Plant Bio

Waxy Cuticle (Leaves)

Waxy Cuticle (Leaves)

Covers epidermis cells, reduce water evaporation

Epidermis (Leaves)

Protects mesophyll cells, transparent = light reaches mesophyll better

Spongy mesophyll (Leaves)

Irregular shape = +SA for gas exchange, photosynthesis site

Air spaces (Leaves)

Air around mesophyll = diffusion gases in atmosphere & cells +

Stomata (Leaves)

Where gases enter & exit, mostly lower epidermis, open & close w/guard cells

Veins (Leaves)

Support leaf, xylem & phloem tissue

Xylem

Transport water & minerals from roots

Phloem

Transport nutrients throughout plant

Stomata open

Guard cells swollen, cardon dioxide in, oxygen out

Photosynthesis requires

Carbon dioxide & concentration gradient btw outside & mesophyll

Gas exchange in stomata causes

Water vapor to escape plants

Stomatal density

# stomata per leaf

Transpiration

Movement water in plant & evaporation; consequence of gas exchange (water in mesophyll cells evaporates & diffuses through open stomata)

What happens during the day w/most plants

Hydrogen & oxygen out of stomata, carbon dioxide in

Transpiration process

Water in roots→xylem w/transpiration pulls (hydrogen bonds in xylem = movement up & cohesive); passive

High concentration of water in air spaces

Low concentration in atmosphere

High temperature

+Water movement speed, +evaporation rate in stomata; cold = shallow concentration gradient

Light intensity high

+Photosynthesis, +glucose in guard cells = hypertonic = +water = +turgid guard cells = open = +transpiration

Water vapour high

Worse gradient; dry = +gradient = +transpiration

Wind’s effect on concentration gradient

Evaporated water gone = +concentration gradient

Xerophytes

Plants that need little water (dry habitats)

CAM

Crassulacean acid metabolism; stomata open at night bc carbon dioxide at night = photosynthesis in day, -temp = -transpiration

Xylem tissue role

Transports water & dissolved materials up plant; thick cell walls = structural support for stem

What makes up xylem vessels

Dead xylem cells = hollow tubes = xylem vessels; water travels passively through xylem vessels

Xylem Adaptations

• No end cell walls (continuous water flow)

• No cell contents or plasma membrane (+flow)

• Pits

• Lignin

Pits (Xylem)

+movement & +flow btw xylem & adjacent cells

Lignin (Xylem)

+Cell wall strength resist pressure from transpiration & keep vessels open

Epidermis (Dicotyledonous stem)

Protects stem

Cortex (Dicotyledonous stem)

Structural support & stores starch in roots

Vascular bundles (Dicotyledonous stem)

Transport materials; tissue has xylem & phloem tissue

Xylem (Dicotyledonous stem)

Transport water & materials up stem

Phloem (Dicotyledonous stem)

Transport organic compounds throughout stem

Vascular bundles (Dicotyledonous root)

Xylem & phloem tissues, transports water & nutrients & food, tissues in stele = efficient distribution

Xylem (Dicotyledonous root)

Transports water & minerals from soil & provides support to root for +rigidity

Phloem tissue (Dicotyledonous root)

Organic nutrients leaves→roots & other parts

Cortex (Dicotyledonous root)

Stores food & nutrients (starch), transports water & solutes soil→vascular bundles

Epidermis (Dicotyledonous root)

Outermost layer root, protection against pathogens & no chemical damage; aids absorption of water & minerals

Root hairs

+SA & +efficiency in water absorption from soil

Concentration gradient in vs out roots

+Root cells

Root cells transport

Actively transport minerals

Roots absorption

Water→roots through plasma membrane in root hairs w/osmosis (passive); aquaporins in plasma membrane root cells = +water movement in root cells

Symplastic Pathway

Water→cytoplasm adjacent cells w/osmosis

Apoplastic Pathway

Water→cell walls w/capillary action

Root pressure

Water up xylem when -transpiration rate

When is transpiration rate low

+Humidity or absence leaves (deciduous trees in winter)

Translocation

Nutrients through stem w/phloem issue

Phloem tissue structure

Companion & sieve tubes; cytoplasm sieve tubes & companion cell linked w/plasmodesmata

Sieve tubes

Sieve element cells = long, narrow tubes; adapted to translocate materials

Sieve tube adaptations

• Reduced cytoplasm & no nucleus = movement of cell sap

• Protein pumps in plasma membrane = active transport

• Sieve plates

• Plasmodesmata

Sieve plates (Sieve tubes)

Pores allow cell sap w/nutrients flow btw cells

Plasmodesmata (sieve tubes)

Directly connects cytoplasm of companion cells & sieve tube = metabolic support

Companion cell adaptations

• Cytoplasm connected to sieve tubes w/plasmodesmata

• +Mitochondria = ATP for active transport of nutrients in phloem tissue

• Transport proteins for loading into sieve tubes

Translocation movement

Source → sink (storage)

Source→Sink

Photosynthetic tissues→cell respiration for ATP

Source→Sink Ex.

