Lecture 11Text Reference:Chapter 24, The Root: Structure and DevelopmentChapter 25, The Shoot: Primary Structure and DevelopmentRoots – FunctionsCan grow around and can get woodier as it grows and kills the tree they are growing on.Anchorage: anchoring the plantAbsorption: absorbing nutrients – water and mineralsStorage: nutrients (sweet potato, sugar beet (root system) – adapted to store sugar and starch)Conduction: by xylem up the root system; they store these for themselves to be able to develop. Take 2 years to reproduce. The second year – it is going to be broken down and the phloem is going to be used up instead of down and around.Reproduction –clonal regeneration. Asexually produced, as a normal option. If there is damage to the parent plant, then the roots can regenerate the entire plant.Synthesis and secretionRoot SystemsPrimary root: most dicots send down the radical becomes the primary root and forms a cap root that goes in deep into the soil to search water.Taproot: can grow to grab water and to keep the roots close together so once it rains it can capture the water more likely.Lateral roots: to increase surface space, grows root hairs which have extremely thin wallsParicama cells: the root cap, the mesophyll also contains these cells, the go to building block for plant anatomy. The root cap is used to protect as it grows downwards.Fibrous rootsAdventitious rootsA lot of dicots send down a primary root in which lateral roots grow. Many monocots choose to grow the fibrous rootsProp Roots: can be found on good many plants, if the plants are tall and thin or can be knocked down easily (like corn). Grow in wet areas and need the extra support. Grow from the prop/side of the plant, once they touch the soil the later root starts to grow and function as normal roots.Examples of root form and growthDepth of Root SystemBoscia albitrunca – 68 meter depth into the soilplant that grows in the dessert,Prosopsis – 53 meters depthmesquite genus; also growing in the dessert area.Tamarix and Acacia – 30 metersjuviniles and can grow into an adult plant. Aracia – in the bean lugene family.Medicago (Alfalfa) – 6 metersLugene familySurface Area CoveredSecale (rye) – 4 months, 639 square metersthe root hairs…Balance Between Roots and ShootsRatio between roots and shoots:unwater can increase the root:shoot ratio; anytime you move plants it is important to not damage the root system.Root Structure – External anatomyRootcap: can constit of living cells, generic permical cells. Protect the tissue above them – which is really important which pushes the roots through the soil.Columella – gravitropism and hydrotropism: the ones that can sense water and sensitive to gravity so it can grow downMucilage sheathRoot hairs: to increase surface area, growing from the epidermisLateral roots: new roots that are forming from the tissue pericycleProcambrium: is going to become xylem and phloremGround: is going to become cortexRoot Structure – longitudinalRootcap: protects apical meristem and etc. so it won’t become more damage then it wouldMucilage: is like a lubricate, so it can slide as it grows; all of these areas that you see; analogous to muscusApical meristem (Zone of cell division): results in growth; dermal cell and ground that’s going to form the cortex. Where mitosis is occurringZone of cell elongation: when plant cells divide, they tend to be a little. square. Many plant cells stretch into becoming a more rectangular shape. Results in grown. Pretty much that’s the point where primary growth stops; anything before that it becomes different cellsMDERZone of maturation (differentiation): cells are maturing, they are taking on specific functions.Root Structure – cross section (dicot)Epidermis: single layer, design to protect because it doesn’t have much of a cell wall. Pretty thin, root tips vulnerable to insects, mammals, etc.Cortex: ground tissue, the cells have a little bit of space between them. Acts like a sponge. Water and minerals can flow easily into the cortex in the root system. Pretty thick;Endodermis – Casparian strips: have between them these strips and it’s part of the cell wall, addition to the cellulose there are a lot of proteins absorb in the strip, this strip makes it preamble to water. Can make water and minerals flow freely. To a large extent can control what can be flowed into the xylem for further transport in the plant body.Pericycle: are the cells that differentiate into the lateral roots (which grows through the endodermis which proceeds to grow into the cycle.)Phloem: located around the xylem. Bringing glucose and nutrients downXylem: dead center in the root, like a cross. Conducts water upIn general, the vascular are in a ring (monocots) that have a pericycle around it which conducts lateral roots and grows fibrous roots, many dicots have central called pifts (ground tissue found in the center and it can be conductive and can also have a storage system, no woody plants)Root Structure – comparison of monocots and dicotsRanunculus (buttercup) – dicotZea mays (corn) – monocotAbsorptive Function of RootsProcess – transport of water and minerals to xylemRole of mycorhizal fungi: allow trees to reach the size they can reach, not the roots because it is not efficient enough to receive water. Parastitic, growing into the root to steal the nutrients, and then it makes it easier for the plant to receive water.Formation of lateral rootsPericycle: the dark blue shows the differeintaionRoot primordium: the stage 2, 2 soon to be lateral rootsModified Roots:Prop rootsStilt roots: extreme exaggerated prop roots. This would help it from not being blown down, etc. extra measure of strength and stability.Pneumatophores: growing in the root forms in the plant forms near and in the water. Help with gas exchangeBanyan Tree: ficus (figs) – a big tropical genus. Often see the banyan growing in a fixed structure. Probably making it inpassable, advantages is support and inpenetrable from other plants to grow and also other animals to come in and nibble on the leavesEpiphytic roots – orchids  grow on the body of other trees, not parasitic. Root systems of majority does not grow into the tree, instead it is photosynthetic and have an extremely thick epidermis, all to prevent water loss.Storage rootBIOL 420 1nd Edition Lecture 11 Text Reference: