Types of leaf phyllotaxis Opposite, alternate, whorled Most leaves are either simple or compound This is connected to the stem by the petiole Leaf blade The leaf blade is connected to the stem by this Petiole Leaf parts Blade, petiole, base, margin, apex, venation This type of compound leaves are similar to ferns Pinnate leaves This type of compound leaves have leaflets attached at one point Palmate leaves The portion of the petiole in pinnate leaves that is lined with the leaflets Rachis Simple leaves: axillary buds Occur at the base of each leaf Compound leaves: axillary buds Occur at the base of each leaf - not at the base of leaflets Simple leaves: abscission layer forms at the base of the leaf's petiole Compound leaves: abscission layer forms at the base of the leaf's petiole - not at the base of a leaflet Simple leaves: phyllotaxis? Leaves have a phyllotaxis Compound leaves: phyllotaxis? Leaflets are generally all produced in the same plane Cells just under the leaf's epidermis that do the majority of photosynthesis Palisade mesophyll (palisdae parenchyma) Irregularly shaped cells above the lower epidermis of the leaf Spongy mesophyll (spongy parenchyma) Especially large motor cells in the epidermis of grass leaves that are responsible for folding or rolling of the leaf Bulliform cells An outgrowth of the leaf epidermis, which serves to minimize air flow directly adjacent to the leaf surface Trichome This covers the epidermis to attempt to minimize water loss Cuticle Physical size attributes of sun leaves Small and thick Physical size attributes of shade leaves Large and thin Carbon fixation of sun leaves Quickly in intense sunlight Carbon fixation of shade leaves 3 to 5 times slower than sun leaves Chloroplast attributes of sun leaves Many small chloroplasts per cell Chloroplast attributes of shade leaves Fewer and larger chloroplasts, but more grana per cell Leaves may do this in response to hormones triggered by environmental changes Leaf Abscission Two regions of leaf abscission Abscission layer, protective layer Plants that are adapted to arid habitats Xerophytes Water lillies have this variation Stromata on the upper surface African violets have this modification Many trichomes Carniverous plants are specialized in... obtaining mineral nutrients in wet or mineral poor habitats Cork cambium is also known as Phellogen Cork cambium produces cork (phellum) and phelloderm tissues In stems, vascular cambia is derived from a combination of cells of fascicular and interfascicular cambia In stems, cork cambia is derived from cells of the cortex In roots, vascular cambia is derived from cells of the pericycle and cells of the procambium between the xylem and phloem In roots, cork cambia is derived from from other pericycle cells The bark is also known as Periderm A difference in wood cross sections of oak and pine is Oak has thick, multiseriate wood rays Two types of regions in an Oak wood cross section Heartwood and sapwood Pores in the cork layers which allow for gas exchange in the periderm Lenticels Nettles have these leaf modifications Stinging trichomes The cuticle is made of this Cutin Apical meristems are protected by this Bud scales These are circular markings on petioles Terminal bud scale scars Densest wood Ebony Highly valued for furniture Cherry wood, black walnut wood These function as the primary absorption cells of the root Root hairs The lower part of the stem Hypocotyl This is known commonly as "Moses-in-a-boat" Rheo discolor "Moses-in-a-boat" have these pigments Anthocyanin pigments Suspensor Stalklike structure which supports the cotyledon Basal cell The large cell that anchors the suspensor Wood Secondary xylem Plant hormones are better described as Growth regulators First pioneering work on Phototropism was done by Charles Darwin and son Francis He developed the Avena Coleoptile Curvature Test Fritz Went The Avena Coleoptile Curvature Test is known as The first bioassay Substance that causes bending in plants Auxin Actual chemical name for Auxin Indole-acetic Acid (IAA) IAA's structure is composed of An Indole ring and an acetic acid group IAA's moving only downward is called Polar transport Mechanism of IAA action is called The acid growth hypothesis The fact that most growth occurs at the top of the plant is referred to as Apical Dominance Auxin can inhibit this Abscission of leaves and fruits Auxin + Gibberellins can stimulate growth of this Xylem and/or phloem Seedless fruits Parthenocarpic fruits Auxin can do this to roots Cause adventitious roots to be formed Weed killers may contain this Auxin Agent Orange contained this toxic trace molecule Dioxin Cytokinins were originally observed in this substance Coconut milk Old Herring Sperm DNA led to the discovery of this Cytokinins The first naturally-occurring cytokinin to be isolated Zeatin Most cytokinins are produced in this Roots High IAA, low cytokinin = stimulation of Shoot formation Low IAA, High cytokinin = stimulation of Root formation Climacteric In fruits such as Apples, there is a large increase in cellular respiration evidenced by an increased uptake of oxygen Used for ripening fruits artificially Ethylene Promotes flowering in some plants like mangos and pineapples Ethylene Plant aging Senescence This may induce senescence in some flowers, such as orchids Ethylene ABA was first extracted from dormant buds and called Dormin This is involved in closure of stomata Abscisic Acid (ABA) May be involved in bud dormancy Abscisic Acid Can induce seed dormancy in some plants Abscisic Acid Kurosawa discovered this while investigating Foolish Seedling disease of rice Gibberellins This can cause stem elongation Gibberellins This causes elongation and cell division throughout the plant Gibberellins This can overcome genetic dwarfing Gibberellins This is used in sugarcane production Gibberellins This can be used to stimulate seed germination in grasses Gibberellins This can substitute for winter cold period for flowering in rosette biennials Gibberellins This can be used to produce larger fruits in open clusters in Thompson seedless grapes Gibberellins