Why are there different shapes and stuctures of leaves?

Question

Why are there different shapes and stuctures of leaves?

Answer 1

To adapt to the specific needs of the climate wind / rain / sunlight, and to protect itself from wildlife in the area with things like thorns (Thorns are cactus leaves)

Answer 2

Leaf shape, color, and surface texture all play a part in transpiration rate, and defense against damage.

Leaf surface area is a factor. Large leaves have a larger boundary layer. This is a quieter layer of air as it touches the leaf. The presence of hairs or texture to hold a deeper boundary layer of air slows transpiration further. Surface texture can be use to shelter stomata in low spots. hair has the dual function of slowing the air movement and offering mechanical defense against insects chewing the leaf.

Water plants have their stomata on the upper surface of leaves to expose them to air while some terrestrial plants have their stomata on the leaf undersides to keep them shaded and cooler to slow water loss.

White to grey leaves may have dense hair covers or thicker coats of wax to prevent water loss in very arid settings. Or like the common mullein plant it has hairs with microscopic branched tips to stop grasshoppers and other chewing insects.

Temperate trees mostly have serrate or toothed leaf margins while tropical leaves are smooth edged. Climate and leaf margin are closely tied and the teeth seem to offer unfolding leaves earlier photosynthesis as trees open their leaf buds.

Ecological Significance of Toothed Leaves in Temperature Forest Trees

http://findarticles.com/p/articles/mi_m2...

Highly pigmented leaves are sometimes signaling the presence of toxins to prevent insects from even trying a nibble. In other cases the first leaves are red to protect them from UV damage while they are very tender and young.

http://72.14.253.104/search?q=cache:36WZ...

http://www.dec.ny.gov/docs/lands_forests...

Then there is leaf movement. Legumes close their leaves at night in nictinastic rhythyms. Mimosas close their leaves at a touch in thigmonastic movement.

http://en.wikipedia.org/wiki/Thigmonasty

Answer 3

It depends on the type of plant...dicot plants have leaves with characteristics like webbed veins, while monocot leaves have parallel veins (think corn leaves). Whether a plant is a dicot or monocot also affects the seed structure, number of petals, the root structures.

The different colors depend on the pigments present....green leaves contain a lot of chlorophyl, which is used for photosynthesis (converting carbon dioxide to oxygen and food for the plant), while orange and red leaves contain carteniods, which absorb light (like cholorphyls) but don't actually convert the carbon dioxide, they absorb light at different wavelengths and pass it on to the chlorophyls.

There are also a lot of different structures because plants had to adapt themselves to life on land. Land plants developed a waxy cuticle on leaves and stems to prevent water loss through evaporation, rigid stems to be closer to sunlight..