Inflorescences Floral Displays A shift from widely spaced single flowers to an inflorescence required condensation of shoots and the loss of the intervening leaves The vast majority of flowering plants possess flowers in clusters called an inflorescence inflorescence These clusters facilitate pollination via a prominent visual display and more efficient pollen uptake and deposition The simplest inflorescence type would thus be indeterminate with the oldest flowers at the base and the younger flowers progressively closer to the apical meristem of the shoot Raceme Prunus or cherry a raceme One modification of the basic raceme is to make it compound The panicle is essentially a series of attached racemes with the oldest racemes at the base and the youngest at the apex of the inflorescence compound Raceme Panicle Panicle Zigadenus or white camass 1 A second modification of the basic raceme is to lose its pedicels The spike is usually associated with congested reduced flowers and often but not always with wind pollination Pedicel loss wind pollinated Spike Raceme Plantago or plantain Spike animal pollinated The spike is usually associated with congested reduced flowers and often but not always with wind pollination A third modification of the basic raceme is to lose its internodes Internode loss Umbel Spike Combretum Brent Brent s plants Raceme 2 The umbel characterizes specific families carrot and ginseng families for example The umbel is found scattered in many other families as well These families typically show a compound umbel smaller umbellets on a larger umbel Umbel Umbel Cicuta or water hemlock Zizia or golden alexander Eriogonum or false buckwheat family Polygonaceae Polygonaceae Ben Ben s plants A fourth modification of the basic raceme is for the stem axis to form a head The head or capitulum characterizes specific families most notably the Compositae or Asteraceae Asteraceae Not surprisingly this family is closely related to families possessing umbels Stem head Head or capitulum Head or capitulum Helianthus or sunflower Raceme 3 Besides these indeterminate inflorescences based on the raceme there is a series of inflorescence types based on determinate shoots shoot can not grow up indefinitely The simplest is the dichasium dichasium The dichasium inflorescence is terminated i e determinate by the oldest flower and flanked by two lateral younger flowers oldest flower Dichasium Dichasium Raceme younger flowers Clematis or virgin virgin s bower One modification of the basic dichasium is to make it compound The cyme characterizes specific families most notably the Caryophyllaceae the pink or carnation family compound Cyme Dichasium Cyme Silene or campion campion 4 A second modification of the basic dichasium is to reduce it or the Gentianaceae the gentian family reduction Cyme Dichasium Monochasium Lisianthius Lisianthius Another specialized inflorescence is the catkin or ament The monochasium is most often seen in compound form as a scirpoid inflorescence The Boraginaceae Virginia bluebell family is characterized by this distinctive inflorescence unisexual cluster of small flowers apetalous without petals hard bracts around the flowers wind pollinated falls as a unit Scirpoid Mertensia or bluebell male catkin female catkin Populus or cottonwood male catkin Quercus or white oak 5 A final specialized inflorescence is the spadix thickened fleshy spike associated with spathe bract frequently flowers unisexual best developed in the aroid family Araceae Araceae spathe spadix Symplocarpus or skunk cabbage Arisaema or Jack in the pulpit 6
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