Unit 5: Plants

How do plants adapt to their environment?

How do plants adapt to their environment?

• photosynthesis: 6CO2 + H2O →light→ C6H12O6 + 6O2

• protection from herbivores: tough, prickly outer layer

• absorption through roots: water and nutrients

• gas exchange through stomata (small holes)

• reproduction: ensure gametes unite, germinate, and grow

What is the chemical formula for photosynthesis?

6CO2 + H2O →light→ C6H12O6 + 6O2

What are stomata?

Small pores in the outer layer for gas exchange

What are the three types of plant tissue?

• dermal: outer cell walls protecting against water loss, herbivores, injury, etc; covered in a waxy cuticle

  • epidermis and periderm

• vascular: transports water and nutrients, provides support

  • xylem (thick, dead at maturity, hollow), phloem (thin, living at maturity, sieve)

• ground: cellular growth, stores carbohydrates

  • parenchyma (thin, living at maturity)

  • collenchyma (thick, living at maturity)

  • sclerenchyma (lignin in cell walls, dead at maturity)

• meristematic: growth and specializes into different cells

What is and does dermal tissue do?

• outer cell walls protecting against water loss, herbivores, injury, etc

• covered in a waxy cuticle

  • epidermis and periderm

What does vascular tissue do?

• transports water and nutrients, provides support

  • xylem: thick, dead, unidirectional hollow (water and dissolved minerals)

  • phloem: thin, living, multidirectional, sieve (sugars from sources to sinks [high → low conc’n])

What does ground tissue do?

• cellular growth and stores carbohydrates

• parenchyma: thin, living at maturity

• collenchyma: thick, living at maturity

• sclerenchyma: lignin in cell walls, dead at maturity

What does the vascular cambium do?

meristematic region that forms new xylem and phloem cells

What does meristematic tissue do?

Constantly dividing spells that eventually specialize into specifc tissues and growth

What are the external main parts of a leaf?

• blade: flat part of leaf

• petiole: the stem/stalk attached to the blade

• veins: holds the vascular tissue together (made of xylem and phloem)

  • venation: pattern of veins in a leaf (monocot = parallel, dicot = network)

What are the internal main parts of a leaf?

• thin, flat cells in a single layer for light to enter

• mesophyll: specialized for photosynthesis

  • palisade: many long, tightly packed chloroplasts (catches sunlight for photosynthesis)

  • spongy: loose cells for gas exchange between envitinment and mesophyll (has vascular tissue)

What are leaves supposed to do - function?

• upper epidermis: the main source for photosynthesis and gas exchange through stomata (small pores in the epidermis)

  • photosynthesis: uses CO2 and releases O2

  • cellular respiration: uses O2 and releases CO2

What do stems do?

• connect vascular tissue of roots to leaves (water and other disoslved substances migration)

• support leaves and reproductive organs (more sunlgight = better pollination)

• storage of water and carbohydrates

What are the two types of stems?

• herbaceous: fleshy, no wood, yes photosynthesis, green

  • monocot: vascular bundles throughout

  • dicot: vascular bundles in a ring

• woody: hard, yes wood/bark, no photosynthesis (many layers of xylem)

What is the structure for woody stems?

• sapwood: youngest xylem layer for water and mineral transportation

  • heartwood: a bunch of old sapwood layers together

• cork: outer layer, prevents water loss

• cork cambium: meristematic tissue between cambium and cork

What is transpiration?

Evaporation of water through stomata, absorbs water through root system

How does water and minerals transport through the plant?

• active transport

• osmosis: water enters through root epidermis into xylem vessel (high → low concentration)

• becomes xylem sap (liquid water/nutrients) upon entering vascular tissue

  • build up of xylem sap leads to more concentration and root pressure (pushes xylem sap up with help of capillary action)

What is a source?

Plant cell with high concentration of sugars and solutes (leaf)

What is a sink?

Plant with low concentration of sugars

How is sugar transported throughout the plant?

• active transport: source to phloem (low → high sugar concentration)

• Translocation (long distance sap movement)

• passive transport: phloem to sink (high → low sugar concentration)