2005 BOTANY Chapter 4A&B Root & Leaves PDF

Dr.Mohamed Elshebly 20005 BOTANY CHAPTER 4 A,B ROOT & LEAVES 1 ‫محمد الشبلي‬.‫ د‬0925121809  Dr.Mohamed Elshebly ‫محمد‬.‫د‬ ‫الشبلي‬...

Dr.Mohamed Elshebly 20005 BOTANY CHAPTER 4 A,B ROOT & LEAVES 1 ‫محمد الشبلي‬.‫ د‬0925121809  Dr.Mohamed Elshebly ‫محمد‬.‫د‬ ‫الشبلي‬ Root Root : its the axial organ of plant with geotropic growth.  Many “primitive” plants (all mosses & even some ferns like Psilotum) do not have roots.  However, large homoiohydric plants need the constant supply of water & minerals, & this evolutionary challenge was responded with appearance of the root system. Root :. Functions of the roots : 1. Anchorage of plant in soil. 2. Water & mineral absorption & transport 3. Food storage & communication with other plants. There are different types of roots: I) Primary root originate from seedling. II) Secondary (lateral) roots originate from the primary roots. III) Adventitious roots originate on stems (sometimes also on leaves), EX... are prop roots of screw pine (Pandanus). There are two types of root systems. 1. Fibrous root system : multiple big roots that branch & form a dense mass, which does not have a visible primary root (“grass-like”). 2 ‫محمد الشبلي‬.‫ د‬0925121809  Dr.Mohamed Elshebly 2. Tap root system, one main root that has branching into lateral roots (“carrot-like”). TISSUES OF THE ROOTS A -- Non Vascular tissues : 1 -- Epidermis :  Root hair : Lateral protrusions of epidermal cells which active in water , mineral & nutrient uptake. 2 -- Cortex :  Cortex basically made up of parenchyma cells.  In conifers & dicots with secondary growth the cortex is shed.  In monocots ( without secondary growth ) retain their cortex & many develop sclerenchyma tissue.  Amyloplasts : store Food ( mostly starch ) in corex.  chloroplasts develop if the root is exposed to light. 3 -- Endodermis :  Its The inner most layer of the cortex the encircles the vascular tissue.  Along the walls of endodermal cells is a suberin-rich fatty layer called the casparian strip.. 3 ‫محمد الشبلي‬.‫ د‬0925121809  Dr.Mohamed Elshebly  It blocks absorbed water from passing between the cells to the xylem; thus, water must pass through the selectively permeable membranes of endodermis cells instead ,( an effective filtering system.)  Vascular tissue : 1-- Pericycle : Is a thin walled parenchyma surround the vascular tissue.  Is site of formation vascular cambium & lateral roots. 2– Xylem :  If no Xylem is formed in the center of the root , parenchyma tissue develped there.  Primary xylem arms radiate from the center & vary in number.  In Dicots include Diarch (2 arms ) , Triarch ( 3 arms ) or Tetrach ( 4 arms) & in monocot type is polyarch ( many arms) 3 – Phloem :  Procambium cells, between the radiating arms of primary xylem, produce primary phloem outward and xylem tissue inward.  In secondary growth, the vascular cambium, extends completely around the tips of the xylem arms and inside the primary phloem poles. It produces secondary xylem inward and secondary phloem outward. Root types : 1. Radicle: primary root In conifers & dicots. 2. Seminal: In monocots the first formed roots , which eventually die & replaced by adventitious roots emerge from the stem. NOTE: Dicots may also have accessory adventitious roots, for example, the aerial roots on vines such as ivy. ROOT MODIFICATIONS : 1 – Storage roots : 4 ‫محمد الشبلي‬.‫ د‬0925121809  Dr.Mohamed Elshebly  Its thickenned roots such as carrot , beet , sweet potato , manroot , begonia & dahlia.  for food storage & are seen in many bienninals & perennialis Biennial plant : is one that produce leaves the first year & flowers & fruit the second year & then die.  Perennial plant : lives for more than two years. 2 – Prop Roots :  Some plants develop supporting roots as found in corn (zea) & mangrove (Rhizophora ). 3 – Contractile or shortening root : M Help pull & anchor the plant more firmly in the soil. M common in herbaceous dicots & monocots , present in tap root , adventitious root , lateral roots & roots of under ground storage stem such as corms & bulbs. NOTE : Herbaceous plant or herb : is nonwoody & can die to the ground in freezing climates. Symbiotic Relashinships in roots : A -- Nodules involved in Nitrogen fixation : M Some plants are stimulated by certain bacteria to develop extra tissues in the roots in the forms of nodules. M Where (N2) in the air is fixed that is converted to amonia (NH3) mainly , which converted to organic forms such as amino acid. 5 ‫محمد الشبلي‬.‫ د‬0925121809  Dr.Mohamed Elshebly M E.g found in alfalfa (Medicago sativa) , clover (Trifolium ) , garden pea (Pisumsativum ) & garden bean ( phaseolus vulgaris). B -- Mycorrhizae :  Between fungi & root ( mutually beneficial)  fungi increase the uptake of minerals, particularly P & water.  