healthy one.

A number of viruses are soilborne and some of these are spread by eelworms that feed on plant roots.

Man, too, can spread viruses by handling diseased plants and then touching healthy ones.

One disorder caused by viruses is dwarfism when the plant is stunted. Other virus infections attack the leaves and make them dried and crumpled or cause blisters on the plant’s tissues.

 

Picture Credit : Google

Some plants are killed by the frost when winter arrives but the seeds they dropped on the ground in the autumn ensure that new plants grow to replace them in the spring. Other plants spread out their leaves and flatten them against the ground in order to obtain whatever warmth is left in the soil. The violet is a plant that does this.

Myrtle and heather allow their upper plant to wither and die, but the lower part of the stem stays alive and produces buds when the growing season comes.

Many other plants escape from the cold weather by hiding under the soil. These plants are tubers, bulbs and roots which have stored up all the food they need. When the warm weather returns they are ready to push out green leaves and new buds.

Sometimes mechanical means are used to protect plants from frost. In regions where citrus fruits are grown oil heaters, called smudge pots, are placed in the groves and huge fans are also used to keep the air moving and prevent the cold air from settling on the fruit trees.

 

Picture Credit : Google

There are some seventy different varieties of Nepenthe, most of which grow in the tropical forests of Africa. These are rather strange plants which have clever traps to catch insects and other small creatures who are unwary enough to venture close to them.

The Nepenthe is a climbing plant which produces flowers in bunches. The plant’s insect-traps are located at the tip of the leaves. These traps are an extension of the main vein of the leaf and look like stems with a small bladder on the end. This bladder is known as the ascidium and insects are attracted by its colour and its sugary contents. The insects go inside the ascidium but they cannot get out again because of hundreds of little stiff, downward-pointing hairs. Below these is a highly polished area, without hairs, which is like a greased slide. The more the insect struggles, the farther down it slips until it drowns in an evil-smelling liquid.

 

Picture Credit : Google

Early in the summers pretty little bunches of golden yellow flowers about a centimeter across appear floating on the water of ponds and ditches. This is the bladderwort, or Utricularia, a planet that keeps most of its body under water and looks very innocent. However underneath its leaves the Utricularia has lots of little bladders which turn into deadly traps should any unwary insect go too near them.

These bladders have a small opening surrounded by short hairs. When an insect explores the opening the plant swallows the insect and closes the opening with a special little lid. The plant then digests the captured animal through millions of microscopic tubes in its tissue.

This plant grows all over the world, on land as well as on the water, but the bulk of the species are found in tropical regions and only about four occur in Europe.

 

Picture Credit : Google