BIOL 240W 1st Edition Lecture 6Outline of Last Lecture Outline of Current Lecture Multicellular DevelopmentDeterminate GrowthIndeterminate GrowthMeristemsPrimary Growth in RootsThree Zones of Cell DivisionAnatomyPrimary Growth in ShootsOutline of Current Lecture Soil Bacteria and NitrogenRootsLeavesDermal TissueThree Types of Plant CellsXylem CellsPhloemIndeterminate GrowthCurrent LectureSoil bacteria and nitrogenVery few organisms can use N2 in the atmosphere, and plants need nitrogen. They can only use nitrogen in the form of the ammonium ion to incorporate it into the nitrogen-containing compounds in the plant.Nitrogen-fixing bacteria can take nitrogen gas and fix it into ammonium.Nitrifying bacteria take ammonium as a source of energy and release nitrate and nitrite products.Rhizobium offer usable nitrogen in return for sugars (symbiotic relationship). They set up a vascular system by incorporating themselves into the plant roots to move nitrogen into plant and photosynthates out of the plant for Rhizobium. Rhizobium contain leghemoglobin and a barrier to reduce oxygen exposure to prevent inhibitionof nitrogenase for nitrogen fixation.RootsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Key role in mineral and water uptake.Provide Support (anchorage)Tips of root hairs are the sites for mineral and water uptake.ApexesApical bud is where active growth occurs. It responds to changes in the environment (ex: make bigger leaves, grow taller).Axillary buds remain dormant because of apical dominance. These only become active if they receive a signal.LeavesTo identify a leaf, find the axillary bud.Plants can have different leaflets per leaf depending on axillary budsDermal TissueDermal refers to the outer layer of cells. They contain the waxy cuticle for resistance of water loss.The vascular tissues move water/ minerals (vessels) throughout the plant.Xylem moves water and minerals upward (roots(shoots).Phloem is responsible for sugar transport to other parts of plant that need it.The vascular system comprised of bundles of both xylem and phloem.Three types of plant cellsParenchyma (“typical” plant cell)These cells are classified as ground tissue, photosynthetic, totipotent (undifferentiated), and have no secondary cell wall.CollenchymaTheir main role is support of the plant. They are alive at maturity.SclerenchymaAlso important for support, they are stiff/rigid, and dead at maturity.Types of Xylem cellsTracheids are dead at maturity, contain lignin in secondary cell walls, and are important for water conduction.Vessel elements are dead at maturity.Both types of cells coexist in the xylemPhloemSieve-tube elementsThese cells are alive at maturity, produce energy, and do not have all of the normal, expected organelles.Companion cellsContain complete cells (all organelles present). Each sieve-tube element has a neighboring companion cell.Indeterminate growthPlants grow based on their cues from the environment.MeristemsComprised of undifferentiated tissues (stem cells) that allow plant to have indeterminate growthAllow plants to respond to changes in the environment.Apical meristems are present at the shoot tip. This is where new growth occurs. They exhibit apical dominance over axillary meristems.Axillary meristems and root meristems also presentPrimary growth in rootsA cell division zone is present at the apical meristem.The cell elongation zone increases the length of the plant via elongations of cells, not cell division.The differentiation zone is where cells take their final formThe root cap provides protection for the zones of roots.Vascular BundleThe endodermis is a waterproof strip surrounding vascular tissue in roots.After a taproot is established, the plant grows both above and below ground. Lateral roots establish connections of vascular tissues. A vascular bundle parallels the idea of our capillaries Primary growth of shootsLeaf primordial protects shoot apical meristems.Growth of shoots is due to cell elongation/expansion, not cell divisionLeaf tissues are optimized for photosynthesisAdaxial (upper leaf) is comprised of densely packed palisade mesophyll cells with a high density of chloroplasts for photosynthesis.Abaxial (lower leaf) parts contain the stomata.Guard cells are important because of their regulation of the size of the stomatal pore (regulatinggas exchange and water
View Full Document
Unlocking...