Plant Form and Function

Plant Form and Function Learning Goal: How are plants structurally adapted for survival? Analyzing how plants detect and defend themselves against herbivores and environmental stresses (Ch 39) Refer to pg 210-213 in HoltzclawCh 39 in Campbell Media resources

Try This! (from last year) In double fertilization, how is the endosperm formed? • The fusing of two sperm and an egg • From the epidermis • From the fertilization of the egg • From the zygote during development • From the fusing of a sperm with two polar bodies

Try This! In double fertilization, how is the endosperm formed? • The fusing of two sperm and an egg • From the epidermis • From the fertilization of the egg • From the zygote during development • From the fusing of a sperm with two polar bodies

Analyzing how plants detect and defend themselves against herbivores and environmental stresses (Ch 39) You must know: The three steps to a signal transduction pathway The role of auxins in plants The survival benefits of phototropism and photoperiodism use changes in environment to modify plant growth and behaviour How plants respond to attacks by herbivores and pathogens

Try This! Both plants and animals respond to environmental stimuli. Which of the following statements are true and which ones are false? • The processes by which plants and animals perceive environmental changes are equally complex. • The processes by which plants and animals perceive environmental changes are often homologous. • Unlike animal hormones, plant hormones act only locally. • Both plants and animals have physiological cycles called circadian rhythms.

Try This! Both plants and animals respond to environmental stimuli. Which of the following statements are true and which ones are false? • The processes by which plants and animals perceive environmental changes are equally complex.TRUE • The processes by which plants and animals perceive environmental changes are often homologous.TRUE • Unlike animal hormones, plant hormones act only locally. FLASE • Both plants and animals have physiological cycles called circadian rhythms.TRUE

Try This! • What are the morphological differences in dark-grown plants and light-grown plants?

Try This! • What are the morphological differences in dark-grown plants and light-grown plants? • Dark- grown have • long stems • underdeveloped roots • unexpanded leaves • shoots lack chlorophyll But, WHY?

How does this potato change its growth when there is light?

How does this potato change its growth when there is light? • Via the Signal Transduction Pathway!

How does this potato change its growth when there is light? • Via the Signal Transduction Pathway! • The signal (light) is transduced to a response (greening)

Signal Transduction - Review • Reception • Transduction • Response

Signal Transduction - Review • Reception: Receptors undergo changes in shape due to an environmental stimulus • Ex) phytochrome proteins changing in response to light

Signal Transduction - Review • Transduction: Amplification of signal through a multistep pathway • Allows small signal to produce large cellular response • Uses protein kinases (phosphorylation cascade) and second messengers (Ca2+ and cAMP)

Signal Transduction - Review • Response: Two ways response is accomplished: • Transcriptional Modification: • ↑ or ↓ mRNA production (turning genes on/off) • Post-Translational Modification: • Activates existing enzyme molecules

Signal Transduction • Proteins include: • Photosynthesis enzymes • Plant growth hormones • Auxin levels lower to slow stem growth (focus on leaf growth)

So…. What was AUXIN? • A plant hormone… • Yes, plants have hormones too!

Examples of Plant Hormones • Auxins – stimulate elongation of cells within young developing shoots • Cytokinins – stimulate cell division • Gibberellins – stimulate stem elongation, pollen, fruit, seed development • Abscisic acid – promotes stomatal closure during drought stress • Ethylene (gas!) – fruit ripening, leaf abscission

Plant Hormones • Hormones: chemical messengers that coordinate the different parts of a multicellular organism • Tropism: Plant growth response toward or away from a stimulus • Phototropism • Gravitropism • How does this benefit survival?

Phototropism - Mechanism

Actions of hormones… • Photoperiodism – physiological response to a photoperiod (relative lengths of day and night) • Example: Flowering • Short day plants • Long day plants • Day-neutral plants • Circadian rhythms – physiological cycles that have a frequency of about 24 hours

Responses to Mechanical Stimuli • Mimosa Plant

Herbivore Defense Video Clip

Think: • Illustrate this statement with an example: “A plant generally responds to environmental cues by adjusting its pattern of growth and development.”

How do plants detect and defend themselves against herbivores and environmental stresses? Do you know? The three steps to a signal transduction pathway The role of auxins in plants The survival benefits of phototropism and photoperiodism use changes in environment to modify plant growth and behaviour How plants respond to attacks by herbivores andpathogens Try# 1 p. 213, #1-4 p. 215 in Holtz

Plant Form and Function