Diversity and Adaptations of Plants

Plants became established on land  Probably evolved from multi-cellular aquatic green algae (a protist)  Plants had to do three things to survive on land –Absorb nutrients from surroundings –Prevent water loss –Reproduce without water in the environment

Absorbing nutrients  Aquatic algae and aquatic plants take nutrients directly from water (diffusion and osmosis)  Early plants and fungi developed symbiotic relationships to help plants get nutrients from rocks and soil. –Ex. Mycorrhizae  mycos = fungi  rhiza = root

Preventing water loss  Developed a cuticle –a waxy layer water proof coating on stems and leaves.  This barrier prevents water in a plant’s tissues from evaporating into the atmosphere.

Reproducing on land  Sperm of algae can swim through water b/c lives in an aquatic environment  Most land plant sperm must move without water  Sperm is enclosed in structures to keep them from drying out. –These structures are called pollen –Pollen can be carried by wind or animals

Other Adaptations  Vascular Tissues - elongated tube-like cells –Leaf – broad flat structure that traps light energy for photosynthesis –Stem – provides:  Structural support  Transports food, water, and other materials –Roots - structures that  Acquire water and nutrients from soil  Transport water and nutrients to stem  Anchor plant to ground  Some roots also store starch

More Adaptations  Reproductive Structures –Seed – contains an embryo, food supply, and a protective coat  Protects the zygote or embryo from desiccation (drying out)  Aids in dispersal –Flower – reproductive structure that produces pollen and seed  Makes plant reproduction more efficient  Can be male, female, or hermaphroditic

Plant Life cycles  Alternation of Generations –All plants have two life-cycle generations  Gametophyte (n) – produces the gametes(n) by mitosis  Sporophyte (2n) – produces spores(n) by meiosis –The gametes fuse to form a diploid zygote which develops into a new sporophyte; thus the sporophyte and gametophyte alternate.zygote

Life Cycle of Mosses Mosses reproduce sexually by forming spores. A single moss "plant" is a gametophyte (n). Sperm (n) from one gametophyte fertilizes the egg of another, producing a zygote (2n). A stalk-like structure, called a Sporophyte (2n), with a capsule at the top containing the spores (n) grows from the zygote.

Survey of the Plant Kingdom: Non-Vascular Plants  Nonvascular plants – do not have a vascular system –Simple and small in size  Water and other materials transported by osmosis and diffusion –Larger gametophyte  Rhizoids anchor the gametophyte to ground –Require water for sexual reproduction –Examples: mosses, liverworts, hornworts

Polytrichum commune Lunularia cruciata Anthoceros

Seedless Vascular Plants  Have a vascular system –Grow larger than non-vascular plants  Larger sporophyte, while smaller gametophyte develops on or below surface of soil  Still need water to reproduce  Drought resistant spores  Examples: –Ferns, Club Mosses, Horsetails, and Wisk Ferns

Club Moss Fern w/ Fiddle Heads Horsetail: Equisetum hymale Wisk Fern

Seed Plants: Gymnosperms (Naked Seed)  Seed plants whose seed does not develop within a fruit (sealed container)  Greatly reduced male (pollen) and female gametophyes. Develop within male and female cones.  Wind pollination  Examples: –Conifers, Cycads, Ginkos, Gnetophytes

Encephalartos lehmannii Ginko biloba Conifer

Seed Plant: Angiosperms (Flowering)  Have flowers where the male and female gametophyte develops.  Produce seeds enclosed in a specialized structure called a fruit –Fruits provide some protection but mostly aid in seed dispersal  Seeds have an endosperm (a stored food supply)  Two Types: –Monocots –Dicots

Monocots  Produce seeds with one seed leaf (cotyledon)  Flower parts are in multiples of 3  Long narrow leaves with parallel veins  Vascular bundles scattered  Examples: Tulips, Irises, Wheat, Corn, Rice

Dicots  Seeds with two seed leaves (cotyledons)  Flower parts in multiples of two’s, fours, fives  Leaves with branching or netted veins  Vascular bundles form a ring  Examples: daisies, sunflowers, lettuce, roses, apples, potatoes