BIOL 317: Plant Identification and Classification Summer Notes

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1 BIOL 317: Plant Identification and Classification Summer Notes Week 2 Tuesday Understanding phylogenies (cont.) Polarity direction of evolutionary change outgroup comparison some terms: ingroup taxon of interest outgroup taxon outside of ingroup but closely related; ideally the sister group to the ingroup character state found in outgroup is assumed to be ancestral state; alternative state is derived (change is from ancestral to derived state) other methods of determining polarity using fossil record older fossils have ancestral state assume states changed from simple to complex assume the more common state is ancestral look for correlations between character states Plant morphology the form and structure of plants Vegetative morphology parts of plants involved in growth, development, photosynthesis, support 2 organ systems and 3 organs, which differ in anatomy and development Root system usually belowground roots involved in water and mineral update, anchorage taproot one main root with smaller lateral roots fibrous main root and many lateral roots of roughly equal size adventitious roots that develop from shoot system modifications: form symbioses with soil microbes eg. root nodules housing N- fixing bacteria food storage eg. carrots support eg. adventitious roots on vines Shoot system usually aboveground stems involved in vertical growth, support node part of stem where leaf is attached internode part of stem between nodes modifications: stolon horizontally growing stem aboveground for vegetative propagation rhizome horizontally growing stem underground for vegetative propagation; sometimes thickened for food storage bulb short shoot with thickened leaves for food storage corm vertically compressed and thickened stem for food storage

2 tuber section of rhizome thickened for food storage cladode - flattened stem for photosynthesis thorn - sharpened shoot for protection leaves involved in photosynthesis always associated with an axillary bud parts of leaf blade broad flattened area for photosynthesis petiole slender stalk that attaches blade to stem (leaves without petioles are sessile) stipule paired, usually blade- like structure at base of leaf; in some, not all, leaves veins - usually there is a central, more prominent vein called the midvein or midrib leaf types: simple - blade undivided palmately compound - blade divided into leaflets, which all come off one central point pinnately compound - blade divided into leaflets, which come off central axis ternately compound - blade divided into three leaflets (also called trifoliate) leaf arrangement/phyllotaxy: alternate - one leaf per node opposite - two leaves per node whorled - three or more leaves per node basal - leaves tightly grouped together at base of plant; arrangement is actually one of the three above, but internodes are too short to allow us to tell; eg. dandelion leaf venation: secondary veins - palmate - pinnate - parallel smallest veins - reticulate/net- veined - parallel shape of leaf includes the overall shape, leaf tip, leaf base, and leaf margin (see Vegetative Morphology lab handout) modifications: colored for pollinator attraction bud scales - small, hardened leaves for protection of buds spines - sharpened leaves for protection

3 bud embryonic shoot system, with its own developing stem, leaves, and buds apical/terminal at tip of shoot; continues to elongate shoot axillary/lateral in axil between top of leaf and stem; grows into lateral/side shoot fun note: sharpened projections from the epidermis are called prickles; e.g. rose "thorns" Reproductive morphology parts of plants involved in sexual reproduction Flower - compressed shoot, usually with four whorls of modified leaves idea that the parts of flower are modified leaves was first articulated by Johann Wolfgang von Goethe ( ), German writer and scientist four whorls of flower, from outside to inside, or bottom to top: sepals (collectively, the calyx) - usually greenish, protect inner whorls when flower is in bud petals (collectively, the corolla) - usually colorful, attract animal pollinators perianth - collective term for both the calyx and corolla tepals - term used for perianth organs when outer two whorls look alike stamens (collectively, the androecium) - serve male function anther - broad sac- like structure producing pollen inside filament - stalk connecting anther to point of attachment pistils (collectively, the gynoecium) - serve female function stigma - tip of pistil that is receptive to pollen style - stalk connecting stigma to ovary ovary - broader structure containing ovules/seeds

4 other parts of flower: peduncle - stem leading to flower, when flower is solitary pedicel - stem leading to flower, when flower is part of inflorescence in this case, the peduncle is the stem leading to the inflorescence receptacle - end of stem where whorls of flower are attached some terms for flowers: complete - has all four whorls incomplete - is missing one or more whorls perfect - has both stamens and pistils imperfect - is missing stamens and/or pistils staminate - has stamens, is missing pistils pistillate - has pistils, is missing stamens some terms for species with imperfect flowers - monoecious - both staminate and pistillate flowers on same individual plant - dioecious - staminate and pistillate flowers on separate plants floral symmetry radial - has multiple planes of symmetry flower with radial symmetry is actinomorphic or regular bilateral - has one plane of symmetry flower with bilateral symmetry is zygomorphic or irregular fusion of organs connate - when organs of same whorl are fused to each other gamopetalous/sympetalous - flower with connate petals polypetalous - flower with free petals adnate - when organs of one whorl are fused to those of another epipetalous stamens - stamens are fused to petals pistils vs. carpels pistil - distinct structure with its own ovary, style, stigma carpel - subunit of pistil simple pistil - equivalent to single free carpel - there may be one or more per flower compound pistil - composed of multiple fused carpels - there can only be one per flower - is evidenced by multiple stigma lobes, multiple styles, and/or multiple chambers in ovary ovary position superior - ovary is above where other whorls of flower are attached flower is hypogynous if other whorls are directly attached below ovary flower is perigynous if other whorls are attached to a cup- like structure (hypanthium) which is attached below ovary inferior - ovary is below where other whorls of flower are attached flower is epigynous

