Announcements: Arb field trip next week on Th, Fr, Sat; sign up for a time this week or next. First lab quiz next week on Wednesday

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1 Week 2; Monday Announcements: Arb field trip next week on Th, Fr, Sat; sign up for a time this week or next. First lab quiz next week on Wednesday Plant Morphology - form or structure of a plant and its parts ( Anatomy in Zoology) Plant Anatomy - cell and tissue structure of a plant ( Histology in Zoology) Vegetative morphology - any portion of a plant that is involved in growth, development, photosynthesis, support, etc., but NOT involved with sexual reproduction. Example: roots, stems, leaves, seeds, etc. Lecture: Vegetative Morphology (to be delivered by TAs in lab) Reproductive morphology - any portion of a plant that is involved with sexual reproduction Example: flowers, fruits, seeds, etc. Vegetative Morphology [see web lab exercise; Judd et al , 91] Seed The seed contains a young plant in which development is arrested and the plant is dormant. From the seed emerges a stem, or plumule, and a primary root, or radicle. Food is stored in the seed in the endosperm (3n) or in the cotyledons. Roots If the primary root persists, it is called a true root and may take the following forms: taproot - single main root with small lateral roots fibrous roots - many divided roots of +/- equal size. If the primary root dies (or even if it persists in some plants) new roots may arise from the stem. These are called adventitious roots. All roots on monocots are adventitious roots Stems At the tip of the growing shoot is a terminal bud or apical bud. A bud has bud scales surrounding it to protect the developing parts inside. Inside a bud are leaf primordia, lateral bud primordia, and the apical meristem. The apical meristem is responsible for new terminal growth. Page 11

2 Below the terminal bud regions of the stem may be identified as follows: node - point of attachment of a leaf lateral bud - always found in the axil of a leaf (between the leaf and stem, upward on the stem from the point of attachment of the leaf) internode - region of the stem between two nodes. Modified stems: rhizome - underground laterally growing stem (ginger) tuber - swollen elongate underground stem; modified rhizome (potato) bulb - underground stem with many swollen leaf bases surrounding it (onion) corm - swollen round underground stem (many flowering bulbs ) stolon runner or rhizome above the soil (strawberry plants) Leaves At the point of attachment of the stem to the leaf there sometimes is a small leaf-like structure attached to the stem called a stipule Leaf structure: blade - the broad part of the leaf petiole - the slender part of the leaf that attaches the blade to the stem margin - the edge of the blade; may be smooth or variously shaped ribs - vascular bundles or veins in the leaf; the central one is the midrib Leaf Shape: simple - undivided blade compound - blade divided into leaflets, each resembling a leaf; a leaf may compound more than once. You can tell a compound leaf from a simple leaf, by looking for an axilary bud at the point of attachment of each blade. If you find one the leaves are simple, if not, they are compound (there should be one at the base of the compound unit, however). dissected, or divided - blade lobed, but not all the way to the midrib. pinnate - veins arranged like pinnae on a feather palmate - veins arranged like fingers radiating from the palm of your hand Leaves may be pinnately of palmately compound, however when there are three leaflets it may be impossible to tell which. In that case the leaves are called ternate. Venation (arrangement of veins) - net veined - a branching, divergent and often reticulate pattern may be palmate or pinnate - parallel veined - primary veins all parallel as in grass Leaf Arrangement (attachment of leaves to stem) Alternate one leaf per node Opposite two leaves per node on opposite side of stem Whorled more than two leaves per node Page 12

3 Reproductive Morphology [Judd et al. pp ; 85-94] Angiosperms ( clothed seed plants) are characterized by the presence of flowers and, more specifically, the presence of a structure called a carpel which encloses the seed Flowers consist of a series of parts that are modified leaves. Goethe (Germany; ) suggested that flower parts are modified leaves (1790 in Metamorphosis of Plants). Flower Parts Pedicel modified stem leading to the flower Receptacle end of stem on which flower is borne sepals - outer (lower) whorl of parts; often greenish - function to protect, photosynthesize, attract pollinators calyx - collective term for sepals of one flower petals second whorl of parts; often colorful - function to attract pollinators, but often missing in wind-pollinated plants corolla - collective term for petals of one flower Perianth collective term for calyx and petals Tepals term used for sepals & petals when they look alike stamens - pollen producing structures - provide male function in reproduction (pollen = male, or microgametophyte; sperm are produced here) - consist of long filament supporting the anther, where pollen is produced laminar stamens on some early angiosperms have no discrete anther androecium - collective term for male portion of flower carpel - ovule producing structures (ovules contain the megagametophyte; eggs are produced here) consists of swollen ovary at base, elongate style supporting the stigma at the tip, where pollen is deposited - provides female function in reproduction ovule - the egg-producing gametophyte is contained in this structure placenta - tissue lining the ovary that bears the ovules Page 13

4 Now here s where it gets confusing: Flowers may have a single carpel or many carpels; the carpels may be separate structures or fused together into a single structure pistil - generalized term for each individual female structure (may consist of one or more than one carpel) in a flower When single or separate, each carpel equals one pistil simple pistil There may be one or more than one simple pistil per flower When fused together, one pistil may consist of many carpels - compound pistil There may ONLY be one compound pistil per flower How can you tell if a pistil is simple or compound? There are two ways to tell that will work in almost all cases. 1) Look for more than one stigma lobe at the top of the pistil; compound pistils often have separate styles or lobes on the stigma. 2) Make a cross-section of the ovary and look for compartments (locules), or more than one point of attachment of the ovules, that indicate fusion of two or more carpels. gynoecium - collective term for female portion of flower (may be one or many pistils) *** In nature, there are plants with one or more simple pistils and plants with one compound pistil, but no plants with more than one compound pistil per flower. *** Inside the ovary the ovules attach to the placenta in two basic ways: parietal placentation - ovules attached along the ovary wall primitive carpel a folded megasporophyll with ovules along fused margins axile placentation - ovules attached to a central septum in the center of the ovary Variations on axile placentation include: free central - axile with the septum missing basal - derived from either axile or parietal, but only attaching at the base Locule The chamber or opening inside the ovary where the ovules are found. There is not really empty space here (although sometimes a space develops as the seeds mature in the fruit), but the ovules are only attached to the ovary wall at the placenta, thus the locule is a chamber filled with ovules. Flowers may be: complete - all four whorls present incomplete - one or more whorls missing perfect - both reproductive whorls present (bisexual) imperfect - one reproductive whorl missing (unisexual) Page 14

5 Plant species may be: hermaphroditic plants with perfect flowers monoecious - plants with imperfect flowers, in which both sexes are on the same plant dioecious - plants with imperfect flowers, in which each sex is on a separate plant In many flowers the parts in each whorl or the whorls themselves may be fused together connate - parts of one whorl fused to each other gamopetaly or sympetaly - fused petals syncarpy - fused carpels adnate - parts on one whorl fused to parts in another whorl epipetalous stamens - stamens adnate to petals The position of the ovary relative to other flower parts is often diagnostic: superior ovary hypogynous ( hypo- means under and refers to location of other parts relative to the ovary inferior ovary epigynous ( epi means over ) sometimes there is a fusion of parts at the base of the flower that makes it unclear where the ovary is relative to the attachment of the other parts and it may appear to be anywhere between fully superior and fully inferior this situation is called perigynous ( peri- means around ) Flower symmetry - Radial, regular, or actinomorphic symmetry - many planes of symmetry bilateral, irregular, or zygomorphic symmetry - one plane of symmetry Inflorescence - term for the flowering part of a plant; all of the flowers in aggregate Infructescence - Inflorescence after flowering is over and the fruits have ripened. Fruit - mature ovary - once the eggs within the ovules have been fertilized and the ovary starts to expand, it is usually called a fruit functions: [one or more of these may exist for same fruit] - dispersal of seed - nutrition for developing embryos - protection of seeds - prevent being eaten Page 15

6 Week 2; Wednesday Announcements: Next week - quiz on conifers and plant structure; Arb field trip Props for lecture today: moss with sporophytes; sword fern frond with sori Lecture: Keys, Life Cycles and Major Land Plant Groups Dichotomous Key - a progressive series of paired alternative statements that lead to the identification of an organism. - keys don t need to be dichotomous, but usually are - written keys start with a certain bit of information and progress towards an end - computer keys (only now coming into use) can start with any information - Usually most useful keys are artificial, in the sense that if you draw a dichotomous tree reflecting the branches in the key, the branches would not be monophyletic groups - leads may pair this vs. that, or may pair this vs. not this - read carefully - if more than one character is described in key lead, the most important or consistent difference usually is listed first. Review Reproductive morphology answer questions (esp. carpel/pistil terminology) Reading from J. W. Krutch, pp in The Voice of the Desert. Lecture: Life cycles and Land Plant Relationships Life Cycles (... of the rich and famous) [web readings 1-2] Generalized life cycle -overhead- (see below) - alternation of generations emphasize continuity - life is like a sine wave... Fertilization the act of fusion between sperm and egg. Fertilization occurs in all sexually reproducing organisms. In seed plants, this must follow pollination. Sporophyte the diploid (2n) generation in plants. It begins with fertilization, which produces the zygote, the first cell of the diploid generation. Cell division (mitosis) produces the embryo and, ultimately, the mature sporophyte, which makes special structures called sporangia, where meiosis takes place. Spore the product of meiosis; the first cell in the haploid (1n) or gametophyte generation in plants. [in most animals meiosis produces gametes directly] Gametophyte The haploid (1n) generation in plants. Flowering plants are heterosporous, meaning that they produce two different kinds of spores: 1) the microspore becomes the pollen grain and 2) the megaspore becomes the embryo sac. These are called the male and female gametophytes, respectively. Pollination the act of transferring pollen (male gametophyte) from anther or male cone to stigma or female cone; occurs in all seed plants, but not ferns, mosses, etc. Page 16

7 Gamete the haploid cells that participate in fertilization, egg and sperm. These are produced by specialized structures in the gametophyte generation of plants called archegonia and antheridia, respectively (collectively called gametangia). In flowering plants the gametophytes are so reduced (pollen grain and embryo sac) that distinct gametangia are not found. NOTE: In most animals the product of meiosis also functions as a gamete. Distinguish Pollination from Fertilization and Spore from Gamete mature sporophyte Fertilization embryo zygote gametes (egg and sperm) Archegonium Antheridium diploid (2n) sporophyte generation haploid (1n) gametophyte generation sporangium Meiosis spores mature gametophyte Variations on the theme... Each generation (sporophyte/gametophyte) may be: Free-living depending only on itself for nutrients Dependent depending on its parent (previous generation in the life cycle) for nutrition Usually one generation is dominant, but in some algae both are +/- equivalent. green algae - some have sporophyte dominant, some gametophyte dominant, and some are isomorphic Mosses - gametophyte dominant and free-living; sporophyte dependent Ferns - sporophyte dominant and free-living; gametophyte free-living, but small and short-lived seed plants - sporophyte dominant and free-living; gametophyte dependent and reduced Angiosperms - gametophyte VERY reduced - pollen 2-3 cells; embryo sac 8 cells Page 17

8 Land Plant Relationships -Overhead- Major groups of organisms in Kingdom Plantae (= green plants) Note that this is one view of land plant relationships. Some molecular evidence contradicts this view, suggesting that bryophytes might be related differently than shown here. Also, some evidence suggests that the extant (those alive today) gymnosperms may be monophyletic. Plantae Green Algae - paraphyletic basal group Land Plants Liverworts \ Hornworts > Bryophytes paraphyletic - consists of 3 monophyletic groups Mosses / Tracheophytes (traditionally vascular plants, However, mosses have vasculature, but not special cells called tracheids ) Lycophytes - Lycopodium (club mosses), Selaginella (resurrection plant) Fern allies Sphenophytes - Equisetum (horse tails) Psilotum Ferns - Seed Plants Cycads Ginkgo Conifers - you know these guys Gnetophytes - Gnetum, Ephedra (Mormon Tea), Welwitschia Angiosperms the rest of the quarter will be about these guys note that there is a relative time line on a cladogram, with the tips being the present Page 18

