The plant body  (Page 22/6)

Introduction

A mile and a half from town, I came to a grove of tall cocoanut trees, with clean, branchless stems reaching straight up sixty or seventy feet and topped with a spray of green foliage sheltering clusters of cocoanuts—not more picturesque than a forest of colossal ragged parasols, with bunches of magnified grapes under them, would be. I once heard a grouty northern invalid say that a cocoanut tree might be poetical, possibly it was; but it looked like a feather-duster struck by lightning. I think that describes it better than a picture—and yet, without any question, there is something fascinating about a cocoanut tree—and graceful, too.

Palm tree on a tropical beach

Twain's observations about the "cocoanut tree" focuses on some of the more obvious parts of a plant: the stem, the leaves, the seeds, etc. Some of the other parts of a plant are less obvious, but not less important to the health and well-being of the organism. Like animals, plants have organelles, cells, tissues and organs.

Plant organ systems

In plants, just as in animals, similar cells working together form a tissue. When different types of tissues work together to perform a unique function, they form an organ; organs working together form organ systems. Vascular plants have two distinct organ systems: a shoot system, and a root system. The shoot system consists of two portions: the vegetative (non-reproductive) parts of the plant, such as the leaves and the stems, and the reproductive parts of the plant, which include flowers and fruits. The shoot system generally grows above ground, where it absorbs the light needed for photosynthesis. The root system , which supports the plants and absorbs water and minerals, is usually underground. [link] shows the organ systems of a typical plant.

Plant tissues

Plants are multicellular eukaryotes with tissue systems made of various cell types that carry out specific functions. Plant tissue systems fall into one of two general types: meristematic tissue, and permanent (or non-meristematic) tissue. Cells of the meristematic tissue are found in meristems , which are plant regions of continuous cell division and growth. Meristematic tissue cells are either undifferentiated or incompletely differentiated, and they continue to divide and contribute to the growth of the plant. In contrast, permanent tissue consists of plant cells that are no longer actively dividing.

Meristematic tissues consist of three types, based on their location in the plant. Apical meristems contain meristematic tissue located at the tips of stems and roots, which enable a plant to extend in length. Lateral meristems facilitate growth in thickness or girth in a maturing plant. Intercalary meristems occur only in monocots, at the bases of leaf blades and at nodes (the areas where leaves attach to a stem). This tissue enables the monocot leaf blade to increase in length from the leaf base; for example, it allows lawn grass leaves to elongate even after repeated mowing.