Plant Bio Exam 2 Study Guide Lecture 7 Objectives Know what the suspensor is and what its function is o The suspensor s function is to file and deliver nutrients from the ovule to the embryo and it is connected to the embryo Embryo is the young sporophytic plant Know the parts of the angiosperm embryo o root and shoot apical meristems Where cell division takes place The root shoot axis hypocotyl and embryonic root cotyledon Embryonic axis below attachment of cotyledons and above the radicle o Hypocotyl o Cotyledons There is two cotyledons and are the food storage organ in dicots In onions it is the first true left but in cereal grains it is a shield shaped structure that has an important role in seed germination and is not a food storage organ at all o vascular tissue ground tissue epidermis outside Vascular tissue is in the center and they develop into 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 Know what the aleurone is and what its function is in germination of cereal seeds gibberellic acid and production of amylase o The aleurone is the outer layer of the endosperm o GA from embryo stimulates aleurone layer to secrete hydrolytic enzymes amylase o Variety of functions to help maintain proper development of the seed maintaining a low pH in cereals the aleurone layer releases organic and phosphoric acids in order to keep the pH of the endosperm between a pH of 3 5 and 4 Know what parts of the cereal seed are bran and germ o wheat bran aleurone seed coat o wheat germ embryo Be able to describe the different types of seed dormancy the factors that affect seed germination and their biological role o Germination Conditions affect it water temperature Embryo stimulates aleurone layer to secrete enzymes absorption of breakdown products from endosperm by cotyledon and growth of epicotyl shoot and hypocotyl root o Quiescent seeds vs Dormant seeds Quiescent seeds only need water and permissive temperature to germinate No real dormancy Dormant seeds have factors that control germination Imposed Dormancy the seed coat is so hard and can t be penetrated by water or nutrients that the embryo can t develop scarification By nicking the seed coat you can start germination Chemical Dormancy Inhibitors are present and a cue needs to be present to start germination The most common is chilling light and fire These cues can be affected by the location since temperature can be different Fire acts as a cue since plants germinate after forest fires Know the basic parts of the seedling o Primary root tap root o Lateral roots Arise from cell divisions in the pericycle o Hypocotyl Portion of the shoot that is above of the root but below the cotyledon First part of the cell the emerges above ground in beans known as the hook The act of it straightening out is in response to light The hypocotyl might get damaged in the process but it protects the root tip o Epicotyl o Cotyledons Portion of the stem above the cotyledon First to emerges and hook in some plants Supplying energy and they will wither once the plant fully grows since all the nutrients are sucked out The hook in onions o true leaves foliage leaves o hook portion of the stem that is bent when seedling emerges from the ground Can be either hypocotyl epicotyl or cotyledon monocot Main function is protection 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 o Meristems are regions containing stem cells and where cell division is localized shoot apical meristem root apical meristem o Primary tissues are the apical meristem Epidermal Dermal tissue system o Epidermis outside Consists of epidermal cells guard cells o Ground tissue middle Consists of parenchyma cells Many different functions storage space filling or photosynthetic depending where it is found o Vascular tissue inside Consists of tracheids vessel elements xylem transports water and mineral ions Sieve tube elements companion cells phloem transport of sugars Leaf primordial Group of cells that will develop into a leaf seen as small bulges just below the shoot apex o Root Cap o Lateral buds The cells different into the roots tip and the root cap protects the root tip which dies when it pushes through the soil bud located on the side of the stem usually in a leaf axil and becomes a new stem Be able to name and describe the structure and functions of cells in Ground tissue o parenchyma cells cuboidal and have a very thin cell wall live and active cells Gives support o collenchyma cells Elongated and thick cell walls Live Gives support o Sclerids The veins in celery that we pull out are collenchyma cells Elongated and VERY thick cell walls They die once they mature by programmed cell death Vascular tissue o Xylem The upper part of the vascular tissue Transport of water and minerals o Tracheids Part of Xylem Have pits in the cell walls Dead at maturity o Vessel elements Long and tapered off so no openings at the end walls Part of Xylem are very wide and short for rapid water transport end walls are open Dead at maturity o Phloem Lower part of vascular tissue Transports sugar and amino acid o sieve tube elements Part of the Phloem Have special end walls sieve plates and they are stacked which makes Sieve Tubes Each element has a companion cell Due to uneven cell the division the larger part becomes the sieve tube element Live at maturity but contain no organelles just cytoplasm and specialized for sugar transport Supplies all metabolic support to the sieve tube element Smaller part of the cell division a vertical series of cylindrical cells in the phloem specialized for the conduction of food materials o companion cells o sieve tubes Objectives for Lecture 8 Root development and structure primary o Primary Growth Growth in length due to cell division in apical meristems followed by cell enlargement and differentiation Dicot with tap root and side roots Monocot with fibrous root system Plant Shoots are built from repeating units phytomeres o Secondary Growth is growth in girth thickness Understand the terms o zone
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