Plant Biology: Tissues and Diseases

It is made up of more than one layer of cells and has a limited role in secretion and absorption. Their main function is to provide protection against stress. They cover dry surface of skin, moist surface of buccal cavity, pharynx and inner lining of salivary glands.

These are made up of parenchymatous cells. They are thin walled and are living.

Soil air is the space between the soil particles where it is not filled with soil water. 

These are special sclerenchymatous cells found in the cortex, pith, phloem, hard seeds, nuts and stony fruit. The flesh of the pear and guava are sometimes gritty due to the presence of sclereids. These cells are very thick walled, hard and strongly lignified. They are isodiametric, polyhedral, slightly elongated or irregular in shape. Their function is to give firmness and hardness to the part concerned.

The cell walls are thin and made of cellulose.

Fibres and fibroblasts are packed compactly in dense connective tissue. Tendons are dense regular tissues that attach skeletal muscle to bones and ligaments attach bone to another bone. Collagen is the dense irregular connective tissue present in the skin.

A vast number of fungi can cause spots on the leaves of plants. Most of them are of little consequence. A typical spot has a definite edge and often has a darker border. When lots of spots are present, they can grow together and become a blight or a blotch.

Rots are diseases that decay roots, stems, wood, flowers and fruit. Rots can be soft and squishy or hard and dry. They are caused by various bacteria and fungi. Many are very active in stored fruits, roots, bulbs or tubers.

Crown gall is a serious bacterial disease that infects and kills grapes, roses, fruit trees, brambles, shade trees, flowers, and vegetables. Galls are rounded with rough surfaces and are made up of corky tissue.

This bacterial disease affects apples, pears, fruit trees, roses, and small fruits. Infected shoots wilt and look blackened.

Fusarium oxysporum is a fungal plant pathogen that causes Panama disease of bananas.

Fusarium graminearum is a plant pathogen which causes fusarium head blight, a devastating disease on wheat and barley.

Puccinia asparagi is the causative agent of asparagus rust. It is an autoecious fungus, meaning that all stages of its life cycle – pyciniospores, aeciospores and teliospores develop upon the same host plant.

 It causes Verticillium Wilt or Maple Wilt. It attacks over 300 different cultivated plants and can persist as a saprotrophic soil organism for more than 15 years.

Pine trees are susceptible to pine pitch canker. Pine pitch canker first kills the tips of branches, then spreads down the entire length of branches, and ultimately it can kill the whole tree. Infected trees die because the fungus thrives inside the tree's vascular tissue and blocks its water supply. The fungus is spread through beetles that attack pine cones.