Biology Chapter 35 and 39 Notes Essay

2131 Words Apr 30th, 2011 9 Pages
Chapter 39

Plant Responses to Internal and External Signals

No groups of plants is more important to human survival than seed plants plants are key sources of food fuel wood products and medicine our reliance of plants

Products from Seed Plants

Most of our food comes from angiosperms
Six crops yield 80% of the calories consumed by humans

Cassava sweet potatoes

Other Products from Seed Plants

Secondary compounds of seed plants are used in medicines
Know table 30.1

Threats to plant Diversity

Destruction of habitat
In causing extinction of many plant speciesCHapter 35
Plant structure, Growth, and Development.

Overview no two plants are alike

To some people the fanwort is
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Functions of collenchyma
Flexible support, found especially in leaves, young stems and roots alive at maturity
C. Functions of sclerenchyma provide rigid mechanical support makes up the hard covering of seeds and nuts dead at maturity

Apical Meristems
Apical meristems elongate shoots and roots, in a process called primary growth.
Lateral meristems add thickness to woody plants, a process called secondary growth.

there are two lateral meristems: the vascular cambium a. adds layers of vascular tissue called secondary xylem ( wood) and secondary phloem 2.the cork cambium replaces the epidermis with periderm which is thicker and tougher.

The End

Chapter 39
Plant Responses to Internal and External Signals

A potato growing in darkness produces long thin and weak shoots that look unhealthy and lack elongated roots
These are morphological adaptations for growing in darkness is called etiolation.
After exposure to light, a potato undergoes changes called de-etiolation, in which shoots and roots grow normally.


Any response toward or away from a stimulus is called tropism. Phototropism Thigmotropism Gravitropism Heliotropisms

Tropisms are often caused by hormones and light.
hormones are chemical signals that coordinate or stimulate

Plant hormones

Plant hormones are produces in very low concentration, but a minute amount can greatly affect growth and development of a plant organ

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