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Materials for lab Bring a digital camera if you have one available
Teaching Objectives Plant diversity: Applications and importance Plant form and function: Plant survival and human use Local and global examples of terrestrial plant types
Student Learning Objectives (1) View the plant diversity on campus (2) Know how to access information regarding plant identification (3) Be aware of differences between mosses, ferns, and flowering plants
INTRODUCTION Plants are the producers in a food web. Solar energy is stored in the chemical bonds of the sugars produced by plant photosynthesis, the biochemical process by which plants utilize light energy from the sun to produce sugar from carbon dioxide and water. Consumers in a food web derive their energy by breaking down these bonds during respiration, which releases the stored energy. Energy flowing within the food web therefore enters it by way of plant photosynthesis.
The importance of plants to the survival of humans and other animals cannot be over- emphasized. Our basic needs of oxygen, food, shelter, and clothing are provided, directly or indirectly, by plants. Because plants absorb carbon dioxide and release oxygen in photosynthesis, they may be a significant factor in reducing the "greenhouse effect", which is caused by human activities that increase the carbon dioxide in the atmosphere. Deforestation and the burning of fossil fuels (oil, coal, and gas) are two examples of such activities.
There are about 235,000 species of flowering plants in existence today. Approximately a third of these are native to temperate regions, and the remainder are found in the tropics. A vast number of tropical plants are in danger of extinction in the wild within the next hundred years because the human populations of most tropical countries continue to double every 20 to 25 years, and because the forests are rapidly being cleared for wood and cultivation. More than half of the world's tropical forests have already been cleared, and experts predict that most of what is left will be gone in less than 50 years. With them will vanish a quarter of all life-forms including, perhaps, a plant that could provide a cure for cancer or help end world hunger.
Plant Biology
Lab
So little is known of the plants of the tropics that many have not even been given scientific names. Preserved samples of these plants may well be all that are passed on to our descendants in the 21St^ century and beyond. The useful properties these plants possess can certainly be determined better today, when species are still in existence, than at any point in the future.
This week's lab is designed to introduce you to the incredible diversity within the plant kingdom, to note some of the purposes for which plants have been utilized by humans, and to help you appreciate the forms into which they have been modified and shaped by evolution.
We will look at examples of several types of terrestrial plants: ferns, conifers, and flowering plants. The emphasis will be on form and function, from the perspective of both plant survival and human utility.
PLANT DIVERSITY Terrestrial (land-dwelling) plants can be separated into four major groups based on their anatomy, reproduction, and life cycle. These four groups are mosses, ferns, gymnosperms, and flowering plants.
Mosses are non-flowering terrestrial plants that reproduce by spores. Mosses don't have vascular tissue (analogous to human veins) to distribute water within their bodies. Instead, they absorb water through pores located on all parts of the plant body. Since mosses lack veins, they are small in size and close to the ground where moisture is readily available.
Ferns are non-flowering plants that also reproduce by spores but that have vascular tissue to distribute nutrients and water to all portions of the plant body. Since ferns have veins, they can grow taller than mosses.
Gymnosperms are non-flowering plants that reproduce new plants with seeds. You probably remember from your previous work on seed germination that a seed contains the embryo of a young plant, in addition to nutritive tissue and a protective outer tissue called the seed coat. The largest group of gymnosperms, called conifers, produce their seeds in cones.
Flowering plants, more technically called angiosperms , are the most successful, diverse, and widespread of the land plant groups. Flowering plants range in size from tiny duckweed, a few millimeters in size, to Eucalyptus trees more than 100 meters ( ft.) in height. There are even flowering plants that have invaded the oceans where they produce flowers underwater.
Leaf
Shoot System
Root System
Roots
All roots are responsible for:
- anchoring the plant to the ground
- extracting water and minerals from the soil
In a typical root we can distinguish the following parts:
- Primary root - the thickest. It grows downwards.
- Secondary roots - arise from the primary root. They are not as thick as the primary one. They go sidewards.
- Root cap - is a kind of protection the roots end with. It is designed to drill the soil and it is able to guide the root growth by perceiving gravity.
- Root hairs - are minute filaments roots are covered with. They absorb water and nutrients from the soil.
Leaves
All leaves are responsible for:
- absorbing the sun's rays
- the majority of photosynthetic production (which can take place in any green part of a plant),
- taking in carbon dioxide and releasing oxygen and water vapor (breathing)
- removing waste products from the plant
- using osmotic pressure to draw water up from the roots
Parts of a leaf
tip the terminal point of the leaf
blade or lamina the flattened, green, expanded portion of a leaf.
margin edge of a leaf.
midrib the most prominent central vein in a leaf.
lateral veins secondary veins in a leaf.
petiole the leaf stalk (connects blade to stem).
stipules leaf-like appendages (at the base of petiole of some leaves).
