Lecture 12: Gymnosperms And Angiosperms
12: Gymnosperms and Angiosperms Gymnosperm– Intro and evolution– Life cycle and reproduction– Uses and significance Angiosperms: Floweringplants––––Intro and evolutionLife cycle and reproductionUses and significanceMonocots vs. dicots
Kingdom Plantae Evolutionary tree of plants From primitive more advanced traitsBryophytesGymnospermsFlowers GreenalgaancestorVascular Terrestrial
GYMNOSPERMS Introduction – Gymnosperm means “naked seed”(From the Greek: gymnos naked; sperm seed) More advanced than ferns – do not have spores,they have seeds. The seeds of the gymnosperms lack a protectiveenclosure (unlike flowering plants which haveflowers and fruit). Examples of gymnosperms: Conifers (pine trees), cycads,ginkgo biloba
Evolution of gymnosperms Gymnosperms evolved from fern-like ancestors Advancements of gymnosperms over ferns: 1. (plant embryo, food storagetissue, and seed coat) 2. Gymnosperms do not depend on water forfertilization (have air-borne pollen) 3. Have a more dominantgeneration 4. Have a more efficient vascular system
Gymnosperm life cycle Exhibits alternation of generations Sporophyte generation (2n) is dominant Gametophyte generation (1n) is contained in and dependent onthe sporophyte generation
Gymnospermlifecycle
Sporophyte generation Sporophyte produces two types of spores(heterosporous) Megasporangium – undergoesmeiosis to produce megaspores(female gametophyte) sporangium – undergoesmeiosis to produce haploid microspores,germinate to produce male gametophyte (pollen) Many gymnosperms use windfor pollination and seed dispersal
Wood produced by gymnosperms Gymnosperms have a very efficient andeffective vascular system Usually woody plants Xylem wood of a tree Phloem bark of the tree Wood is formedfrom secondary growth
Primary vs. secondary growth 1. Primary growth – occurs inapical meristems of shoots and roots Results in increase in length 2. Secondary growth – derivedfrom secondary or lateral meristems Results in increase in girth (width) Common in trees (wood and bark)
Secondary growth The cambium forms secondaryxylem and secondary phloem W – is secondary xylem; cells are dead atmaturity and only cell wall remains Bark – is secondary phloem (conducts food)
Annual rings Annual rings – xylem formed by the vascularcambium during one growth season Early Spring wood – vessel diameter is large,xylem walls are thinner Late Summer wood – vessel diameter is small,walls are thicker Tropical trees:have no annualrings, becauseseasons are sosimilar
Vascular tissue: Trees Vascular tissue is located on the outer layersof the tree.barkVascularcambiumwood
Gymnosperms Conifers are most important group ofgymnosperms Largest and most familiar group Bear seeds in cones Staminate cones – male cones Ovulate cones – cones Seeds produced on an open scale (Do not produce flowersor fruit)
Gymnosperms Mainly woody plants that include Oldest living trees: bristlecone pine,5000 yrs old! Most massive trees(giant sequoia):up to 375 ft. tall,41 ft wide! Tallest living trees (redwoods)
Conifers Conifers adapted to temperate to cold regions Narrow leaves (needles) help to conserve water Covered by resins – for protection frompredators, fire, etc.
Other gymnosperms Cycads – short shrubs,native to tropical regions(look like palms) Ginkgo biloba –a “living fossil”,male and female tree,used as a medicinal plant
Other gymnosperms Welwitschia – a bizarre gymnosperm plant that growsin Namib desert (So. Africa). Live up to 2000 years in these extreme conditions! Only makes two leaves throughout its life. It takeswater from sea mist
Significance of gymnosperms Ecological importance:Provide food and habitat for wildlifeForests prevent soil erosionReduce greenhouse-effect gassesEconomic and commercial importance:Lumber for wood, paper, etc.Resins – wood, furniture, etc.Ornamental plants (trees, landscaping)Food – pine nuts (pesto, etc.)
ANGIOSPERMS Angiosperm means “covered seed”Have flowersHave fruits with seedsLive everywhere – dominant plants in the world260,000 species (88% of Plant Kingdom)Angiosperms are the most successful andadvanced plants on earth
Evolution of Angiosperms Advancements over gymnosperms:Angiosperms have flowers – many use pollinatorsFruits and seeds – adapted for dispersalDouble fertilization of the endosperm in the seed
Angiosperm life cycle Flower has male and female sex organs
Flower structure Male sex organs: Stamens, composed of anther –organ that produces pollen (male gametophyte) Female sex organs: The carpel Ovary is the enlarged basal portion of carpel thatcontains the ovules (female gametophyte) The stigma is thereceptive portion ofthe carpel for pollengrains to adhere
Flower structure Non-reproductive parts: Sepals (green) are theoutermost whorl of leaf-likebracts Petals (usually colored) arethe inner whorl of leaf-likebracts Both can have variousshapes and colors Tepals -
Angiosperm life cycle Heterosporous: forms two different types ofspores (micro- and megaspores; male andfemale spores) Male – pollen grains contain tube nucleus andgenerative cell (2 sperm nuclei) Female – female gametophyte contains egg and2 polar nuclei
AngiospermlifecycleFlowering plants exhibitalternation ofgenerations. The large,familiar flowering plantis the diploidsporophyte, while thehaploid gametophytestages are microscopic.The unique featureabout the life cycle offlowering plants is adouble fertilization thatproduces a diploidzygote and a triploidendosperm or nutritivetissue.
