4/12/16 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 Plant Anatomy - cell and tissue structure of a plant 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 or a direct product of sexual reproduction Example: flowers, fruits, seeds, etc. Vegetative Morphology [see web lab exercise; Judd et al. 55-63] 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 10 4/12/16 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 11 4/12/16 Reproductive Morphology [Judd et al. pp. 61-67; 72-81] 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; 1749-1832) – 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 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 12 4/12/16 Now here’s where it gets confusing: Flowers may have a single carpel or many carpels; the carpels may be separate or fused together pistil - generalized term for each individual female structure 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 13 4/12/16 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 flower, 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 14 4/12/16 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.