BIOL 317: Plant Identification and Classification Summer 2015 - Notes Week 2 – Tuesday Understanding phylogenies (cont.) • Different kinds of groups • Monophyletic group = clade • includes ancestor and all descendents • characterized by synapomorphies – shared derived traits – evolved in common ancestor of group and is found in all descendents • only kind of group tHat sHould be named in phylogenetic classification § gives classification scHeme predictive power – all members of named groups have closest relatives within group • examples: spermatopHytes, tracHeopHytes, embryopHytes • Paraphyletic group • includes ancestor and some descendents • characterized by symplesiomorphy – shared ancestral traits – evolved in common ancestor of group but was lost or changed in some descendents • example: bryopHytes (symplesiomorpHy: non-vascular condition) • Polyphyletic group • includes multiple lineages witHout tHeir common ancestor • characterized by homoplasies (analogies/convergences) – traits that evolved independently in multiple lineages • example: group combining land plants and fungi (Homoplasy: sessile terrestrial lifestyle) • 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 • 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. 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 • 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: • primary 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 • 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" Week 2 – Thursday Plant morphology (cont.) • 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 (1749-1832), 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 • 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 - is missing pistils • pistillate - 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 § bitlateral - 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 • 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 • Inflorecence - 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