The Evolution of the Plant Kingdom
Understanding the Development and the Science of Plants
Oct 16, 2008
Plant chemicals were present in the ocean about 1.5 billion years ago with the origination of algae; the first known land plants didn't appear until about 435 to 500 million years ago with the appearance of plants in wet mud, growing close to fresh water. Land plants were subject to more sunlight, minerals and carbon dioxide which resulted in a transformation to stored sugars and oxygen.
The evolution of plants progressed rapidly about 375 million years ago; plants became bigger and began to differentiate, resulting in the production of two types of spores for reproduction, male and female. Gymnosperms were the next to evolve which are today's seed-producing plants such as pine trees. Angiosperms followed, about 150 million years ago; these were flowering plants confining their seeds in an ovary (flower). Angiosperms quickly dominated the plant world but how they suddenly evolved is still hotly disputed by scientists today.
The Role of Chemicals in Plants
Scientists commonly believed up to the 1990s that plants produced chemicals only as a waste product of the plant's metabolism. Primary metabolites such as amino acids and sugars are essential to a plant's ability to function in doing such activities as collecting water; secondary metabolites, such as chemicals, were dismissed. It is now known that secondary metabolites are hugely important to a plant's existence.
Flowering plants have to be more sophisticated than their counterparts in the animal kingdom, as they do not have sensory organs. Flowering plants collect light energy through proteins in light-sensitive compounds, replacing the function of eyes in primates. A plant's roots have the ability to detect ammonium salts and nitrates in the soil, needed for a plant to grow, and will move towards them to obtain them.
A Plant's Defense System of Chemicals
Other chemicals will attract birds and animals to pollinate a plant for reproduction. To protect themselves from being eaten by animals, insects and microbes, plants have a sophisticated system of bio-active substances. Some plants can communicate with their neighboring plants to warn them of an impending danger.
If a plant senses a disease-causing virus, it will release chemicals to both protect its own leaves and to warn its neighbors. Chemicals in the air alert the neighboring plants to release their own defensive chemicals against the attacker. An aggressive caterpillar which is intent on destroying a plant, through its munching of the leaves, will alert the plant to release chemicals that are capable of attracting a wasp; the wasp will lay eggs which will kill the caterpillar on hatching.
The Importance of Understanding a Plant's Chemistry
Plants are complex and sophisticated entities which have evolved over billions of years; their uses are many. They provide food, shelter and medicine in a variety of situations. They are today used in herbal medicine and in aromatherapy, demonstrating their power to heal; native people have used plants for centuries. However, it is essential to understand a plant's chemical composition to avoid potentially harmful, and sometimes lethal, effects.
References:
Swerdlow, Joel L PH.D., 2000 Nature's Medicine: Plants That Heal Washington D.C USA:National Geographic
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