BOT3015 Exam 2 Study Guide Lectures 7 10 Lecture 7 Seeds Seed Dormancy Meristems Plant Tissues Know what the suspensor is and what its function is Suspensor A structure at the base of the embryo in many vascular plants that anchors the embryo at the micropyle opening the ovule through which the pollen tube enters Delivers nutrients from the ovule to the embryo Apical embryo Basal suspensor Know the parts of the angiosperm embryo root and shoot apical meristems hypocotyl cotyledons vascular tissue ground tissue epidermis Root and shoot apical meristems are found at the tips of all shoots and roots and are composed of cells that are capable of repeated division Meristems are perpetually embryonic tissues apical meristems are involved with extension of the plant body 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 angiosperm dicot embryos the apical meristem of the shoot arises between the two cotyledons in monocot embryos on the other hand the shoot apical meristem arises on one side of the cotyledon and is completely surrounded by a sheath like extension from the base of the cotyledon Know what the aleurone is and what its function is in germination of cereal seeds Aleurone a proteinaceous material usually in the form of small granules occurring in the outermost cell layer of the endosperm of wheat and other grains Know the basic parts of the seedling primary root tap root lateral roots hypocotyl epicotyl cotyledons true leaves foliage leaves hook Understand the terms epigeous and hypogeous Monocot dicot Primary root tap root the first root of the plant developing in the continuation of the root tip or radical the embryonic root of the embryo the taproot In dicots the primary root termed taproot grows directly downward giving rise to branch roots or lateral roots lateral roots a root that arises from another older root hypocotyl the portion of an embryo or seedling situated between the cotyledons and the radicle the stemlike axis below hypo the cotyledon s epicotyl a stemlike axis in the embryonic shoot that occurs above epi the cotyledon s cotyledons The cotyledon provides nutrients for the germinating plant true leaves foliage leaves real leaves that form after the germination of the cotyledon s hook the bend of the shoot during germination Eventually pulls the cotyledons and plumule up into the air and out of the ground epigeous type of seed germination in which the cotyledons are carried above ground level hypogeous type of seed germination in which the cotyledons remain underground Seed Dormancy Quiescent Seeds need only water and permissive temperature to germinate Dormant Seeds some factor controls germination Imposed Dormancy Hard Seed Coat prevents water or O2 uptake scarification Chemical Dormancy Growth inhibitors present coumarin abscisic acid or some particular cue need chilling light fire 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 Shoot apical meristem gives rise to ground tissue dermal vascular tissue leaf primordial Root apical meristem gives rise to ground tissues dermal tissue vascular tissue lateral roots root cap Be able to name and describe the structure and functions of cells in ground tissue parenchyma cells collenchyma cells and sclerids and in vascular tissue Xylem tracheids vessel elements vessels and Phloem sieve tube elements companion cells sieve tubes Ground tissue consists of parenchyma collenchyma and slerenchyma collenchyma cells supportive tissue that supports young growing organs They are living at maturity like the parenchyma cells Because they are living at maturity the can continue to develop thick flexible walls while the organ is still elongating making these cells especially well adapted for the support of young growing organs Common in regions of primary growth in stems and in some leaves parenchyma cells living generally thin walled cell of variable size and form the most abundant kind of cell in plants Involved in photosynthesis storage and secretion activities dependent upon living protoplasts Because they retain their meristematic ability parenchyma cells having only primary walls play an important role in regeneration and wound healing In addition parenchyma cells may play a role in the movement of water and the transport of food substances in plants They occur as vertical strands of cells in the primary and secondary vascular tissues and as horizontal strands called rays in the secondary vascular tissues sclereids a sclerenchyma cell with a thick lignified secondary wall having many pits Sclereids are variable in form but typically not very long they may or may not be living at maturity The principle characteristic is their thick often lignified secondary walls two types of sclerenchyma cells fibers generally long slender cells that occur in strands or bundles sclereids variable in shape often branched relatively short cells Vascular tissue Xylem the principal water conducting tissue is also involved in the conduction of minerals in support and in food storage In the primary plant body the xylem is derived from the procambium primary meristematic tissue that gives rise to primary vascular tissues During secondary growth the xylem is derived from the vascular cambium Tracheids The principle conducting cells of the xylem are the tracheary elements which there are two types tracheids and vessel elements both of which are elongated cells that have secondary walls and lack protoplasts at maturity and both types may have pits in their walls Long tapering Vessels perforations generally occur on the end walls with the vessel elements joined end to end forming long continuous columns or tubes called vessels Walls are perforated by pits Vessel Elements unlike tracheids vessel elements contain perforations which are areas lacking both primary and secondary walls short wide end walls are open Phloem the principal food conducting tissue in vascular plants Sugars amino acids lipids micronutrients hormones the floral stimulus numerous proteins and RNAs are transported here sieve tube elements the principle
View Full Document
Unlocking...