Woody And Herbaceous Stems

Introduction

The stem is a part of the plant that holds up other structures such as the leaves and flowers. This is important as the leaves need to be held up to the sun to get its light forphotosynthesis and the flowers need to be held up to be available for pollination. Stems also carry water and minerals up from the roots to the leaves to help with photosynthesis and take food back downto be stored and distributed to the plant as it has need. The tubes in the stem that take the water and minerals up into the plant are the xylem and the tubes that carry the food back down are calledthe phloem.

Stems that grow above ground are called aerial stems, and those underground are known as subterranean. Aerial stems are either woody or herbaceous. Plants with woody stems includetrees and shrubs. These plants are rigid because they contain large amounts of woody xylem tissue. Most herbaceous stems are soft and green because they contain only small amounts of xylem tissue. Anexample os herbaceous stems are cactuses.

Woody Stems

The woody stems as their name implies, are covered by bark.
A plant with true woody stems contains wood, which is primarily composed ofstructures made of cellulose and lignin. These structures provide support and a vascular system which woody plants use to move water and nutrients from the roots to the leaves and to move sugars from theleaves to the rest of the plant. Most woody plants form new layers of woody tissue each year, and so increase their stem diameter from year to year.
Probably the most obvious example of a woody stem isa tree trunk.  Trees are a special woody stem and consequently have unique parts that other woody stems do not.  For example, a tree contains heartwood, sapwood, and cork.  Even so, it is notuncommon for woody stems to start out as a bush or plant and eventually grow into a tree.
Woody stems have scars where twigs and fruit have dropped off and little openings for transpiration.
When...