Any vascular plant in which flower parts mature after fertilization into seed-bearing fruits in considered an angiosperm, or flowering plant. Flowering plants first appeared about 145 million years ago and today represent more than 80 percent of all green plants. Directly or indirectly, they represent the major source of food for all the animal species on Earth, from insects to humans.
Flowering plants also supply the raw materials for clothing such as cotton and linen, a large number of drugs and remedies, and important building materials. The flowering plants in our gardens and homes also add priceless aesthetic pleasure to our lives.
Angiosperms come in two basic forms; woody and herbaceous. Trees and shrubs represent the woody forms; herbaceous plants, which in clued many more species than we normally think of as herbs, are categorized as annuals, biennials, and perennials. Annuals complete their whole growth cycle in one season. Biennials use the first year to grow from seed and the second to develop flowers and fruits for the next generation. Perennials grow for many years and often produce flowering every year. While they may die back in winter, perennials produce new shoots each growing season from underground structures such as bulbs, rhizomes, corms, and tubers.
Pollination- the transfer of male reproductive cells to the female reproductive parts of a plants of the same species- occurs by a number of methods, some random and some more orchestrated. Some flowers require pollinators-mostly insects, but also birds, reptiles and mammals- that of the same species. These flowers often entice with strong scent and even pollinator’s reward is the nutritious pollen itself or nectar, a sweet liquid produced in the flowers.
WHAT IS PHOTOTROPISM?
Many plants, and some other organisms such as fungi, exhibit a tendency to grow toward a light source known as phototropism; this movement is very pronounced in some species. Plant’ responses also vary according to the wavelength of the light to which they are exposed, with red light often evoking the strongest response.
Plant hormones called auxins trigger cellular changes and swelling inside the plant, causing it to move toward the light.
The shoots of some vines may purposefully grow away from the light. They seek instead dark solid objects to climb; this process in called negative phototropism, or skototropism-growing towards darkness. Plant roots also exhibit this negative motion, but they also respond strongly to gravity.
Some plants move in response to the daily motion of the sun. this action, called heliotropism, does not involve plant growth and is therefore not considered a form of phototropism.