Plant Anatomy Final Review: Roots, Leaves, and Flower Structures - Prof. Marisa S. Otegui, Study notes of Botany and Agronomy

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Roots  Exarch tissues – protoxylem grows toward the outside of tissue  RAM o Closed-type has a vascular cylinder, cortex and root cap o Open-type has all regions (or at least the cortex and cap) are given rise from the mass of meristematic cells  Quiescent center o It divides much more slowly o Provides new initials for meristems o Inhibits differentiation of meristematic cells  Root cap o Protects RAM o Secretes mucilage – lubricates root path o Senses gravity o Organization  Peripheral cells (mucilage secretion)  Columella cells (gravity sensation)  Amyloplasts act as statoliths  Lateral roots o Form from the pericycle  Pericycle is one layer of cells  One group of founder cells divide (hormonally signaled)  Periclinal (parallel to organ development) division  Monocot roots o Do not develop roots from the embryonic root o Can come from aerial parts or leaves, etc.  These are called adventitious roots  Arise from parenchyma or phloem  Grow the same way lateral roots do  Physical connection between xylem cells in root and in root lateral growth  Secondary vascular tissues o Vascular cambium development at outer points of xylem organ comes from pericyclic growth o Periderm grows as endodermis is sloughed-off o Pericycle also gives rise to cork cambium  Unusual growth o Sugar beet secondary growth  Unusual coordination  Several concentric layers of xylem, phloem and parenchyma  New vascular cambium forms in parenchyma  This continues growth of parenchyma for sugar storage  Terms o Velamen – multiseriate epidermis in aerial roots (water loss prevention)  Stems which resemble leaves  Leaves o Everything above axillary bud and petiole is part of single leaf o Tissues  Mesophyll  Palisade – upper part beneath epidermis  Spongy – lower part beneath palisade  Transfusion tissue  Gymnosperms only  Lies between palisade and spongy mesophylls  Arises from procambium  Isolateral leaves – palisade mesophyll on both sides as the leaves are vertical and both sides receive sun o Respiration  Photorespiration  1 molecule of 3-phosphoglycerate and 1 molecule of phosphoglycolate  Reduces the efficiency of photosynthesis by half  C4 Metabolism  In conditions favoring photorespiration, C4 respiration is likely to have resulted (ie. High O2/CO2 ratios, high light, high temps)  Phosphoenolpyruvate is carboxylated and loses a phosphate; becomes oxaloacetate which moves to the bundle sheath to lose CO2 and remaining pyruvate goes back to mesophyll  C4 plant anatomy is indicated by mesophyll organization around bundle sheaths o Modifications  Tendrils – contain cells capable of sensing contact with other objects  Carnivorous Plants  Floral Whorls - highly modified fertile leaves  Gynoecium [G] (carpels)  Androecium [A] (stamens)  Corolla [C] (petals) - perianth  Calyx [K] (sepals) - perianth  Receptacle  Pedicel  Flowers o Highly modified shoots (all floral parts derived from leaves) o Sexual reproduction o Architecture  Attraction of pollinators  Strategies to prevent self-pollination  Strategies to favor cross-pollination  Phylogenetic background o Variation  Whorls (verticils) or spirals  Fixed number or variable number  Fusion  Same whorl (connation; apo- or syn-)  Adjacent whorl (adnation)  Complete [KCAG] or incomplete  Perfect (bisexual: A and G) or imperfect (unisexual: A or G) o Symmetry  Radial – 2 or more planes of symmetry  Bilateral – 1 plane of symmetry  Asymmetrical – no planes of symmetry o Perianth – Corolla and Calyx  Functions  Protection  Attraction of pollinators  Morphology  Sympetalous corolla – all petals fused o Androecium  Stamen – anther and filament  Anther  Anatomy - connective tissue, vascular bundle, pollen sacs  Dehiscence o Longitudinal – from tip to filament o Poricidal – one large pore  Leads to pollen release  Tapetum becomes binuclear  Tapetum collapses with middle layers  Endothecium has developed striped secondary walls  Anthers dehisce, endothecium opens laterally  Tapetum nourishes microspores  Megaspore mother cell (diploid) – undergoes meiosis  Megaspores (4; haploid) – undergo mitosis and differentiation  Embryo sac – undergoes mitosis o Polygonum  Central cell – binucleate (fuse to form diploid nucleus)  Egg cell (haploid)  Antipodals – on chalazal end  Synergids – near egg cell on micropylar end (hormonally attract pollen tube)  Megasporogenesis  Meiosis I may end in a binuclear cell as there is no cytokinesis  After meiosis II, a tetraspore is formed, also due to no cytokinesis  Pollination o Bee pollination  Bilateral symmetry  Landing surface  Vivid colors (yellow, blue)  Fresh odors  Rewards (pollen, nectar) o Bird pollination  No landing surface  Vivid colors (reds)  Reward (nectar w/ high concentration of sucrose in deep corolla tubes or spurs  No nectar guides  No odors o Butterfly pollination  Vivid colors  Reward (nectar in narrow, deep corolla tubes or spurs)  Nectar guides  Weak odors o Bat pollination  Cream or white colors  Rewards (pollen, very viscous, highly sugary nectar)  Very strong odors  Flowers open at night  Strong flowers or inflorescences o Deceptive flowers – sexually deceptive  No rewards  Flowers mimic female bees  Scents mimic female pheromones  Pollen in pollinia, contacted during attempted copulation o Deceptive flowers – carrion  Pollinated by flies  Unpleasant scent resembles decaying flesh  Fruits o Berries  True berries  Fleshy endocarp and mesocarp  Skin-like exocarp (pericarp)  One or many seeds  Hesperidium  Axile placentation  Glandular endocarp (fruit of orange, lemon, etc.)  Derived from superior ovary  Mesocarp is pith  Exocarp (pericarp) is skin (has oil glands)  Pepo  Axile placentation  Anatropous position of micropyle allows micropyle to be close to emerging pollen tube  PT’s are very good at sensing micropyle  One male gamete fertilizes egg cell  One male gamete fertilizes central cell o Embryogenesis  Zygote forms embryo (new plant body)  Endosperm mother cell forms endosperm (nutrition)  Ovule integuments form seed coat (protection)  Phases  Proembryos – embryo proper attached to suspensor  Globular – embryo cells divide, suspensor enlarges and divides  Heart  Torpedo – cotyledons emerge  Late torpedo – huge endosperm vacuole diminished by growing embryo  Germination o Epigeous  Radicle emerges and becomes root  Hypocotyl grows and emerges as a loop from ground  Cotyledons emerge and pop upward  Leaves develop above cotyledons (epicotyl between) o Hypogeous  Radicle emerges and becomes root  Hypocotyl grows below ground  Epicotyl emerges and forms leaves  Cotyledons never emerge 12/18/2012
12/18/2012