PHA611 LAB- Microscopy-Plant Diversity PDF

Exercise 8: Roots Fleshy taproots: carrots, beets, radish, turnips Swollen lateral roots: sweet potatoes, ROOTS...

Exercise 8: Roots Fleshy taproots: carrots, beets, radish, turnips Swollen lateral roots: sweet potatoes, ROOTS cassava Three Main Function Fibrous Anchorage - anchors whole plant to soil - For absorption Absorption - (H2O & dissolved - Most are monocot, some dicot nutrients/minerals) - Have many similarly sized root Production of Hormones (cytokinins & - Ex. grass, rice, wheat Gibberellin ○ Cytokinins - responsible for cell division, elongation, and maturation ○ Gibberellin - for opening & closing of stomata (stomates - used for gaseous exchange) ○ Auxin - cell growth and elongation of the plant Roots - Sources of important raw materials for pharmaceutical industry such as drugs, medicines, and starches (ex. Ginseng - Adventitious herbal root) - Ex. Balete, Pandan - Some are edible and are considered as - Does not arise from pre-existing root crops - As the plant age, more root primordial are initiated in the stem tissue ROOT SYSTEM - Increase the absorptive & transport capacities of the root system Tap Root - Most are dicot - Single prominent taproot that is much larger than the rest where numerous lateral roots or branches arise - Ex. raddish (herbaceous tap root) LONGITUDINAL STRUCTURE Root Tip - Region where growth in length occurs Root Cap - Secrete a complex of polysaccharides called “slime or mucigel” - lubricates passage of root through soil - Causes root to release nutrient ion and permits diffusion to roots - “Thimble-shaped” CORPUZ,DELALAMON,PUNZALAN,SALVO,ROMANO,ZINAMPAN 29  - Provides effective protection for apical Found more in monocots & grass roots than meristem in dicots - Gravitropism- Realigns roots growing other than downward Three Primary Meristem Protoderm - gives rise to the epidermis a. Epidermis I. trichomes → secretory (glandular & stinging), non-secretory (scale, branching, stellate, bristle II. guard cells → only dermal cells w/ chloroplast Ground Meristem - Gives rise to ground tissue / cortex a. Parenchyma - uniformly thin b. Collenchyma - evenly thickened; found in corners c. Sclerenchyma - primary wall & secondary wall Procambium - Gives rise to Steele - Stele → central cylinder of the vascular tissue w/ xylem and phloem 2. Zone of Elongation Region when cells expands greatly; cells can be seen Cells begin to differentiate into mature tissues like: ○ Protoderm into epidermis ○ Ground meristem into cortex ○ Procambium into vascular tissues 3. Zone of Maturation Root epidermis Root hairs grows outward; greatly increasing absorption No distinct boundary exist between elongation and maturation Functions to transfer minerals from the epidermis to the vascular bundle onion root tip 1. Zone of Cell Division / Meristem - Protected by thick layer of cell (root cap) - Rapidly dividing cells - Quiescent center → mitotically inactive (G0 Phase) - Activated when the root apical meristem is damaged to produce a new apical meristem Piths – parenchyma tissue from ground meristem CORPUZ,DELALAMON,PUNZALAN,SALVO,ROMANO,ZINAMPAN 30  Cross Section Structure of the Zone of Maturation Stele - vascular cylinder (pericycle, phloem, xylem) 1. Epidermis Outermost layer with root hairs Protostele Siphonostele Lacks cutin to facilitate absorption of water 4 xylem raised circular/ring-like = and minerals (Cutin present in leaves) → triarch,tetrarch, parenchymatous pith Roots Hairs pentarch strands of xylem and Function only for several days, after which phloem surrounding a they die and degenerate parenchymatous pith Absorption of water and minerals is → Polyarch - many increased xylem poles 2. Cortex Transfer minerals from the epidermis to the vascular tissue Endodermis controls movement of water from the cortex toward the stele or vascular cylinder Collenchyma, Parenchyma, Endodermis 3. Vascular Region 3.1 Pericycle Irregular region Found between the vascular tissue and endodermis Region where lateral roots arise 3.2 Phloem Food conducting tissue MONOCOT 3.3 Xylem Water conducting tissue CORPUZ,DELALAMON,PUNZALAN,SALVO,ROMANO,ZINAMPAN 31