Introduction to Plants Plant structures, Signaling defences, Responses to the Environment

Why are plants important?  Food  Photosynthesis produces oxygen  Roots prevent soil erosion  Leaves absorb pollutants  Take in Carbon Dioxide

Types of Plants  Bryophytes – lack a true vascular system (xylem and phloem) –Mosses  Remain small  Need water to reproduce – sperm swims to female plant to fertilize egg – grows into stalk with spore case on end

Seedless Vascular Plants  Ferns –Have xylem and phloem –Reproduce by spores instead of seeds

Seed Plants - Gymnosperms  Nonflowering seed plants –Many produce seeds in cones - conifers –“naked seeds” – have no flesh around it.

Seed Plants - Angiosperms  Flowering seed plants –Produce flowers containing male and/or female reproductive structures

Seed  Produced from union of egg and sperm –Egg is in flower – usually deep inside –Sperm is in pollen – carried to egg during pollination –Fertilization produces embryonic plant within stored food and a protective coating

Pollination  Wind  Water  Animals – bats, insects, birds, mammals, snails, etc.

Fruits  Attracts animals so seeds get dispersed  Seeds usually can pass through animal’s digestive system to be dropped a distance away from parent plant

Structures of Angiosperms  Roots –Grow toward water –Absorb water and minerals –Transport them to stem –Store food –Anchor plant

Types of Roots  Taproot system  Fibrous root system

Root Tip  Remember the root tip we squashed to see the cells undergoing Mitosis? Root cap Zone of cell division Zone of elongation Zone of differentiation

Leaves  You already know the structure of the leaf:

Flower Structure Carpel

Fertilization

Vegetative Reproduction  Cuttings - houseplants  Runners - strawberries  Mutations – naval oranges  Grafts  Suckers – aspen roots

Plant Hormones  Chemical messengers – made in one part of plant and work on another (just like human hormones).  Auxins – responsible for growth at the end of stems – cut them off, and plant will send out shoots from the sides of stems. Pruning uses this info to make bushier plants.  Others include cytokinins for root growth, Giberellins for seed growth, ethylene for fruit ripening, and abscisic acid for fruit and leaf growth.

Plant Responses  Phototropism  gravitropism  Thigmotropism  hydrotropism

Dormancy in Winter  Deciduous Trees –Lose leaves in autumn – Why? –Low level of metabolism in winte –Growth is suspended until leaves grow in spring

Evergreen trees  Metabolism slows in cold weather, but they can start up any time the temperature rises.  Lose leaves all year long, a little at a time.

Photoperiodism  Plant responds to intervals of day and night  Long night plants – flower in late summer or early fall  Short night plants – flower in early to midsummer

How long do plants live?

Monocots vs Dicots

How a Plant Grows:

Secondary Growth:

Tree trunks:

Water Transport

Fruits: Mature ovary

Growth of Seed: