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Eukarya • eukaryotic, multicellular, photosynthetic autotrophs • mostly terrestrial (ability of the few aquatic plants to live in water evolved more recently)

alternation of generations – gametophyte (haploid, “n”) generation alternates with (diploid, “2n”) generation

1 Adaptations to on land • waxy on surface to reduce water loss • specialization into root (to absorb water & nutrients) and shoot (to absorb light & CO2) • vascular tissues for more efficient transport of materials • seeds to protect embryos from drying up and other hazards, provide nutrition for developing seedling and allow for widespread dispersal • flower for more efficient process & with ovaries to protect seeds • sporophyte generation (2n) became more dominant over gametophyte generation (n)

Plant phylogeny and selected major phyla

flowering Bryophyta Pterophyta Coniferophyta Anthophyta || |______|flowers ||______|seeds |______| vascular tissues |

2 Bryophyta nonvascular, n generation prevalent, many have separate male and female n plants, sperm swims to reach egg, 2n parasitic to female n, spores on top of 2n disperse

Seedless vascular plants Phylum Pterophyta 2n more dominant and more structurally complex than n, bisexual n plant, sperm has to swim to egg, spores are produced and released from sori

3 Vascular seed plants “” Phylum Coniferophyta • n parasite of 2n, evergreen trees, with needle-like , unflagellated sperm produced by a dispersing pollen, new 2n grows from seed

Vascular seed plants “Angiosperms” Phylum Anthophyta flowering plants

• most diverse (about 250,000 spp. are known) & most widespread of all plants, n parasitic to n, two unflagellated sperm produced by a dispersing pollen fertilize egg and another in the embryo sac (double fertilization), after fertilization, ovule becomes the seed, ovary becomes the fruit, new 2n grows from seed

4 Phylum Anthophyta Eudicots Class Monocots

5 Plant structure & function (focus on angiosperms/anthophytes)

• root system - obtains water and mineral from soil; numerous tiny root hairs increase surface area; some roots are modified roots as storage organs such as those of carrots, turnips, sugar beets and yams

• shoot system - obtains light and CO2 from air to be used for food production (in vegetative shoots, i.e., stem & attached leaves) and for reproduction (in floral shoots, i.e., flowers)

6 plant cell types parenchyma thin -walled collenchyma uneven thickening of cell wall sclerenchyma thick-walled

plant tissue systems

• dermal tissue system (epidermis) - single layer of tightly packed cells that covers & protect young parts of plants • vascular tissue system - xylem and phloem for transport and support • ground tissue system – occupies space between epidermis and vascular tissue systems

7 Plant growth • grows by adding “new parts”, hence, in any plant, there are parts of different ages; regions of growth are the meristems (generalized parenchyma cells capable of dividing) • controlled by internal and external signals, allowing the whole plant to constantly adjust itself to environmental changes, e.g., via plant hormones primary growth – elongation secondary growth – increase in width of root and stem

8 plant transport • involves transport of water and minerals (xylem sap) upward from roots & transport of photosynthetic products (phloem sap) all over the plant

• some adaptations to reduce water loss: small, thick leaves, stomata concentrated on the lower surface, stomata located in depressions shielded from dry wind, leaf shedding, specialized photosynthetic pathways

9 sexual reproduction in flowering plants • meiosis in anther of flower produces male spores (become pollen grain) while meiosis in carpel produces female spores • pollen released to find compatible carpel (pollination process) • pollen divides mitotically, becomes a mature pollen tube (n), long enough to reach the spore in the ovary • female spore in the ovary divides mitotically, becomes mature embryo sac (n)

pollination syndromes

10 • as pollen tube reaches the ovary, it produces and releases 2 unflagellated sperm while the embryo sac produces 8 nuclei, one becomes the egg; 2 other nuclei (polar nuclei) retains the cytoplasm of the developing embryo sac

• 1 sperm fertilizes the egg forming a diploid (2n) zygote while the other sperm fuses with the 2 polar nuclei to a 3n cell at the center of the embryo sac (double fertilization); forms the seed (fertilized ovule)andfruit (fertilized ovary)

11 • a mature seed contains the 2n embryo that developed from the zygote and the 3n endosperm that developed from the other fertilization event • cotyledon (seed leaf) develops from the growing embryo; both endosperm & cotyledon provide “food” for developing embryo

seed dormancy (escape in time) allows seeds to stay dormant until a specific stimulus (e.g., fire, extreme wetness) induces it to germinate seed dispersal (escape in space) allows them to be carried away from where parents are growing

seed dispersal

12 asexual reproduction in flowering plants

• offspring (clones) derived from parents without DNA shuffling; may be through vegetative reproduction such as fragmentation or asexual seed production

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