You have a reading quiz at the start of class. Good Afternoon! Please hand-in your xylem vs. phloem comparison chart in the green bin. Put up your dividers. You have a reading quiz at the start of class.

What are we doing today? Reading Quiz (Ch. 26.1-2) Video: “Growing” Lecture: Plant Growth & Development Environment & Genetics Gibberellins & Auxin Return Ch. 21 & 24 Tests Log book check-in/ Final paper draft

“Growing”

26.1 – What are key factors in plant growth & development?

26.1 – What are key factors in plant growth & development? Environmental cues Receptors Hormones Genome

26.1 – What is the evolutionary benefit of seed dormancy?

26.1 – What is the evolutionary benefit of seed dormancy? Some dormant seeds are unable to germinate even when the conditions for germination are favorable. Why?

26.1 – What is the evolutionary benefit of seed dormancy?

26.1 – How can seed dormancy be broken? (How do seeds germinate?) SEEDS very negative water potential – will take in water if seed coat is permeable

26.1 – What is the relationship between hormones and receptors? HORMONES – chemical signals that act at very low concentrations at sites distant from the source PHOTORECEPTORS – pigments associated with proteins that respond to light (environmental cue) and regulate developmental processes which are responsive to light (e.g. seed germination)

26.1 – What is the relationship between hormones, receptors and plant development? Environmental cues/ hormones  receptors  relay molecules  (encoded by genes) regulatory proteins & enzymes  response

26.2 – Gibberellins Seed germination (e.g. trigger synthesis of digestive enzymes to digest endosperm to release nutrient monomers to use in cell production) Stem growth (effect on dwarf plants) – control flower height (artificial selection) Fruit development – seeds are source of fruit growth (grape experiment – way to make big seedless grapes)

26.2 – Auxin Phototropism – response to light (higher concentration on shaded side) Diffuses in polar fashion - unidirectional (stimulating cell elongation) Gravitropism – response to gravity Root initiation (experiment to induce roots in shoots with auxin solution) Leaf abscission (autumn leaf fall – decrease in auxin through petiole) Apical dominance (apical buds inhibit growth of auxiliary buds – allows for growth of main stem - Christmas trees) Fruit development (parthenocarpy fruit formation without fertilization – seedless grapes, bananas and cucumbers) Cell elongation – auxin induced cell expansion (acid growth hypotheses)

26.2 – Plant Hormones vs. Animal Hormones ACTIONS of plant hormones are NOT unique and specific – unlike animal hormones PRODUCTION of plant hormones occur at tissues triggered by different cues (unlike in animals where usually a specific organ or site produce hormones)

Gibberellin & Auxin Venn Diagram

Reminders! DRAFTS of final paper submitted BEFORE Saturday will get feedback this weekend. PROJECT due TUESDAY (final paper, log book, photos) – TIPS on how to write a scientific paper are posted on homework blog. CH 25 & 26 TEST on THURSDAY Ms. Chan will attempt to do a review video for Chapter 25 & 26 – please check website for an update of the link.