9 Land plant relationships and derived traits (synapomorphies) of major groups Page 19

10 Week 2; Friday Announcements: 1) First lab quiz next Wednesday on conifers and plant structure 2) First lecture exam in 2 weeks it will cover material through next Friday 3) Next week will be a field trip to the Arboretum; sign up for a time next week in lab Angiosperm Classification Many classifications have been proposed over the years. We generally start with Linnaeus (Species Plantarum 1753), but there were others before him. Engler and Prantl (Die Naturlichen Pflanzenfamilien, late 1800 s) treatment included 280 families and is the basis for the formal organization of most herbaria around the country today. -- Later in lab we will visit our Herbarium -- Bessey (early 1900 s) was the first American to propose a system and his was the starting point of many subsequent systems, including Cronquist and others. These are all what we call authority-based classifications [OVERHEADS] Bessey 1915 \ Stebbins 1974 \ Cronquist 1981 \ Takhtajan OVERHEADS Dahlgren 1989 / Thorne 1992 / What about now? New classifications are not authority-based classifications, but are based on phylogenetic reconstructions, which are derived from commonly agreed-upon principles and objective data. Our current view of relationships is derived primarily from the results of the analysis of DNA sequences from the chloroplast genome primarily, but increasingly from nuclear and mitochondrial genes, as well (mitochondrial genes have been used to a much greater extent in animals). e.g., Chase et al OVERHEAD; APG III OVERHEAD Page 20

11 Monophyletic origin of angiosperms. Evidence: 1) Carpel (ovary) enclosing the ovules 2) Ovules with two integuments (bitegmic ovules); integuments surround the ovule and become the seed coat) 3) Reduced female gametophytes (embryo sac) typically composed of 7 cells and 8 nucleii (the two polar nuclei occupy the same cell). After meiosis in the megaspore mother cell, 3 daughter cells abort and one becomes the megaspore, which divides three times to become the embryo sac. 4) Triploid endosperm product of double fertilization (sperm + 2 polar nuclei) 5) Sieve tubes in their phloem to conduct fluids from leaves to other parts of plants Sieve tubes have open ends and stack like straws inside the plant Within angiosperms two features may each be used to divide them into two groups: 1) Number of cotyledons (seed leaves) - one or two (monocots and dicots) 2) Number of apertures on the pollen grain - one or three (basal angiosperms and tricolpates, or sometimes called eudicots ) - OVERHEAD However, neither character splits the flowering plants into two monophyletic groups and there are some families that are left out of the groups characterized by the derived states of one cotyledon and tricolpate pollen. Page 21

12 It is important to point out that many details of the relationships among flowering plants remain unresolved However, some important groups do emerge (OVERHEAD): The most primitive plants may be either herbaceous or woody. These all have monocolpate pollen and two cotyledons: 1) Near the base of the tree are three groups of plants that are shrubs or herbs, including Amborella (one sp. from New Caledonia), Nymphaeales (water lilies), and a few odd genera from around the world sometimes called the ANITA grade (or ANA grade in Judd et al. 4 th Ed.). 2) Also near the base are some woody plants called the Magnoliales and Laurales 3) The remaining basal groups (including Piperales and Chloranthaceae) are mostly herbaceous. Along with the water lilies and monocots, these sometimes are called the paleoherbs 4) Monocots are monophyletic and derived from dicots - some shared derived characters include: single cotyledon scattered vascular bundles parallel leaf venation (or striate venation, sensu Foster and Gifford; note exceptions in some monocots However, they do have pollen with a single aperture. 5) Another important split occurs between the monocolpate and tricolpate pollen types; the latter are called Tricolpates (more commonly called Eudicots). Within the Tricolpates; there are three large monophyletic groups and several small groups at the base: 5a) Basal Tricolpates is a basal paraphyletic group within the Tricolpates 5b) Caryophyllids - This group is pretty well characterized by some distinctive features, including pigments known as betalains and seed nutritive tissue called perisperm. Flowers are polypetalous 5c) Rosidae sensu lato - contains most of the polypetalous families. This group is difficult to characterize; mostly by absence of traits found in other groups 5d) Asteridae sensu lato - contains most of the gamopetalous families (with connate petals fused into a tube around the rest of the stamens and pistil) these are characterized best by embryonic and chemical characters - tenuinucellate ovules (a thin nucellus) - single integument on the ovules (one has been lost, or the two are fused) - secondary chemical compounds known as iridoids Page 22

13 Magnoliidae" sca1ered"vascular" """""bundles" parallel"vena/on" 1"cotyledon" Perianth"of"2"whorls" Anthers"well"differen/ated"from"filaments" Page 23

Flower Morphology. Flower Structure

Flower Morphology. Flower Structure wrong 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 right 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 score 100 98.8 97.6 96.4 95.2 94.0 92.9 91.7 90.5 89.3 88.1 86.9 85.7 84.5