stimuli, receptors, and plant responses

tropism

plant bending in response to stimulus

phototropism

growth towards light

thigmotropsim

growth in response to touch stimulus

geotropism/gravitropism

growth in response to gravity

hydrotropism

growth towards water

3 plant tissue systems:

1) ground tissue system

2) vascular tissue system

3) dermal tissue system

ground tissue system

• specialized cells involved in photosynthesis

• carbohydrate storage (roots)

• support

• synthesis of hormones and toxins

• composed of simple tissues

vascular tissue system

• specialized cells involved in supporting the plant

• transports water and nutrients long distances (leaves to roots)

• 2 types of complex tissues: xylem and phloem

dermal tissue system

• outer layer of flat cells in the plant

• includes:

  • epidermal cells - protect plant, secrete waxy cuticle

  • cells that form trichomes

  • guard cells - surround stoma and regulate gas exchange and water loss by inflating and deflating

describe the venus fly trap mechanism:

1) Lever bends, causing Ca2+ ion channel on cell membrane to open (this is a type of mechanoreceptor)

2) Ca2+ diffuses into cell causing more Ca2+ to be released from ER → depolarization

3) Glutamate is released into apoplast

4) Glutamate binds to glutamate receptor to open ion channel

5) Electrical signal propagates

what is plant ECM composed of?

• fibers: cellulose, hemicellulose, lignan (cellulose fibers are linked in plant cell wall!)

• ground substance: pectin (polysaccharide or giant sugar molecule)

how do adjacent plant cells communicate?

plasmodesmata

what are other functions of plasmodesmata?

• water transport in roots

• diffusion of hormones

list three specialized receptors of plants:

• thermoreceptors

• nociceptors

• photoreceptors