Slide 1 Roots Botany LHAP105 A. Shigo Slide 2 Main functions Anchorage & support root systems keep plants upright some plants develop masses of fine, spreading and shallow roots others depend on a few large, woody, flaring roots c1.staticflickr.com A. Shigo wikipedia/commons Slide 3 Main functions Absorption every living plant cell requires water to function water and dissolved minerals are absorbed by roots the healthier the root system, the more extensive the root system, the more potential there is for water and mineral absorption McGraw-Hill Companies, Ltd. Slide 4 Main functions Conduction once water enters the root system, it is moved to the main water transport system, the xylem. water and minerals can then translocate to the stems, leaves, flowers and fruit apbiologywiki.wikispaces.com Slide 5 Main functions Storage Roots cannot make their own energy (no photosynthesis) and depend on the aboveground parts for supply roots contain an abundance of parenchyma cells to allow for storage of energy (in the form of starch) this energy can be used for growth, metabolism, defence, etc. Slide 6 Main functions Hormone synthesis Many different hormones are produced in the roots Cytokinins in particular promote the growth of aboveground shoots. If cytokinins concentrations are low (ie. after transplanting where many roots are lost) there will be little growth of twigs, leaves and buds. www.skyscrapercity.com Slide 7 Root system development when a seed germinates, the first structure that emerges is the primary root called the radicle. Roots that develop from this root are called secondary roots or adventitious roots. There are 2 types of root systems that may develop from a seedling: tap root fibrous roots A. Schill Primary root www.boundless.com Slide 8 Root system development Tap roots tap roots occur when a few of the initial roots enlarge and remain dominant. Other roots that branch from these main roots are much smaller is size Many trees abandon the tap root and develop more wide spreading root systems Pines and oaks however, retain a few large roots with little secondary root development hort.ifas.ufl.edu Slide 9 Root system development Fibrous roots plants with fibrous roots shed the primary root early many roots develop and these branch out to produce more roots resulting in a dense mass Fibrous rooted plants help prevent soil erosion biobook.nerinxhs.org Slide 10 Where do roots grow? roots will grow where there is water, oxygen and organic matter (as do the beneficial microorganisms that help supply the plant with nutrients) oxygen and water and organic matter become more limited as you go deeper into the soil profile tree roots are most often situated in the top 50cm of the soil tree roots will extend well beyond the dripline ISA Slide 11 Root growth and morphology Primary function of roots is to absorb water and minerals roots much continue to grow in length to access enough water to support the expanding aboveground parts The growing root tips consist of 3 regions: cell division cell elongation cell maturation Slide 12 Root growth and morphology Cell Division The region of cell division contains the apical meristem and the root cap the apical meristem will divide and produce cells that will eventually become functional tissues the root cap is made up of gelatinous parenchyma cells that protect the apical meristem as the roots grows into new soil areas lima.osu.edu Slide 13 Root growth and morphology Cell Elongation cells produced by the apical meristem greatly increase in length and widen a bit and begin to differentiate into functional tissue This pushes the the root tip forward these elongated cells remain in the same place, stationary for the rest of the plant’s life en.wikipedia cell elongation Slide 14 Root growth and morphology Cell Maturation cells finish their differentiation and become functional tissues root hairs develop in this region to increase the surface area for absorption of water and minerals the cuticle is very thin on roots, nonexistent on root hairs Slide 15 Root anatomy there are 3 tissues in roots that do not exist in any other plant organ: root cap endodermis & casparian strip pericycle Slide 16 Root structures root cap as previously mentioned, the root cap ‘protects’ the apical meristem the cells in the root cap are lubricated, ‘gelatinous’, to allow to root to develop into the soil spaces the cells are continually damaged, torn but then replaced the root cap can also ‘sense’ gravity root cap lima.osu.edu Slide 17 Root anatomy the endodermis is a single layer of cells with cell walls that are cemented together by suberin layers called the ‘casparian strips’ this membrane is selectively permeable it regulates water and dissolved substances that entered the root and now want to get into the xylem Slide 18 Root anatomy when you see the root hairs, you know that the cells in this region have differentiated into functional tissue the whole central cylinder of the root is called the stele the pericycle develops lateral roots (from just inside the stele) Slide 19 The root environment Water primary function of roots is to absorb water Oxygen for respiration, to provide energy for metabolism Temperature (around 10℃) cooler than other plant organs Microbial activity en.wikipedia en.wikipedia en.wikipedia en.wikipedia Slide 20 Uptake of water and minerals First, water and dissolved minerals are taken into the root through diffusion and osmosis. Water can move freely through the endodermis with no energy required. dissolved minerals however require energy to pull these through. This process is called active transport. Slide 21 Specialized roots mycorrhizae (fungus-root) most plants associate with beneficial fungi to develop a brutally beneficial association the fungi attaches to the root, and because of their masses of hyphae they can improve the plants ability to absorb water and nutrients. in return the plant provides the mycorrhizae with food (sugars and amino acids) A. Shigo Slide 22 Specialized roots Bacterial nodules Plants in the legume family as well as Alders and Birch can fix nitrogen from the atmosphere (N2) and convert it to a plant use form, nitrate (NO3) the bacteria "infect" the root and a nodule forms. The bacteria receive sugars from the plant in return for “fixing” the nitrogen for their host Symbiotic bacteria include the genus Rhizobium for pea family plants and Frankia for others en.wikipedia.org Slide 23 Specialized roots Storage roots Dandelions and carrots are examples of roots that accumulate and store energy in the form of carbohydrates en.wikipedia.org Slide 24 Specialized roots Adventitious roots these are roots that arise where you would not expect them take a cutting from a house plant, put it in water or media, and roots may form to give you a new plant! plantsarethestrangestpeople.blogspot.com Slide 25 en.wikipedia.org en.wikipedia.org Specialized roots Propagative roots tuberous roots are used as a form of vegetative reproduction eg. dahlias, sweet potatoes root tubers can be distinguished from stem tubers (ie. regular potatoes) as root tubers do not have buds or “eyes” Sweet potatoes Slide 26 Specialized roots Aerial roots prop roots corn plants produce prop roots to help support the plant climbing roots some jungle plants can hoist themselves up towards sunlight by developing climbing roots answers.yahoo.com unusualplaces.org Slide 27 Why are there no roots on the creek side of this spruce?