Root cells provide sugars, amino acids, vitamins & water. GOOD LUCK FOR ALL Dr.Mohammed Elshebly B --- LEAF leaf (foliage) : is lateral photosynthetic organ of shoot with restricted growth.  Features: not grwoing by apex , not producing new leaves. having bud in axil , having hierarchal morphology & anatomy  The connections between blade & stem through the petiole  Blade - the flat, expanded portion of the leaf.  Its functions are photosynthesis , respiration , transpiration & synthsis of secondary chemicals. 6 ‫محمد الشبلي‬.‫ د‬0925121809  Dr.Mohamed Elshebly Anatomy of the Leaf: o 1. Epidermis with stomata, 2 mesophyll (kind of parenchyma). 3. vascular bundles, or veins. o The mesophyllhas palisade & spongy : - Palisade is located in the upper layer & Act as 1 - Decrease the intensity of sunlight for the spongy mesophyll. 2 -- Catches slanted sun rays. The palisade consists of ( long, thin, tightly arranged cells with chloroplasts along sides). The spongy cells are roughly packed, they are rounded & have multiple chloroplasts ). DICOT LEAF MONOCOT EPIDERMAL one or more layers with cutin have bulliform cells. TISSUE (waterproof). The bubble-shaped, water- Stomata of guard cells are filled control leaf rolling present on the upper & lower (when the leaf is dry) & surface or only on the lower unrolling (when the leaf is surface. turgid or filled with water). Hairs & glands may also be present GROUND The parenchyma are divided into consists of only spongy TISSUE A -- palisade : columnar cells & which contain chloroplasts 7 ‫محمد الشبلي‬.‫ د‬0925121809  Dr.Mohamed Elshebly lie under the upper epidermis &. contain most of the chloroplasts B -- The spongy: has irregular- shaped with air spaces between & lies above the lower epidermis. VASCULAR  A leaf vein usually has xylem  Grass leaves have TISSUE on the upper & phloem on the bundle sheaths lower. surrounding each vein.  A layer of parenchyma Sclerenchyma fiber Strands cells called a bundle sheath , may be associated with the which functions in moving veins. materials between the vein & the mesophyll tissue, usually encloses small veins. o Venation : The arrangement of veins& veinlets in leaves (Lamina) Reticulate : It is found in dicots. Parallel : It is found in monocots. Blade Types: 1 -- Conifer: The leaves of conifers are needle-like as on pines or scale-like as on junipers. M ( evergreen , single vein ) 8 ‫محمد الشبلي‬.‫ د‬0925121809  Dr.Mohamed Elshebly 2--Dicot: Most have pinnate (feather-like) venation in which major veins diverge from one large mid-vein.. Some have palmate (hand-like) venation. 3 -- Ginkgo, this unique plant has fan-shaped leaf blades with dichotomous venation. The leaves are deciduous & shed within a 24-hour period. 4 -- Monocot: have narrow strap-shaped. with parallel venation, Leaf Attachment: Petiolate: The leaf blade is attached to stem by petiole. Sessile: When the blade is attached directly to the stem without a petiole,. Leaf Form: Simple: has one blade, which may be broad ,narrow, or needle like Compound: is one that has two or more blade-like leaftlets. 9 ‫محمد الشبلي‬.‫ د‬0925121809  Dr.Mohamed Elshebly Leaf Arrangement: Opposite: Two leaves emerge opposite each other at the same node. Alternate:, single leaves are attached spirally at different nodes. Whorled: several leaves emerge together around the same stem node. o Duration of leaf: Cauducuous (Fagacious) : Falling off soon after formation. Ex: Opuntia, Cissus quadrangularis. Deciduous: Falling at the end of growing season so that the plant is leafless in winter/summer season. Ex: Maple, Plumeria, Launea, Erythrina. Evergreen: Leaves persist throughout the year, falling regularly so that tree is never leafless. Ex: Mimusops, Calophyllum. Marcescent Leaves not falling but withering on the plant ( Fagaceae ). Leaf Modifications: 1 -- Bract : Associated with a flower, bracts are reduced or modified leaves. 10 ‫محمد الشبلي‬.‫ د‬0925121809  Dr.Mohamed Elshebly 2 -- Carnivorous Leaves: live in low nitrogen environments & enzymatically digest animals (mainly insects) in their leaves to supplement nutritional needs. 3 -- Phyllode: This is a widened petiole that appears bladelike.  In the acacia plant, some leaves consist of only petioles (phyllodes). 4 -- Spine: highly reduced leaves or stipules found on many herbs, shrubs, & trees. 5 -- Stipule: Usually in pairs, stipules are basal appendages to the petiole. They may appear as hairs, leaves, tendrils, or spines. 6 -- Succulent Leaves : An adaptation to dry environments, some plants store water in mesophyll M The epidermis may have thick cutinized & lignified walls to reduce water loss. M In some succulents, the stomata reverse the usual condition & open only at night.  ‫قيل لنابليون بونابرت يوما ان جبال الالب شاهقة‬ ‫تمنع تقدمك‬  ‫فقال يجب ان تزول من الأرض‬ Good Luck My Doctors ,,,,, Dr.Mohamed ElsheblY 11 ‫محمد الشبلي‬.‫ د‬0925121809