Double fertilization Pollen grain germinates on stigma forming apollen tube, which grows down style to the ovary Pollen has 2 haploid sperm nuclei, which travel tothe ovary One sperm nucleus fertilizes the haploid eggforming the 2n zygote Another sperm nucleus unites with the 2 polarnuclei, forming the triploid (3n) endosperm
Seeds Fertilized egg grows into a , whichgrows into plant embryo Endosperm is stored food tissue – for theembryo to grow Mature ovule becomes the seed coat and/or fruit
Monocot vs. dicot Angiosperms are divided into monocots anddicots As the zygote grows into the embryo, the firstleaves of the young sporophyte develop and arecalled as cotyledons (seed leaves) Monocots have one cotyledon (corn, lily, etc). Dicots have two cotyledons (bean, oak, etc).
Comparing monocot vs. dicot plantsFEATUREMONOCOTSDICOTSCotyledons12Leaf venationparallelbroadRoot systemFibrousTapIn 3’sIn 4’s or 5’sScatteredArranged in acircleEitherNumber offloral partsVascularbundle positionWoody orherbaceousHerbaceous
Monocot vs. dicot Number of cotyledons: one vs. two
Monocot vs. dicot Leaf venation pattern: Monocot is parallel Dicot is net pattern
Monocot vs. dicot root Monocot: Fibrous root Dicot: Tap root
Monocot vs. dicot Flower parts: Monocot: in groups of three Dicot: in groups of four or five
Monocot vs. dicot Vascular bundle position: Monocot: Dicot: arranged in a circle
Monocot vs. dicot Stem type: Monocot: Herbaceous Dicot: herbaceous or woody
Summary: Monocot vs. dicot
GYMNOSPERMS Introduction –Gymnosperm means “naked seed” (From the Greek: gymnos naked; sperm seed) More advanced than ferns –do not have spores, they have seeds. The seeds of the gymnosperms lack a protective enclosure (unlike flowering plants which have flower
THE GYMNOSPERMS Seed Plants Gymnosperms Produce Pollen unlike bryophytes & ferns contains male gametophyte dispersed primarily by wind Produce Seeds unlike bryophytes & ferns precursor “contains” the female gametophyte and then the sporophyte embryo Gymnosperms
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Tuesday Lecture: Seedless Vascular Plants (i) Lab: Seedless Vascular Plants Thursday Lecture: Seedless Vascular Plants (ii) 10 March 15 March 16 March 18 Plant Quiz 2 (2%) Bryophyte Drawing (1%) Tuesday Lecture: Gymnosperms (i) Lab: Gymnosperms Thursday Lecture: Gymnosperms (ii) 11 March 22
Gymnosperms A gymnosperm is a vascular plant that produces seeds lacking an outer fruit. Normally these seeds are contained in cones. Gymnosperms have male and female cones. The male cones produce sperm, which are contained in pollen grains. Male cones are normally smaller than femal
The Gymnosperms Gymnosperms are simply seed plants that are not angiosperms. This means that they are grouped by what they don’t have. Gymnosperms do not bear fruits and their seeds are not enclosed. ‘Gymnosperm’ literally means naked-seeded as their seeds are not enclosed in fru
Along with other plants that reproduce by seeds (some plants reproduce by spores, not seeds), trees . (cone-bearing trees); pines, spruces, and firs are gymnosperms and conifers (Table 1). Table 1. Typical characteristics of angiosperms and gymnosperms. . of the state, or about 62 percent, were classified as forestland (which is commonly .
3 INTRODUCTION Botanists divide seed-bearing plants into two groups angiosperms and gymnosperms. Angiosperms bear true flowers and fruits.The male reproductive structure is the stamen.The female reproductive consists of one or more carpels. The usually enlarged base the carpel, termed the ovary, co
repair genes) in the datasets created in this research are as follows: ageing-related DNA repair genes‟ protein products tend to interact with a considerably larger number of proteins; their protein products are much more likely to interact with WRN (a protein whose defect causes the Werner‟s progeroid syndrome) and XRCC5 (KU80, a key protein in the initiation of DNA double-strand repair .
