Plants respond to stimuli based on cell signaling via the reception, transduction, and response phases. Second messenger molecules include cyclic GMP and calcium. Common hormones include auxins (stimulate stem elongation, phototropis, and fruit development) such as indoleacetic acid (IAA); cytokinins and gibberellins; ethylene (stimulates ripening of fruit and apoptosis); and abscisic acid (growth inhibitor). Ethylene can also trigger in response to mechanical stress like running into a rock, causing growth to slow. Tropisms turn a plant towards (positive) or away from (negative) a stimulus (light for phototropism, gravity for gravitropism, or touch for thigmotropism). Phytochromes absorb different wavelengths of light and trigger things like opening of the stomata. Photoperiodism controls things like blooming based on the length of night.
are produced in the apical meristem of plants and stimulate stem
elongation and phototropism as well as fruit development.
Indoleacetic acid (IAA), an auxin, occurs naturally in plants.
Cytokinins are produced in the
roots of plants and stimulate cell division and differentiation and
play a role in apical dominance.
Gibberellins promote the
elongation of plant stems and are responsible for the rapid growth
of a floral stalk, which is known as bolting.
Ethylene is a hormone that is a
gas. It stimulates fruit ripening, leaf abscission and promotes
apoptosis of plant cells.
Abscisic Acid (ABA) promotes
seed dormancy, preventing seeds from germinating until conditions
are favorable. ABA also stimulates the closure of stomata in leaves
when conditions are dry.
A tropism is a response in
which a plant turns toward or away from a stimulus. Types of tropism
include phototropism, gravitropism and thigmotropism.
Plant Hormones and Tropisms
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
The book and CD package include two full length practice exams that are presented with all questions answered and explained. The author also presents detailed reviews of all test topics and includes multiple-choice and free-response questions with answers at the end of each topic's chapter.
This book includes a review of the AP Biology exam format and scoring, proven strategies for answering multiple-choice questions, and hints for tackling the essay questions. The practice tests include answers and explanations and there is also proven test-taking strategies for both the multiple choice and essay parts.