Herbs-Shrubs-Trees, Biology tutorial


The level of growth and progress varies in the plant kingdom. Some of the plants in the kingdom include more advanced roots, stem and leaves than other; some finish their life cycle in one year, some in two years and several in more than two years. The vascular tissue as well differs in terms of arrangement, structure and functions. Some plants contain soft stem whereas others encompass woody stem.


These are plants which don't generate permanent shoot systems however die at the end of one growing season. They don't grow tall and their shoots are soft and greenish and encompass very little or no tough woody tissue. There is a little growth in diameter and the plants are generally short-lived. The outer surface comprises of a thin epidermis in which stomata are present. The green color of the stem is caused through the presence of chlorophyll and points out that the food manufacturing capability of such sterns. Examples of herbs comprise pepper, sunflower, beans, and tomato and so on. Herbs might be annuals or perennials. Herbaceous stems are classified into monocotyledonous and dicotyledonous.

Herbaceous Monocotyledonous Stem:

The herbaceous monocotyledon stem's vascular tissue exists as scattered bundle of xylem and phloem; however the bundles might be more numerous at the periphery of stem. Apart from for the palm trees and certain other monocots, which encompass an anomalous cambium, no cambium and therefore no secondary tissue is present; a little growth in diameter is based on growth of the cells of primary tissues. Even although no definite arrangement of vascular bundles exists - the xylem-phloem by no means form continuous cylinders of tissues.

Herbaceous Dicotyledonous Stem:

In such stems, the vascular tissue is as well arranged in discrete bundles, however the bundles themselves are arranged in a methodical ring and not scattered. The cambium, that is visible among the xylem and phloem, might be restricted to the individual bundles or might be continuous from bundle to bundle.

Whatever the arrangement, the secondary tissues are badly developed and the stem remains non woody.


These contain hard woody shoot system and grow bigger than herbs and don't die at the end of the season. Their stem forms numerous branches that grow close to the ground. The outer surfaces of the older stems are rough and covered with cork example the bark of trees and shrubs. In this rough surface are lenticels that are really openings under which the cells are loosely arranged with numerous intercellular spaces. Gaseous exchange can occur via these openings. A young woody stem might have chlorophyll and carry on photosynthesis for a short period, however as the diameter rises and the cork form, this capability is lost.

However, young stems are all herbaceous in look at first, and the woody features build up as the stems become older. The raise in diameter of such stems results mostly from the production of wood and cork. Examples: Hibiscus, Tecoma, Oleander and Pride of Barbados.


Trees grow bigger in size than shrubs and encompass a single main trunk. Trees have hard woody ms that don't die at the end of each growing season. There are many trees that shed leaves yearly and are termed adeciduous plants whereas some others retain green leaves all through the seasons (ever-green plants).  The difference among a tree and a shrub is just one of growth-form instead of any intrinsic difference. In a tree, the stem (or trunk) grows erect over the ground before branching takes place; whereas in shrubs, some stems instead equal size generally occur at or close to the ground level. Illustrations of trees comprise silk cotton, Iroko and so on.


Ephemerals are the plants having very short life cycles example: seasonal plants like grasses.

Annual Plants:

Once a seed has germinated, the growth and progress of the plant are affected by both the atmosphere and the inherited features of that specific kind of plant. Factors of the atmosphere would comprise:

  • Water supply
  • Temperature
  • Supply of minerals in the soil
  • Light
  • Oxygen and carbon-dioxide
  • Parasites or herbivores

Biennial Plants:

There are plants which pass via two dissimilar phases in their lifecycle. They encompass a longer life span of two years. The biennials grow vegetative in the first season and store food. The food is used in the second season at the flowering and fruiting phase. Recent investigation have explained that temperature affects flowering in biennial plants. Most of the biennials will flower just after exposure to relatively low temperature, the condition which exists among their two seasons of growth. Throughout the first season, growth is generally vegetative. Throughout the second season plants generate flower stalks and finally seeds.

Perennial Plants:

They might be trees, shrubs or herbs. They nurture year to year. They are either herbaceous or woody perennials. In herbaceous perennias the aerial part dies at the end of each year. Illustrations are plants along with bulbs, corm, tubers and rhizomes (e.g. ginger). Herbaceous perennials, sprout again at the starting of the next growing season. Woody perennial are mostly shrubs, trees and vines.

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