economic importance of plants

• food— 80% human calories (stored starch) from 6 crops– wheat, rice, maize – potatoes, casava, sweet potatoes

• fiber, wood (lignified cell walls)– fabric, paper, building material, fuel

economic importance of plants

• medicine (2ndary chemical compounds)– aspirin = synthetic version of

compound from willow– Table 30.1– 1/4 prescription medications--plant

produced (more efficient)

Artemisia produces antimalarial compound in glandular hairs

Science Jan 15, 2010

Plant nutrition

• autotrophs w/ chlplsts--PS pigments– chla & accessory pigments: chlb, carotenoids

• light energy from sun, C from CO2

• minerals N, P, K, Ca, Mg, S – (and 7 micronutrients)

• make sugar; store as starch• energy from breakdown of food

– mitochondria--cellular respiration (requires O2)

ecological importance of plants

• ~290,000 sp. +• diverse habitats• nutrient cycling

• base of terrestrial food chain (Fig 54.11)– primary producers

• energy transfer ~10% efficient – (Figs 55.9 & 10)– most goes to cellular respiration, waste-->

heat

carbon cycle

Fig 55.14

C from air stored in organisms, fossils, soils

respiration,decomposition, burning

return to air

CO2 and plants

w/extra CO2, plant growth increases but limited by other nutrients

growth affected by temp & precip plants may not be able to migrate fast enough, esp. w/ habitat fragmentation

Fig 55.14

water cycle

H20 evap (pl. stomata) & retention

shade

fallen leaves—>humus soil holds H20

habitat for detritivores (decomposers)

nitrogen cycle

Fig 55.14

prokaryotes convert N

plants absorb N, animals eat plants

plants retain N that would wash away

eutrophication:

increased nutrients in waterphytoplankton & plants grow abundantly

respire at night (use up O2)aerobic prok degrade (use up O2)obligate aerobes die (dead zones)

Fig 55.18

phosphorous cycle

Fig 55.14

P cycles between autotrophs (absorb it) & heterotrophs

or lost until geological processes return it

sticks to soil that is rich in organic matter

Hubbard Brook Expts: studies of nutrient cycling

• isolated valleys, bedrock, drain indply• 60% H2O leaves, 40% evap through plants• internal cycling conserves nutrients• remove plants from one valley

– 30-40% increase water loss– minerals lost: Ca2+, K+, NO3

-

– conclusion: plants control nutrient cycling• acid rain dissolves Ca2+, affects biomass

– added Ca2+ improves plant health

rates of nutrient cycling

dep. on temp, moisture, nutrients

faster at higher temps, enough H2O

slower if cold, too dry or too wet

example:

peatlands cool & wet anaerobic

organic matter accumulates

CO2 stored

sexual reproduction

• haploid: having 1 set of chromosomes

• diploid: having 2 sets of chromosomes

• polyploid: having >2 sets of chromosomes

sexual reproduction

• mitosis: division of nucleus to form

2 nuclei w/same no of chromosomes of original nucleus

• meiosis: division of nucleus to form4 nuclei w/half no. of chromosomes of original nucleus

sexual reproduction

• fertilization (syngamy): fusion of 2 gametes to form 1 zygote

• isogamy: gametes same form and size• anisogamy: gametes same form, different

size

• oogamy: large non-motile gamete (egg) & small motile gamete (sperm)

Life cycle terms

• alternation of generations: life cycle with at least 2 multicellular phases that can be distinguished by reproductive cells and sometimes by morphology

• spore: a reproductive cell capable of growing into a new organism w/out fusing with another cell

Life cycle terms

• sporophyte: multicellular spore-producing phase of organism with an alternation of generations

• gametophyte: multicellular gamete producing phase of organism with an alternation of generations

Life cycle terms

• heteromorphic (“other form”) generations look different

• isomorphic (“same form”) generations look the same

• alternation of heteromorphic or isomorphic generations

2n

nmeiosis syngamy

zygote

gametes

sporophyte

spores

gametophyte

kelps, plantsFig 28.16

3 Life Cycles Fig 13.6

n

2n

zygote

ChlamydomonasFig 28.22

n

2n

gametes

humans

mitosis mitosis

mitosis