PLANT GROWTH. IB Topic 9.3 & 9.4 Urry text ref: Ch 28 & 31

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1 PLANT GROWTH IB Topic 9.3 & 9.4 Urry text ref: Ch 28 & 31

2 INDETERMINATE GROWTH = throughout life meristems like stem cells in humans Shoot tip (shoot apical meristem and young leaves) lateral Axillary bud meristem Vascular cambium Cork cambium Lateral meristems apical Root apical meristems

3 INDETERMINATE GROWTH Secondary Growth Secondary growth in stems Periderm Cork cambium Pith Cortex Primary phloem Primary xylem Secondary phloem Secondary xylem Vascular cambium

4 EARLY EXPERIMENTS A B C D E F G Canary grass coleoptiles

5 Statoliths

6 9.3.U3 PLANT HORMONES AUXINS Auxins promote: cell elongation, formation and branching of roots lethal in overdose (herbicide)

7 9.3.U3 PLANT HORMONES Hormones coordinate the different parts of an organism Responses to stimuli = tropisms gravitropism heliotropism (a) Unstimulated (b) Stimulated thigmotropism Leaflets after stimulation Pulvinus (motor organ) Side of pulvinus with flaccid cells Side of pulvinus with turgid cells Vein (c) Motor organs 0.5 µm

8 MICROPROPAGATION Using agar to clone plants Initiation: Selection & sterilizing Multiplication: cell division induced by hormones Rooting/pre-planting: roots induced by hormones Acclimatization: rooting in soil

9 PLANT REPRODUCTION From Ch 30 Review from IB Bio B

10 1. Plant classification Review from IB Bio B: What makes them Kingdom Plantae? type of cells? uni- or multicellular? outside the cell membrane? how do they get energy? 3 organs: leaves, stems, roots Are they like animals?

11 2. Plant Lifecycle Review from IB Bio B: Alternation of generations meiosis diploid haploid gametophyte = sporophyte = All plants follow this pattern in some way How are you different? fert.

12 Flower structure Stigma Style Anther Ovary Petal Filament Sepal 2008 Paul Billiet ODWS

13 Structure of Flowers Parts of a Typical Flower Stamen Anther Filament Stigma Style Carpel Ovary Ovary Petal Sepal Ovule Copyright Pearson Prentice Hall

14 Fertilisation The pollen grain germinates on the stigma Pollen grains (N) (male gametophyte) It grows a pollen tube down the style Stigma Its male nuclei travel down the pollen tube to the ovule Copyright Pearson Prentice Hall

15 Fertilisation The egg cell lies in an ovule in an ovary at the centre of the plant. Haploid cell (N) Ovule Ovary (2N) Copyright Pearson Prentice Hall

16 Fertilisation The sperm moves from the pollen tube to combine with the egg of the ovule to forma zygote (seed). Embryo sac (N) (female gametophyte) Sperm Egg cell Polar nuclei Pollen tube Copyright Pearson Prentice Hall

17 Fertilisation The sperm moves from the pollen tube to combine with the egg of the ovule to forma zygote (seed). As the seed develops around the ovary will develop into a fruit. Fruit protects the seed Endosperm (3N) Zygote (2N) Copyright Pearson Prentice Hall

18 WHEN DO PLANTS FLOWER? Some plants just use maturity as their cue There are adapted to day length, use photoperiod (length of day) Short day plants (SDP) Long day plants (LDP) How do plants see light?

19 Phytochromes as Photoreceptors Regulate many responses to light Photoreceptor : A phytochrome consists of two identical proteins joined to form one functional molecule. Each of these proteins has two domains. Chromophore Photoreceptor activity. One domain, which functions as the photoreceptor, is covalently bonded to a nonprotein pigment, or chromophore. Figure Kinase activity. The other domain has protein kinase activity. The photoreceptor domains interact with the kinase domains to link light reception to cellular responses triggered by the kinase.

20 How do plants see light? Phytochromes as Photoreceptors Phytochromes exist in two photoreversible states P r Full daylight, incl. Red light P fr Synthesis Responses: seed germination, control of flowering, etc. Far-red light Slow conversion in darkness (some plants) If days are longer than nights: Pfr > Pr If nights longer than days: Pfr < Pr Enzymatic destruction

21 HOW DO PLANTS KNOW WHEN TO? Example: Accumulation of Pfr above a certain amount triggers flowering in (LDP or SDP) Poinsettia is a SDP. How would I get it to bloom for Christmas? Needs12 hours of dark, no flashes