Starter - what will be going on inside these dog’s brains and physiology? Try card sort. Why do they not run or fight immediately?

When threatened, apart from releasing adrenalin from the adrenal medulla……….the hypothalamus releases…. ACTH (Adreno-corticotropic hormone) Adrenal cortex30 corticosteroids Some help body resist stressors CRF (corticotropin releasing factor) released into pituitary gland

AIMS Give out plan for January Give back Promonitor 5 Plant Hormones recap Peer mark the exam question 6 Homework – Exam question 3, page 250 and 4 page 251.

Plant Growth Hormones Which tropism is this?

Explain why plants need to respond to their environment in terms of the need to avoid predation and abiotic stress. Pair and Share :– What sort of predators do plants need to avoid? How have they attempted to do so? Look at next slide for ideas

Chemical avoidance can include?

Growth avoidance can include? Thigmotropism Re-growing from base of plant

What about avoiding abiotic stress? To maximise photosynthesis / obtain more light / water / minerals e.t.c. To ensure germination / pollination / seed dispersal e.t.c.

So, a tropism is…… (page 220) Complete page 1 of booklet. Chemotropism Phototropism Geotropism and others wphttp:// wp So, what is a positive or negative tropic response? Give examples.

Name, including positive or negative A B C D E F

Plant hormones work in similar ways to our hormones. What are the similarities and differences? See page 220 to work these out – you can work in pairs if you like. Learn the table of plant hormones on page 221. Answer questions 1,2 and 3.

HormoneEffects AuxinsCell elongation / inhibits side shoots and leaf abscission CytokininsCell division GibberelinsStem growth and seed germination Abscisic AcidInhibits seed germination and growth / causes stomatal closure when stressed EthenePromotes fruit ripening

HormoneEffects 1. AuxinsA. Promotes fruit ripening 2. CytokininsB. Cell elongation / inhibits side shoots and leaf abscission 3. GibberelinsC. Inhibits seed germination and growth / causes stomatal closure when stressed 4. Abscisic AcidD. Stem growth and seed germination 5. EtheneE. Cell division A 5 B 1 C 4 D 3 E 2

Phototropism – what causes it? Cell elongation is one way of growing. how auxin causes cell elongation e.g. on the shaded side of a stem (page 1 and 223) Tell the story!

Abscission (dropping) of leaves – what causes it? (page 223)

Cytokinin production in the leaf decreases. The supply of nutrients dwindles and senescence begins. Leaf senescence causes auxin production in the leaf to fall. Cells in the abscision zone are more sensitive to ethene and…… Drop in auxin concentration causes an increase in ethene production. Cellulase production increases, which digests the walls of the abscision zone cells. (see page 4).

Apical shoot and root meristems In addition to cell elongation, plant growth also occurs when stem cells divide by ________. Meristems are stem cells.

Lateral bud meristem Give rise to side shoots

Lateral meristem Widens shoots or roots.

Intercalary meristem in monocots Found in monocots above nodes, and cause the internodes to grow longer.

Back to growing tip of apical shoot or root.

Apical Dominance The growing apical bud at the tip of the shoot inhibits growth of lateral buds further down the shoot.

Plant released from Apical Dominance by ……..? See question page 2

Auxins and apical dominance? Evaluating experimental evidence. Stem apical bud removal causes low auxin and side shoots grow, but – maybe oxygen may have stimulated another hormone production? Ring of auxin transporter inhibitor put under apical bud – again, low auxin and side shoots grow. However the 2 variables may have no effect on each other but be coincidently both affected by a third variable! Later it was found that some lateral buds increased their auxin conc when the apical bud was removed! ABA inhibits bud growth – high auxin may = high ABA in bud. Low auxin = low ABA and….? Cytokines stimulate bud growth – high auxin in apical bud attract cytokines to it to promote growth. What will happen when the apical bud is removed?

Gibberellins and Growth

Describe the effect of adding 4 – 20% gibberellic acid to mutant plants See page 3

What has been added to cause this pumpkin growth? See page 224 to evaluate experimental evidence.

Gibberellins and stem elongation – the evidence Just because gibberellins can artificially cause stem elongation, it does not mean it does so in nature. Experiment needs to work within natural concentrations and within areas normally reached in plant. 1. Found natural conc of GA in dwarf plants (le le) less than in tall (Le Le) plants. 2. Found Le codes for enzyme which converts GA 20 to GA 1. See page 225 Fig 4. Pea shoot enzymes blocked between ent-kaurene and GA 12, so can not make any GA substrates so was dwarf. It was grafted onto a dwarf (le le) plant and grew tall! How?! Shoot could not make G 20 but had the enzyme coded for by Le. So it could use the G 20 produced by the le le plant and make its own GA 1 to grow tall. Gibberellins stimulate both cell elongation and cell division in internodes of stems.

Questions 1 – 3 page 225

Describe how plant hormones are used commercially How are unripe bananas shipped today?

Auxins – taking cuttings / seedless fruit / herbicides. Gibberellins – extending fruit life / elongate apples (with cytokines) / elongate grape stalks so the grapes can…? Gibberellins – brewing – to switch on germination of barley seeds to produce maltose for beer production. Gibberellins – sugar production – sugar cane can be sprayed to promote elongation of internodes, so more sugar. Gibberellins – plant breeding – induces seed formation in e.g. young trees. Gibberellin inhibitor sprays can keep crop stems short to prevent lodging

Cytokines prevent yellowing of lettuce leaves and stimulate shoot and root growth in tissue culture. Ethene – speeding up fruit ripening e.g. apples / promoting fruit drop in cotton / promoting all female sex expression in cucumbers / promoting lateral growth in some plants. How does storing fruit in a low temp and high carbon dioxide prevent fruit ripening? Now check the quizzes at the back of your booklet. Question 6, 2010 paper – peer mark.

Answers to back page quizzes. Matching Pairs – A 11, B 6, C 7, D 5, E 13, F 8, G 9, H 1, I 14, J 2, K 3, L 10, M 12, N 4. What causes leaves to fall? C E B D A F

Auxins EcyKQ Phototropismshttp://uk.youtube.com/watch?v=wXxWOO EcyKQ O8A&NR=1 Time lapse movementhttp://uk.youtube.com/watch?v=wjZ1UYwr O8A&NR=1 5Ik&feature=related Good starthttp://uk.youtube.com/watch?v=zctM_TWg 5Ik&feature=related oVw&NR=1 moving plantshttp://uk.youtube.com/watch?v=IIsvRwNR oVw&NR=1