5 placentation - where ovules are attached inside ovary some terms for structures: septum - wall of tissue dividing ovary crosswise locule/cell - chamber or section inside ovary; there may be only one if ovary if undivided (no septum), or more if divided placenta - tissue where ovules are attached marginal - in simple pistil, ovules are attached to one side of ovary wall parietal - in compound pistil, ovules are attached to multiple sides of ovary wall axile - in divided ovary, ovules are attached to central part of septum free- central - in undivided ovary, ovules are attached to central column basal - ovules are attached to base of ovary

6 Week 2 Thursday Reproductive morphology (cont.) Inflorescence - structure made of multiple flowers determinate - inflorescence shoot ends in flower which is produced first, additional flowers are produced on lateral shoots; usually center or upper- most flower opens first cyme - determinate inflorescence indeterminate - inflorescence shoot continues to grow, flowers are produced on lateral shoots; usually outer or lower- most flower opens first spike - flowers lacking pedicels (sessile) on elongate shoot head - flowers lacking pedicels on compressed shoot raceme - pedicellate flowers on elongate shoot panicle - compound inflorescence, i.e. raceme of racemes corymb - flat- topped inflorescence in which pedicels attach at different points along inflorescence shoot; pedicels differ in length to reach same level umbel - flat- topped inflorescence in which pedicels attach at same point at tip of inflorescence shoot; pedicels roughly equal in length Fruit - mature ovary containing seeds fleshy - at least part of ovary wall becomes fleshy; animal- dispersed berry - ovary wall is roughly homogenous in texture; usually many seeds per fruit; eg. kiwi drupe - ovary wall has outer fleshy layer and inner hard, stony layer; one seed per fruit; eg. cherry dry - ovary wall becomes dry; may be dispersed in various ways indehiscent - ovary wall does not split open; seeds are not released from inside ovary - achene - one- seeded with no special modifications to ovary wall - samara - one- seeded with enlarged wing on ovary wall for wind- dispersal dehiscent - ovary wall splits open to release seeds - follicle - from simple pistil - capsule - from compound pistil when several separate ovaries combine to form fruit structure multiple - ovaries from multiple flowers combine; eg. pineapple aggregate - ovaries from single flower combine; eg. blackberry Seed - mature ovule containing embryo cotyledon - first leaf or leaves of embryo, often thickened to provide food for embryo after germination; also called seed leaves radicle - young root of embryo plumule - young shoot of embryo seed coat - layer of tissue surrounding embryo, comes from integument

7 Converting phylogenetic tree to phylogenetic classification scheme only monophyletic groups should be named not all monophyletic groups have to be named rank of named taxon is arbitrary different ranks within a group are different in relative inclusiveness, but the same rank in different groups are not necessarily equivalent ranks do not correlate with a specific amount of species diversity, morphological diversity, age, etc. Evolution of plants (up to seed plants) Plants or Viridiphytes include the green algae and land plants Land plants or Embryophytes include the bryophytes and vascular plants Living on land, versus in water, presented a new set of challenges: desiccation, difficulty in exchanging nutrients between the body and the environment, less support in holding up the body A suite of innovations evolved in the ancestor to land plants that enabled them to deal with these challenges cuticle - waxy layer on body surface reduces water loss sporopollenin - resistant chemical makes up wall of propagules that allow them to be dispersed through air retained embryo - zygote formed after fertilization is retained on the mother plant, where it is protected and nurtured stomata - occurs in some bryophytes (mosses and hornworts) and all vascular plants - holes on body surface which can be opened or closed allow for controlled gas exchange between the body interior and the environment Bryophytes, or non- vascular plants, include liverworts, mosses, and hornworts Vascular plants or Tracheophytes include seedless plants and seed plants Vascular plants were able to grow larger and more complex with the evolution of: tracheids - specialized cells for water transport, with elongate shape and thickened cell walls. They form strands in bundles or rings, called xylem tissue, which conduct water throughout the plant body and give it structural support megaphylls - occurs in monilophytes and all seed plants usually large, complex leaves with multiple vascular strands. Lycophytes have microphylls, leaves with a single vascular strand Seedless vascular plants include lycophytes (club mosses) and monilophytes (ferns, horsetails)

8 Seed plants or Spermatophytes include the gymnosperms and angiosperms Seed plants became less dependent on water for reproduction with the evolution of: pollen sperm- producing structure is encased in a protective sporopollenin wall, which allows it to be dispersed in air or by animals to the female organ of other plants seeds - dormant embryo is encased in a protective coat and provided with food, allowing it to be dispersed Gymnosperms include the conifers, cycads, ginkgo, and gnetophytes. Flowering plants or angiosperms - Innovations: flower - compressed shoot, usually with four whorls of modified leaves specialized for sexual reproduction fruit - ovary encloses and protects ovules/seeds embryo sac - structure in ovule producing egg cell is reduced; usually consists of only seven cells, one of which is the egg cell double fertilization - two fusion events involving sperm; male gametophyte produces two sperm cells fusion of sperm and egg produces zygote (embryo) fusion of sperm and central cell produces endosperm (nutritive tissue for developing embryo) bitegmic ovule - two layers of integuments (protective tissue) surround embryo sac sieve tube cells (phloem) and vessel elements (xylem) - derived cell types provide more efficient transfer of food (phloem) and water (xylem) through plant body

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