Plant responses Flashcards

Question

how do hormones travel around plant?

Answer 1

- diffusion - active transport - mass flow by diffusion in the phloem sap or in xylem vessels

Answer 2

inhibition of the **lateral bud growth** further down the shoot by chemicals produced by the **apical bud** at the tip of a plant shoot.

Answer 3

- when **shoot tip (apex) is removed**, auxin levels in shoot drop and lateral buds grow. - when **apex removed and paste containing auxin** applied to the cut end, buds didn't grow - upon cutting, a hormone could have been produced at cut end due to exposure to oxygen that promotes growth. - Due to this, **auxin transport inhibitors** applied below apex and buds still grew. - Based on results - high auxin levels inhibit lateral bud growth whereas low levels promote it.

Answer 4

- abscisic acid (**high levels of auxin maintain its levels high**) - cytokinins (**high auxin levels make shoot apex a sink for cytokinins, when apex is cut, it spreads evenly around plant**)

Answer 5

1) If you graft a plant with a dominant **Le gene** onto the homozygous le plant, the plant grows tall. 2) tall pea plants had higher conc of gibberellin 3) adding gibberellins to short plants made them grow tall 4) **Le codes for an enzyme involved in synthesising gibberellins (converts GA20 to GA1)** 5) Scientists found that short plants were homozygous for recessive allele and big plants were homozygous for a dominant allele (Le). 6) Scientists compared gibberellin conc in dwarf pea plants and tall pea plants.

Answer 6

enables production of **amylase** by activating genes that code for it, amylase can break down starch to glucose which provides a substrate for **RESPIRATION**, causing growth.

Answer 7

directional growth response to gravity

Answer 8

directional growth in response to light

Answer 9

- If a plant is laid on its side, auxin gathers in the lower half of the stem and root. - Auxin slows growth in the root, so the root curves downwards. - roots are **negatively phototrophic**. - Auxin stimulates growth (cell elongation) in the shaded side of shoot, so the stem curves upwards - shoots are **positively phototropic**

Answer 10

- direstional growth in response to water. - roots tips growing towards damper areas, increasing their access to water.

Answer 11

when seed **absorbs** water, **embryo** releases gibberellins **into the aleurone layer in the endosperm region of the seed**

Answer 12

- control plant is spun very slowly by **klinostat** so gravity is applied equally to all sides of the plant. Roots and shoots grow horizontally. - other plants are on klinostat (switched off) so shoots grow upwards and roots grow downwards.

Answer 13

- promotes active transport of H+ into cell wall. - low pH provides optimum conditions for **expansins** to work which break bonds within cellulose (H+ also disrupts these bonds). - cell wall becomes less rigid and can expand as cell takes in water

Answer 14

- stimulates enzymes that break down cell walls making fruit soft and ripe.

Answer 15

- used as **herbicides**, makes plants grow too fast so they can't get enough water or nutrients so they die - used a **rooting hormone**, lots of the same plant can be grown quickly and cheaply from one plant via cuttings.

Answer 16

- that water and/or solutes are need to be able to move backwards from the shoot tip for phototropism to happen - when a permeable gelatin block inserted behind shoot tip, the shoot still showed +ve phototropism - when an impermeable mica block was inserted, there was no phototropic response. - tests: - tip separated by gelatin block - tip separated by mica (impermeable)

Answer 17

- confirmed that the shoot tip was responsible for phototropic responses - tests: control tip removed tip covered by opaque cap tip covered by transparent cap base covered by opaque shield

Plant responses Flashcards

(42 cards)