Plants A survey of Kingdom Plantae

Characteristics of Plants n All Plants are Producers - Photosynthetic n Plants are Multicellular n Plant cells have cell walls n Plants are Non Motile

Plant Evolution n Plants are thought to have evolved from Green Algae. n Modern Plants and Green Algae have the same type of chlorophyll, similar cell wall composition and both have starch as their food storing polysaccharide.

Green Algae

n Green Algae may be unicellular or multicellular and primarily live in aquatic environments n Modern Plants however are adapted to life on land

Advantages of Life in Aquatic Environment l Constant source of water - no risk of desiccation l Nutrients are readily available l Water provides support l Water is a medium for the transport of gametes l They have a moist surface for gas exchange

Life on Land n In order to survive on land plants must posses strategies or adaptations that compensate for the aforementioned advantages of life in water

Plant Classification

Bryophytes n A common example of bryophytes are mosses

Bryophyte Characteristics n Have NO true roots, stems or leaves n Gas exchange occurs through small openings called stomates n Have NO Vascular tissue

n Must live in moist areas n Usually Small in size - 2cm. n Are anchored to the ground by structures called Rhizoids n Gametophyte generation is dominant n Each Gametophyte is a separate sex

Why are Bryophytes limited to Moist environments ¶ Sperm have to swim to egg · Only posses a thin cuticle so they are prone to desiccation.

Why Bryophytes are Limited in Size. ¶ With no vascular tissue there is no support for large sizes. · Also due to no vascular tissue materials are transported via diffusion…..this can only occur over a small area.

Reproduction In Bryophytes n Bryophytes undergo what is called an Alternation of Generations Ô An alternation between a haploid gametopyte generation and a diploid sporophyte generation.

Alternation of Generations in Bryophytes n See diagram on page 476

Tracheophytes n Tracheophytes are characterized by the presence of vascular tissue n Have “True” Roots Stems and leaves n There are two groups of tracheophytes:

What is Vascular Tissue? n Vascular tissue are parts of plants that are responsible for the transport of materials throughout the plant. n 2 types of Vascular Tissue ¶ Xylem - transports water and minerals · Phloem - transports “food”

Spore Producing Tracheophytes n An example of spore producing tracheophytes are Ferns

Characteristics of Spore Producing Tracheophytes n Vascular tissue n true roots,stems, and leaves n Thicker cuticle then Bryophytes n No seeds but spores

n Sporophyte generation is dominant, Gametophyte generation is reduced n Gametophyte generation still dependent on water for reproduction n Both sex organs on one gametophyte

Alternation of Generations in Spore Producing Tracheophytes n See page 477

Seed Producing Tracheophytes

Gymnosperms and Angiosperms n These two groups of plants produce seeds. n Both have no need for water for reproduction and have true leaves, stems and roots. (needles are leaves). n In both the sporophyte is dominant (the plant is the sporophyte). The gametophytes are microscopic.

Gymnosperms n Conifers are gymnosperms. There seeds are in the female cones while pollen comes from the male cones. n They have advanced plant features (roots, leaves, stems) and usually restricted to harsh environments (cold). Why? n Thrive in cool climates, with poor soil, often found in moist seashore areas. n Some gymnosperms have leaves.

Life Cycle n They have a simple life cycle (page 479) and are often pollinated by wind. n Male gametophyte is the pollen grain n Female gametophyte is the Ovule n These gametophytes are contained within cones.

Life Cycle n Male cones release millions of pollen grains. n If a pollen grain lands on the ovule of a female cone a pollen tube will form n sperm will travel down the tube and fertilize the egg.

Life Cycle n A covering forms around the zygote and the food supply to form a seed. n When seed ripen the cones will open n seeds have papery wings and are dispersed by the wind.

Angiosperms n These are the most advanced plants and have adapted to a wide variety of habitats (everywhere you see flowers, you see angiosperms).

Angiosperms n These are the flowering plants: the reproductive structures of plants are located within the flower. n Male and female sex organs are in close proximity and are often placed to take advantage of wind or insects. n Pollen moves from one place to another to ensure fertilization of eggs. (see life cycle on page 480).

Types of Flowers Perfect Flowers n Flowers that have both male and female parts Imperfect Flowers n Flowers that have either male or female parts

Fertilization of a Flower n When a pollen grain lands on a stigma a pollen tube forms n The pollen tube grows down through the style n The tube nucleus directs the growth of the pollen tube n The sperm nuclei enter the ovule

Fertilization of a Flower n One sperm nucleus fuses with the egg to form a zygote n The other fuses with the two polar nuclei to form a cell that becomes the endosperm (Food Source) n This is know as double fertilization

Seed Structure After fertilization the ovule develops into a seed.

Fruit n After fertilization the ovary of the flower enlarges forming the fruit. The seed is contained in the fruit n As the fruit ripens the flower parts fall away.

Reasons for the success of Angiosperms n 1. Pollination is relatively easy (by wind, insects or self pollination) n 2. Flowers tend to attract insects (for pollen or nectar n 3. Seeds are protected by a seed coat (allowing seeds to pass undigested through most digestive tracts, then they grow in the free fertilizer)

Reasons for the success of Angiosperms n 4. Fruits are attractive to animals who in turn help disperse seeds (above). n 5. Seeds are able to suffer severe conditions such as fire, freezing, drought and then emerge when conditions are again suitable. n 6. Plants themselves have adapted to a wide variety of habitats.

Types of Angiosperms

Monocots vs Dicots n Vascular tissue n Parallel veins in leaves vs Netted Veins in leaves n Seeds n One Cotyledon vs Two Cotyledons n Flowers n petals in multiples of 3 vs petals in multiples of 4 or 5

Monocots vs Dicots

Special Structures