BIO 161 Lecture Notes PDF

12/19/24 Under the appropriate influence, these recent derivatives become differentiated and changed into various types of mature cells and tissues. v parenchymatous cell becomes transformed into another cell type without undergoing an intervening cell...

12/19/24 Under the appropriate influence, these recent derivatives become differentiated and changed into various types of mature cells and tissues. v parenchymatous cell becomes transformed into another cell type without undergoing an intervening cell division---transdifferentiation v when a parenchymatous cell begins to divide and then changes into another cell type---dedifferentiation. 1. During the early stages of embryogenesis, does cell division takes place throughout the young sporophyte? 2. Provide a short explanation (2-3 sentences), how about when the embryo develops, does cell division becomes restricted to opposite ends of the axis, the apical meristems of future root and shoot? 1 2 ❙ DEVELOPMENT OF THE PLANT BODY Development consists of the integrated processes The Body Plan of the Plant Is Established of growth, differentiation, and morphogenesis. during Embryogenesis üGrowth results in increase in size, and during The mature embryo has a limited number of growth, differentiation occurs parts— frequently only a stem-like axis bearing one or more leaf-like appendages - üDifferentiation is the process whereby cells, the cotyledons- hypocotyl. Lower end (the tissues, or organs achieve their distinctive, mature root pole), the hypocotyl bears the incipient root, at its upper end (the shoot pole) the morphological and physiological characteristics incipient shoot. The root may be represented by its meristem during gradual change from their state as single or or by a primordial root, the radicle. groups of meristematic derivatives apical meristem of the shoot located at the shoot pole may or may not have initiated the üMorphogenesis is the achievement of form during development of a shoot. If primordial shoot is present- plumule. development 3 4 § Development consists of the Sachs’s (1875)- classification based on topographic continuity of tissues: integrated processes of growth, vascular plant is composed of three tissue systems- the dermal, the vascular, and the fundamental (or ground). differentiation, and morphogenesis. Dermal tissue system: § Growth- results in increase in Epidermis-primary outer protective covering of the plant body size, and during growth, Periderm- the protective tissue that supplants the epidermis, mainly in plants that undergo a secondary increase in thickness. differentiation occurs. Vascular tissue system contains two kinds of conducting tissues, the phloem § Differentiation is the process (food conduction) and the xylem (water conduction) where cells, tissues, or organs Fundamental tissue system (or ground tissue system: Parenchyma -characteristically living cells, capable of growth and division. achieve their distinctive, mature Collenchyma is a living thick-walled tissue closely related to parenchyma; morphological and physiological Sclerenchyma with thick, hard, often lignified walls—combined into characteristics during gradual coherent masses as tissue or dispersed as individual or as small groups change from their state as single or groups of meristematic derivatives. § Morphogenesis is the achievement of form during development. 5 6 1  12/19/24 TISSUE PATTERNS IN STEMS Meristems and meristematic tissues show varied arrangements of cells resulting from differences in patterns of cell division and enlargement. the cells may divide sluggishly and attain considerable dimensions; may divide frequently and remain small A, periclinal (parallel with the surface). B, radial anticlinal (parallel with the radius). C, transverse (anticlinal division at right angles to the long axis). 7 8 TISSUE PATTERNS IN STEMS Vascular bundle types Stele- Central cylinder composed of primary xylem, primary phloem, and the pith Four widely recognized bundle a. Protostele- the simplest types: form of stele, consists of a solid core of conducting collateral bundle- most common type in which the primary xylem is tissues in which the innermost and primary phloem phloem usually surrounds comprises the outer part; frequent the xylem; common in occurrence in both gymnosperms and primitive seed plants that angiosperms. are now extinct and found bicollateral bundle the primary in whisk ferns, club xylem is bounded both to the inside mosses and other and outside by strands of primary relatives of ferns. phloem (internal and external phloem; b. Siphonosteles- are occur only in some angiosperms. tubular with pith in the two types of concentric center; common in ferns. amphivasal bundles - c. Eusteles-the primary frequent occurrence in some xylem and primary families of monocotyledons and a few dicotyledons, the primary phloem are in discrete xylem surrounds the primary vascular bundles; most phloem. common in present-day flowering plants and amphicribral bundles- common in some ferns, but also conifers found in a few aquatic Types of primary vascular bundles. (a) A collateral bundle of Cassia. Magnification× angiosperms, the primary 120. (b) A bicollateral bundle of Cucurbita (squash). Magnification × 70. (c) An amphivasal bundle of Acorus calamus. Magnification × 157. (d) An amphicribral phloem surrounds the primary bundle in the rhizome of the fern Osmunda. Magnification × 47. xylem. 9 10 Structure and Development of the Plant Body 11 12 2  12/19/24 13 14 15 16 17 18 3  12/19/24 19 20 21 22 23 24 4  12/19/24 25 26 27 28 29 30 5  12/19/24 31 32 33 34 35 36 6  12/19/24 37 38 39 40 41 42 7  12/19/24 43 44 45 46 47 48 8  12/19/24 49 50 51 52 53 54 9  12/19/24 55 56 57 58 59 60 10  12/19/24 61 62 63 64 65 66 11  12/19/24 67 68 69 70 71 12