Plant Unit Review

Plant Maintenance Unit

General characteristics of plants – multicellular, eukaryotes, cell wall made of cellulose, autotrophs/ producers

What they need to survive – sunlight, water and minerals, gas exchange, movement of water and nutrients

Leaves  

• Structure – cuticle, upper epidermis, palisade layer, spongy layer, vein (xylem and phloem), lower epidermis, guard cells, stomates, chloroplasts

• Function – photosynthesis (leaf is adapted for this), transpiration, gas exchange (diffusion)

• Opening and closing of stomates/guard cells – example of feedback mechanism, has to do with photosynthesis, ATP/active transport, K+ ions, osmosis of water, guard cells swell, stomates open 

Stems

·      Structure – lenticels, xylem, phloem

• Function – transport, support, gas exchange, food storage
• Types – herbaceous, woody stems (cork, cortex, phloem, vascular cambium, xylem, pith)
• Tree rings – tree age, climatic conditions, fires, etc.

Roots

• Structure – root hairs, epidermis, cortex, endodermis, vascular bundle/conducting tissue (xylem and phloem)
• Function – water absorption, food storage, anchorage, transport, root pressure

Water transport

• Factors affecting water loss – wind, temperature, humidity, sunlight, water availability

• Root Pressure - active transport of minerals in water diffuses in by osmosis.   

• Transpiration (evaporation of water from leaf) and transpirational pull (water to water molecules = cohesion)

Chemical Control

• Auxins – plant hormones, growth regulators, produced in root tips and stems at meristems

• Tropisms – unequal plant growth in response to environmental stimulus (change)

• Phototropism – growth in response to light
• Geotropism – growth in response to gravity
• Hydrotropism – growth in response to water
• Thigmotropisms – response to touch
• Positive tropism – turning toward stimulus
• Negative tropism – turning away from stimulus