Seed Plants Chapter 27

Seeds are ‘better’ than spores Seed contains a multicellular young plant Seed contains a multicellular young plant Root, stem, and at least one leaf are already formed Root, stem, and at least one leaf are already formed Seeds contain a food supply Seeds contain a food supply After germination the plant is nourished until self- sufficient After germination the plant is nourished until self- sufficient Seeds are protected by a seed coat Seeds are protected by a seed coat Seeds live for extended periods at a reduced metabolism until conditions for germination are adequate Seeds live for extended periods at a reduced metabolism until conditions for germination are adequate Seed plants are the dominant plants in most terrestrial ecosystems Seed plants are the dominant plants in most terrestrial ecosystems

Major characteristics of seed plants Vascular tissue: xylem and phloem Vascular tissue: xylem and phloem Alternation of generations Alternation of generations Two groups based on seed structures Two groups based on seed structures Gymnosperms Gymnosperms An ovary wall does NOT surround the ovule An ovary wall does NOT surround the ovule Pine, spruce, fir, hemlock, gingko Pine, spruce, fir, hemlock, gingko Angiosperms Angiosperms Produce seeds within a flower/fruit Produce seeds within a flower/fruit Very diverse group Very diverse group

Gymnosperms Name means ‘naked seed’ Name means ‘naked seed’ Seeds are totally exposed or carried on the scales of cones Seeds are totally exposed or carried on the scales of cones The ovary wall does not surround the ovule The ovary wall does not surround the ovule Four phyla: Four phyla: Conifers Conifers Ginkgo and cycads Ginkgo and cycads Gnetopytes Gnetopytes

Conifers Largest and most familiar group Largest and most familiar group Pines, spruces, firs, hemlocks Pines, spruces, firs, hemlocks All are woody All are woody Leaves are needles and usually evergreen Leaves are needles and usually evergreen Most are monoecious Most are monoecious Separate male and female reproductive parts (cones) on the same plant Separate male and female reproductive parts (cones) on the same plant Wide range – from arctic to tropics Wide range – from arctic to tropics Used for building materials, resins, and landscaping/decorating Used for building materials, resins, and landscaping/decorating

Conifer species, clockwise from top-left: Western red cedar, Douglas fir, spruce, and lodgepole pine.

The conifer life cycle Male cone – pollen cone Male cone – pollen cone Produce pollen grains – each with 4 cells and large air sacs Produce pollen grains – each with 4 cells and large air sacs Pollen grains are spread by wind Pollen grains are spread by wind Female cone – seed cone Female cone – seed cone Larger and more noticeable Larger and more noticeable Pollination – occurs in the spring Pollination – occurs in the spring Fertilization – occurs about 15 months after pollination; seeds take another few months to mature Fertilization – occurs about 15 months after pollination; seeds take another few months to mature

Other gymnosperms Cycads: Cycads: Most ancient species are now extinct Most ancient species are now extinct Dioecious – separate male and female plants Dioecious – separate male and female plants Ginkgo: Ginkgo: Only one living species Only one living species Leaf extract has been used to increase blood flow to the brain and may aid memory Leaf extract has been used to increase blood flow to the brain and may aid memory Gnetophytes: Gnetophytes: Have more efficient water conducting cells Have more efficient water conducting cells Ephedrine – stimulates the heart and raises blood pressure Ephedrine – stimulates the heart and raises blood pressure

Clockwise from top left: Cycad, gingko, gnetophyte

Angiosperms Most successful plants today Most successful plants today Very important to humans Very important to humans Divided into two classes: Divided into two classes: Monocots – have a single seed leaf Monocots – have a single seed leaf Herbaceous Herbaceous Narrow leaves with parallel veins Narrow leaves with parallel veins Flower parts in multiples of 3 Flower parts in multiples of 3 Dicots – have two seed leaves Dicots – have two seed leaves Either herbaceous or woody Either herbaceous or woody Broad leaves with net venation Broad leaves with net venation Flower parts in multiples of 4 or 5 Flower parts in multiples of 4 or 5