Leaf Identification
We used pages from Apologia's Botany (also in Apologia Biology) to identify the leaf mosaic, shape of leaf, venation of leaf, and leaf margin. We also examined the color, texture, and any other outstanding features of the bark.
Thankfully we had two girls, sisters, who knew a lot about leaves! They were able to identify nearly every tree or plant by the leaves that were brought to class.
This was from Apologia Biology Exp. 14.1 - Leaf Collection and Identification.
(worksheet, guide)
Vascular Plants
Plants with xylem and phloem (tubes for transporting water and minerals) are vascular plants.
Nonvascular Plants
Non vascular plants, such as moss, algae, liverworts, or hornworts, are short and do not have xylem and phloem. They grow near a water source so that they can absorb the moisture they need.
Vascular Plants and Turgor Pressure
When the vacuoles of plant cells are filled with fluid, they are rigid and cause the plant to stand upright. This is called turgor pressure. Food coloring allows us to see that water flowed up the xylem.
Cotyledons, testas, dicots, and monocots
A pinto bean can be divided into two halves. These are the cotyledons - the plant's first food. A plant cannot make its own food until it pokes out into the sun from beneath the soil. Since a pinto bean seed has two cotyledons, the bean plant is a dicotyledon, or dicot. Corn is a monocotyledon, or monocot.
Seeds have a covering called a testa that falls off as the cotyledons shrivel. On a pinto bean, the testa is brown and speckled.
In this picture, you can see it still in the jar, and the shriveled cotyledons on the stem below the true leaves.
Tropisms
A tropism is a growth or movement toward a stimulus.
Growth toward light (the stimulus) is called phototropism. Movement toward light is heliotropism. Growth of roots toward water is hydrotropism. Growth of roots downward is geotropism, or gravitropism. Growth of a plant upward (even before it sees the sun!) is negative geotropism, or negative gravitropism.
If a plant is placed on it's side, it will curve and begin to grow upward once more. Once righted, the plant will again curve back and grow upward, even in the absence of direct sunlight. This can cause a plant's stem to look somewhat crooked. =)
►More funny pics of bean experiments. =D
Transpiration
When the sun is shining, the stomata on the bottoms of leaves open to allow in carbon dioxide and release moisture (as well as oxygen). Transpiration is also what causes the water to move upwards in the xylem -- nothing "sucks" the water upwards. It is drawn upwards as water transpires out of the leaves. This is made possible because of the properties of water -- the molecules tend to "stick" together because of being polar. (last year's Physical Science)
Covering leaves with a baggie then watering the plant well and placing it in sunlight will give evidence that the leaves do release water in transpiration.
All pics made by my students except for the pic of them at the table.
sMiLeS,
