- Common features.
- Main morphological types.
- Main organs.
- Main groups: bryophytes, pterydophytes, gymnosperms and angiosperms.
- Nutrition: photosynthesis vs. respiration; role in the carbon cycle.
- Basic interaction mechanisms.
- Reproduction in angiosperms.
Vocabulary: Types of Plants
|Bryophytes||Terrestrial plants that lack a vascular system, are dependent on environmental moisture for reproductive and nutritive functions, and that disperse spores for reproduction. The group includes mosses, liverworts and hornworts.|
|Tracheophytes||Plants with a vascular system that helps them to stay upright and transports the sap, the plants' nutritive liquid mixture. The vascular system is made up of the vascular tissues xylem and phloem. The group includes pteridophytes and flowering plants.|
|Pteridophytes||Terrestrial plants with a vascular system that are dependent on environmental moisture for reproductive and nutritive functions and that disperse spores for reproduction. The group includes ferns and horsetails.|
|Flowering plants||Or seed plants. Plants with a vascular system that are not dependent on environmental moisture for reproductive and nutritive functions and that disperse seeds produced inside flowers for reproduction. The group includes gymnosperms and angiosperms.|
|Gymnosperms||Vascular flowering plants in which the ovules are not protected by an ovary. As they don't have ovaries, they don't have fruits neither, but cones instead. Their flowers are not very conspicuous, as they lack petals and sepals. They are woody and most of them belong in the conifers (such as the pines, cedar-trees, fir-trees, spruces and cypresses).|
|Angiosperms||A vascular flowering plant in which the ovules are enclosed inside protective ovaries and the seeds inside fruits. They use to have well-visible flowers that, when complete, are made up of sepals, petals, stamens and pistils. They can be herbaceous (like the poppy) or woody (like the oak).|
|Leaf||It is the photosynthesis and transpiration organ in plants. Its two main parts are usually the petiole (a slender stem that supports the blade) and the blade (the green and usually flat area, with a midrib and secondary veins). When they have one only blade, they are called "simple leaves", whereas if they have several leaflets (each one resembling a single leaf with its petiole and its blade) they are called "compound leaves". You can tell whether something is a leaf or just a leaflet by watching the stipules: two membranes that are always at the base of the leaf, and never in the base of a leaflet. Holm-oaks have simple leaves, while ash-trees have compound leaves.|
|Palmate||Compound leaves can be palmate, resembling a hand, with the leaflets outspread.|
|Pinnate||Compound leaves can be pinnate, resembling a feather, with the leaflets arranged on both sides of a central axis.|
|Whorl||Two or more leaves or other structures surrounding a stem at the same point.|
|Bract||A leaf associated with the flowers or inflorescences of a plant. Bracts are usually different in appearance to the other leaves on the plant. The lime-tree has very conspicuous elongated, narrow and pale-green bracts.|
|Involucre||A whorl of bracts, often cup-like, at the base of a flower, an inflorescence or a fruit. Daisies have involucres at the base of their inflorescences, and oaks have involucres at the base of the acorns.|
|Deciduous||To fall off or shed seasonally; usually refers to the leaves of a plant. It's opposite to evergreen. A poplar has deciduous leaves, while a holm-oak is evergreen.|
Mind Map: Dicotomous key of leavesSource
Do it yourself: Making a Plant CollectionAdapted from The University of Arizona
What is it?
When scientists preserve a specimen of a plant (or part of a plant) they usually flatten it, dry it, and mount it on special paper. Preserved in this way the plant specimen can be stored for many years without falling apart.
Before you start
Before collecting plants in the wild, you should understand the legal issues of the ownership of the land and its resources, and the ethical issues of possible damage to wild plant populations and to endangered species. It is legal to collect plants only with the permission of the owner of the property on which they are found.
What to collect
Picking a few leaves or flowers usually does not give a representative picture of a plant. Pieces of specimen plant material need to be large enough to show the characteristics of normal growth and development. Taking a branch, stem or even the entire plant may be required to get a good specimen. If the plant is small, take the whole thing, roots and all, or even several of them. If large, get a branch about 25 cm long, with leaves, flowers, and fruits, if possible. A "sterile" specimen (one with leaves only) may be impossible to identify. Even an old empty seed capsule can be helpful if that's all you can find.
The date the plant was collected and the location as exactly as possible. Record anything that the specimen won't show, for example, the size of the plant, flower colour, whether the plant is woody or not, etc. Note what kind of a place the plant was found, e.g., in gravel at stream edge, in shade under live oaks, in a sidewalk crack…
How to press a plant
Place the specimens between newspaper sheets and write the name of the species alongside. Alternatively, you can separate the specimens with corrugated cardboard (for air circulation) and blotter paper or paper towels to absorb moisture. Arrange the plant so that all parts show (for example, don't put the flowers between layers of leaves). Place the stack between boards and strap them tightly or place a heavy weight on top (such as a pile of heavy books). Put the stack where there is good air circulation, but not too much heat: you don't want to cook them.
Examine the plants daily and change newspapers or blotters when they become too wet. Remove plants from the stack when they are dry. You can kill insects in dried plant specimens by freezing them for three or four days, and keep them pest-free in a tightly sealed plastic bag.
Once the plants are dry enough, stick each specimen in a cardboard folder. Label them writing their Latin (scientific) and English names, along with all the other data that you previously recorded (collection date and place, description of the specimen...).