Lecture 7 Objectives Know what the suspensor is and what its function is attaches embryo to ovule transports nutrients from ovule to embryo and endosperm Know the parts of the angiosperm embryo root and shoot apical meristems hypocotyl cotyledons vascular tissue ground tissue epidermis Know that in some dicots the endosperm is completely converted into cotyledons in others it is not and in some monocots the cotyledon is specialized for adsorption of nutrients from the endosperm whereas in other monocots the cotyledon simply protects the shoot as it emerges from the ground in dicots endosperm is more or less completely digested and replaced by cotyledons in monocots endosperm is retain in mature seed Know what the aleurone is and what its function is in germination of cereal seeds gibberellic acid and production of amylase know what parts of the cereal seed are bran and germ Aleurone outer layer of endosperm Cells secrete enzymes that break down the endosperm during germination The cotyledon then takes them up and helps the embryo grow Wheat bran aleurone and seed coat Wheat germ embryo Be able to describe the different types of seed dormancy the factors that affect seed germination and their biological role quiescent seeds vs dormant seeds imposed dormancy biochemical dormancy water temperature light hard seed coat blocks oxygen and water uptake presence of germination inhibitors Quiescent Seeds need only water and good temps to germinate most agricultural seeds Dormant Seeds Some factor controls germination Imposed Dormancy Hard seed coat prevents H2O uptake Chemical Dormancy Growth Inhibitors present or plant needs a chilling fire or light to grow Know the basic parts of the seedling primary root tap root lateral roots hypocotyl epicotyl cotyledons true leaves foliage leaves hook Be able to explain what a meristem is and know what structures and tissues are produced by the shoot apical meristem and the root apical meristem primary tissues epidermis ground tissue vascular tissue leaf primordial lateral buds root cap Know the functions of the root cap and the lateral buds Meristems Localized region of cell division Shoot apical meristem makes cells and tissues of shoot plus leaves and lateral buds Lateral buds are dormant shoot apical meristems can grow out into a branch Root apical meristem makes cells of body of root plus root cap Root cap protects root apical meristem as root grows through soil three primary tissues in plants epidermal ground and vascular tissues Epidermal tissue consists of epidermal cells guard cells Ground tissue consists of parenchyma cells large thin walled live cellsfunction as storage space filling or photosynthetic depending on where found Collenchyma cells that are live with thick walls for support And Sclerids fibers thick walls stiff for support and they are dead Vascular tissue consists of tracheids vessel elements xylem transport of water and mineral ions sieve tube elements companion cells phloem transport of sugars tracheids and vessel elements are dead at maturity cell wall only tracheids are long and tapering with pores pits in side walls vessel elements are short and wide with no end walls are stacked to make pipes vessels for rapid water transport sieve tube elements are live at maturity but contain no organelles just cytoplasm and specialized for sugar transport Each sieve tube element is connected to a companion cells which provide metabolic support Be able to name and describe the structure and functions of cells in ground tissue parenchyma cells collenchyma cells and sclerids Picture and in vascular tissue Xylem tracheids vessel elements vessels and Phloem sieve tube elements companion cells sieve tubes Xylem water mineral transport support Tracheids long and tapering support Phloem sugar amino acid tansport Sieve tube elements have specialized end walls sieve plates and are stacked to make sieve tubes each sieve tube element has a companion cell Objectives for Lecture 8 Root development and structure primary Understand the terms zone of cell division zone of cell elongation zone of cell differentiation Quiescent center Understand that growth in length of the plant is due to the production of new cells by the apical meristems followed by cell enlargement cell elongation Growth in length is called primary growth and tissues and cells produced by the apical meristems are primary tissues and primary cells primary xylem primary phloem etc Quiescent center stem cell population Growth in length due to cell division in apical meristems followed by cell enlargement Primary Growth Tissues made by apical meristems are primary tissues Know what the endodermis and pericycle are where they are located and how lateral roots are formed Outer cell layer of vasc cyl is endodermis cell layer just below thisis the pericycle Initiation of cell division in pericycle results in a lateral root Be able to identify a dicot and monocot root based on the organization of the vascular tissue monocot has a pith in the root dicot does not both are surrounded by an endodermis Shoot development and structure Primary Know the terms node internode lateral bud leaf primordium Node place where the stem comes off the main shoot between internodes where there is no lateral growth Lateral bud the bump just above a leaf stem Leaf Primordium leaflets just next to the apical meristem Know the 3 layered structure of the shoot apical meristem two tunica layers and a corpus understand the difference between anticlinal and periclinal divisions and their importance to maintenance of the meristem s structure Anticlinal adds cells to the sides Periclinal adds cells below shifts from anticlinal to periclinal Know that leaf primodia are formed when the plane of cell division in the inner tunica layer Know which layers of the shoot apical meristem give rise to the epidermis the cortex the vascular tissue and the pith Outer tunica layer epidermis Inner tunica layer cortex and vascular tissue Corpus vascular tissue and pith Be able to identify a monocot and a dicot stem based on the organization of the vascular tissue monocot has no pith and has many vascular bundles throughout the diameter of the stem the dicot stem has a ring of vascular bundles between the cortex and pith also stems do not have an endodermis See above picture Leaf structure Know the following terms petiole blade midrib lateral veins simple leaves compound leaves mesophyll palisade parenchyma spongy parenchyma guard
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