Chapter 22: Plants

What is a Plant?• Plant mostly multicellular

organisms of eukaryotic cells with think cell walls and that mostly get energy through photosynthesis

• Autotrophs produce their own energy (chlorophyll a and b in chloroplasts)

• Heterotrophs plants gain energy from decomposing organic material

What do Plants need to survive?• Reactants of photosynthesis:

– Sunlight, CO2, Water

• Gas Exchange:– Take in CO2 but also release O2

(byproduct that can limit photosynthesis)

• Minerals/Nutrients:– Absorbed from the soil through the

roots• Space:

– Crowding limits sunlight which lowers photosynthesis rate

– Photosynthesis is a very inefficient reaction, so a high rate is needed to survive

The Plant Kingdom• 5 Groups based on

Adaptations:1) Green Algae simplest

plants; seedless2) Bryophytes complex plants

but lack main plant structures; seedless

3) Seedless Vascular Plants typical plants but seedless

4) Cone-Bearing typical plants that produce seeds

5) Flowering seed producing plants with flower adaptations

The Plant Life Cycle• All plant groups follow

alternation of generation life cycles

• Diploid (2N) Phase:– Sporophyte multicellular

phase that produces spores– Spores grow into

gametophytes• Haploid (N) Phase:

– Gametophyte multicellular phase that produces gametes (sperm and eggs)

– Gametes fuse (fertilization) to make sporophyte

Green Algae• Can be unicellular or

multicellular (volvox)• Haploid cells most of the time

and reproduce by mitosis• Haploid gametes can fuse to

make diploid zygote that can be dormant for long periods of time– Survive unfavorable

environment• Must live in water or on moist

land; nutrient rich soil

Bryophytes• Multicellular plants but lack

leaves, stems, and roots– Lack of vascular tubes

means moss can only be 1 meter high

• Most common type is moss• Rhizoids simple root-like

tubes that help absorb water and nutrients

• Most of its life is the gametophyte form and requires water to mix gametes– Must live on moist ground

Seedless Vascular Plants • Club Moss, Horsetails, and

Ferns• Vascular tissue hollow tubs

inside the plant that allow the movement of water and nutrients– Xylem moves water– Phloem nutrients

• Rhizomes underground root system

• Sporophyte releases spores which grow into heart-shaped gametophytes; sperm and eggs need water to mix

Cone-Bearing Plants• Seed plant embryo,

energy supply, and protective coating (seed coat)– Allows spreading of plants

away from water sources• Gymnosperms “naked

seed”; sporophyte release pollen grains (male-gametophyte) from Pollen Cones – travel by wind to fertilize

ovules (eggs) in Seed Cones (pollination)

Flowering Plants• Must abundant plant forms• Angiosperms “enclosed seed”; flower

contains ovaries and pollen (sperm)– After fertilization ovaries develop into

fruit (contain seeds); animals eat fruit and spread seeds in droppings

• Flowers allow pollination by animals; much more efficient than wind

• Categorize plants by:– Soft or hard stems (wood)– Annual or biennial life cycles– # of cotyledons (seed leaves); monocots

(one) or dicots (two)– Flower petals in multiples of 3, 4, or 5– Vascular buddle formations– Types of leaves

Type of Flowering Plants• 5 Classifications:1) Amborella oldest known

angiosperms; only 1 species still exists

2) Water Lily large, showy flowers3) Magnoliids wide range of

flowers in both size and complexity

4) Monocots 20% of flowering plant species; includes rice, corn, wheat, orchids, lilies, and irises

5) Eudicots 75% of flowering plant species; very diverse class