Mature green leaves→Immature leaves

Source (Phloem transport)

Glucose in photosynthesis→sucrose for transport (leaves)→companion cells (actively transported)→sieve tubes (w/plasmodesmata, phloem loading = +sugar concentration in phloem = hypertonic), water→sieve tubes (through xylem w/osmosis), water = hydrostatic pressure in phloem=sap→areas w/low pressure

Sink (phloem tissue)

Phloem unloading (active transport) = -sugar concentration = hypotonic, water phloem→xylem (osmosis), water = transpiration stream, -water = -pressure, sucrose→sink cells = converted to starch for energy storage or→glucose to fuel metabolic reactions in sink cell

Phloem contents

Sugar, amino acids, proteins, inorganic ions, plant hormones

Reproductive organs for flowering plants location

Flowers

Reproduction (flowering plants)

Sexually w/sperm in pollen fertilizing egg in ovule

Meiosis or mitosis (flowering plant reproduction)

Meiosis

Sexual production in hermaphrodites?

Yes (both)

Pollination

Transfer pollen male anther→female stigma

Fertilization

Sperm in pollen tube w/egg in ovule; produces zygote

Seed dispersal

Movement seed away from parent plant

Pollination & fertilization process

Pollen germinates after landing on stigma of carpel, pollen produces pollen tube→down carpal into ovary, sperm→ovule through pollen tube

How many sperm cells enter stigma

2; 1 fuses w/egg & forms zygote which undergoes cell division = embryo; 1 w/2 polar nuclei form triploid endosperm (provides nutrients for embryo)

Sepal (Insect-pollinated flower)

Protects flower before blooms

Petal (Insect-pollinated flower)

Colourful & scented to attract insects

Stamen (Insect-pollinated flower)

Male part; contains filament & anther

Filament (Insect-pollinated flower; stamen)

Supports anther & brings into contact w/insect

Anther (Insect-pollinated flower; stamen)

Produces pollen grains containing haploid sperm

Carpal (Insect-pollinated flower)

Female part; composed of stigma, style, & ovary

Stigma (Insect-pollinated flower; carpal)

Sticky part of carpal, traps pollen

Style (Insect-pollinated flower; carpal)

Connects stigma & ovary; pollen tube grows down it

Ovary (Insect-pollinated flower; carpal)

Contains ovules w/haploid eggs

Nectaries

Small, nectar-secreting structures at base of flower

Nectar

Food “rewards” for pollinators = mutualistic relationship; sugars (sucrose, glucose, fruitose); scented chemicals to attract pollinators & discourage predators

Sepals

Protect flower in bud to support petals in bloom; ring of flower & break open when flower blooms

Petals

Motified leaves surrounding reproductive parts of flowers; brightly colours w/hytopigments = animals attracted, scented; unusually shaped = attract pollinators; night-blooming flowers use pollinators active at night

Stamen

Male reproductive part; filament = stalk supporting anther adapted for transferring pollen; 2-lobed anther at tip w/sac-like structures produce pollen; pollen = microscopic body containing male reproductive part

Carpel (Pistil)

Female reproductive part; style = stalk supporting sigma in position adapted for receiving pollen; flattened stigma = tip where pollen is transferred, sticky; ovary = produces & contains unfertilized eggs in ovules, centre base of carpel, develops into seeds; ovules = within ovary, contains unfertilized eggs, becomes seeds w/successful pollination & fertilization

Cross-pollination

Pollen from anther→stigma of different flower; prevents self-pollination

Cross-fertilization Evolutions

• Different maturation times for pollen & style

• Separate male & female flowers on same plant

• Separate male & female plants

How can plants be pollinated

Animals, wind, bugs

Self-pollination

Pollen→stigma in same flower; male & female reproductive organs of plants in same flower = gametes of same flower fertilizing = in-breeding

Advantages of self-pollination

Preserve good genomes for stable environment

Disadvantages of self-pollination

Reduction in variation; greater chance of desirable recessive alleles together; decreasing genetic diversity

Self-incompatibility

Recognition & rejection of pollen by carpel of same flower; genetically controlled, inhibits growth of pollen tube down style; prevents in-breeding, promotes out-crossing

Seed dispersal

Movement of seed away from parent plant

Seed

Plant reproduction by allowing dispersion & germination of new plant

Cotyledon

Seed leaf

Cotyledon function in early development

Nutrient storage, stores nutrients essential for growth of embryo until it can independently perform photosynthesis; photosynthesis, cotyledons emerge above soil during germination & become first photosynthetic organs

Plant structures to aid dispersal

Air currents, passing animals (taken for food & dropped or stored), flowing water, explosive mechanism to fling seeds (w/turgor pressure or internal tensions)

Germination

Development & growth of plant embryo into seed; completed once shoot emerges from seed (food reserves mobilized; stored food available to embryo)

External conditions (germination)

• Water uptake (hydration of cytoplasm)

• ambient temperature

• oxygen (sustain aerobic cell respiration)

Internal conditions (germination)

• Overcoming dormancy

• Respiration provides ATP for growth & metabolic processes

• Production of plant growth regulators to initiate biochemical changes of germination (production of enzymes for mobilization of stored food)

Germination process

• Water→seed

• Plant hormone gibberellin synthesized

• Gibberellic acid stimulates digestive enzymes synthesis

• Amylase digests starch stored in seed→maltose

• Maltose→embryonic plant cell

• Embryonic plant cell uses oxygen & glucose for aerobic respiration

• Respiring embryo uses nutrients stored in seed to grow