Nature Diary

The grass is greener on the roof

D. Indumathi and M.V.N. Murthy, 
The Institute of Mathematical Sciences, Chennai

Grasses are herbaceous plants with narrow leaves growing from the base. There are many varieties. Examples of "true grasses" are cereals, bamboo and lawn grasses. Wild marsh plants are called sedges; the grass growing beside a lake are called rushes.

Grass is extremely important to most people's lives. It is a major food source all over the world. Rice, corn and oats come from grass plants, for example, and most livestock animals (cows, goats) feed primarily on grasses.

It is also used in construction (bamboo and thatch roofs) and is also used to make sugar, bread and plastics, among many other things!

More importantly, wherever it grows, grass plays a vital role in curbing erosion by keeping the soil intact.

Grasses are among the most versatile life forms. They became widespread several million years ago. In fact, fossilized dinosaur dung has been found containing phytoliths of a variety of grasses that include the ancestors of rice and bamboo! So grasses have seen many of the life forms on Earth.

Another fascinating thing about grasses is how well they adapt to various conditions: grass grows in lush rain forests, dry deserts, and cold mountains. In fact, they are the most widespread plant type. There are more than 9,000 known species of grass.

Grasses have a very simple structure. At the base of the grass plant, roots grow down into the earth. Grass roots are fibrous, or threadlike. They extend into the soil like fingers, collecting nutrients, soaking up water and securing the plant to the ground.

Grass stems, called culms, grow up from the base of the plant. In most grass species, the culms are hollow and rigid, except at the nodes -- joints that join stem segments together.

Most grasses grow once sunlight, water and nutrients are available. The back cover photo shows a clump of really tall grass simply growing on the roof of our Institute! An air-conditioner fixed on the roof provided enough leakage-water for moss to start growing. This tall grass has grown on the moss, using it as support, without any soil being present.

Of course, if you want to grow a fancy, manicured lawn grass, that is another story!