ANNOUNCEMENTS:Donovan office hours this week in Biological Sciences buildingWed 12:20-1:10 in room 526Fri 2:30-3:20 room 412Learning survey 2 closes today 11:55 pmCase Study 1 session s occur this week. HW assigned 2/7 is due at beginning of class on Wed 2/12Exam 1. Pick up your exams from the BLC, picture ID required. If you think that your answer deserves more points (based on the answer key) please write a written (hardcopy) regrade request that carefully argues your evidence (facts and logic reasoning) for why more points are requested. Please submit your request along with your exam to Dr. Donovan no later than the beginning of class on Mon Feb 17IF UGA closes due to weather this weekLectures and exam 2 will be shiftedThe missed case studies will be made up one week later (same day and time)TODAY: Primary and Secondary GrowthClicker: For plants, meristems allow plants to grow or extend in?A length C neither length not widthB width D both length and widthDicot Plant example (subset of angiosperms)- Primary growth from apical meristems produces short-lived expendable organs with lots of SA for resource acquisition (leaves and roots with hairs) and other structureso Axillary bud meristem (dormant apical meristem)o Root tips (root apical meristemso Shoot tips (shoot apical meristem and young leaves)- Herbaceous plants ONLY have primary growth- Secondary growth from lateral meristems produce “width” growth (increasing circumference) in true woody plants (gymnosperms and angiosperm dicots)o Vascular cambium & cork cambium (lateral meristems)Apical meristems increasing length of plant parts (“reaching” growth)- Assigned reading: Essence of “Plantness”New leaves and stem produced by growth at shoot apical meristemApical meristems on top of developing vascular strand surrounded by leaf primordia (baby leaves where mitotic division have occurred)- As apical meristems grow out in length, the leaves will grow out to full size leavesIf most of the mitotic divisions occur at the apical meristem, then what dominates as leaves expand/grow to full size?A turgor drives cell elongation of flexible cell wallsB leaf apical meristem produces new cells that elongateC Lateral meristem in leaf drives width growthD meiosis produces cells with larger volume- Leaf doesn’t have apical meristem so B is incorrect- No lateral meristem (this occurs on stems to make it wider) so C is incorrect- Meiosis doesn’t happen in any apical meristems so D is incorrect - Elongate cells through turgor pressure because cell walls are flexible so A is CORRECTo Sets up water potential gradient to bring water in to expand wallso Signal to lock down cell wall connections to make cell walls rigid once elongated completelyo No turgor = no growth- Cells doing mitosis are right behind apical meristemsRoot apical meristem- Zone of cell division right around apical meristem- Root cap: Protective layer of cells over apical meristemo First parts are living but some are dead that are just protective- Zone of elongationo In between cell division and differentiation- Zone of differentiation o root hairs formingo no longer moving any moreo movement would rip off root hairsLateral meristems- Lateral branching roots arise from de-differentiated parenchyma near xylem- Root hairs don’t grow into multicellular lateral roots, these are entirely different structure- Root hairs: epidermal cells- Lateral meristems: new apical meristem that grows out; can produce new root hairs- Study question: Why do new roots arise near vascular tissue?Clicker: primary growth from apical meristems produces cells with A primary cell walls C bothB secondary cell walls D neither- Primary cell walls: have to be able to expand- Secondary cell walls: produce all other cell typeso Primary growth produces all tissue types (vascular, epidermal, ground)- Primary & secondary growth very different from primary & secondary cell wallso Cell walls: what cell type is ito Growth: what type of meristem is itSecondary growth- Lateral meristems add girth or thickness- Stems and roots- Woody plants only2 lateral meristems- Vascular cambium: up stem (but not out to leaves) and out to rootsSecondary growth: produced from lateral meristemsSecondary lateral meristems Secondary tissues Function?Vascular cambium  secondary xylem (wood) more transport tissue Secondary phloem (part of bark)Cork cambium  Cork or periderm (part of bark) ProtectionThis year’s growth: reachingPrimary and secondary growth occurring at the same time just different section of plantWhere is the vascular cambium and the tissues it produces?Xylem is on inside of dicotVascular cambium forms between primary xylem and phloemWhere the newest tissue produced by this cambium occur in 2nd year stem?Where is vascular cambium moved to for next year?How does vascular cambium form Secondary vascular tissue/- Cambium: continually displace outwardo Cambial initial (stem cell) divides to form 2 cambial initials, or 1 cambial initial and 1 secondary xylem cell, or 1 cambial initial and secondary phloem cell- More xylem than phloem producedo secondary xylem cells: tracheids, vessel elements, fiberso Secondary phloem cells: sieve0tube elements, companion cells, parenchyma, fibersIn temperate regions- Spring wood xylem: relatively large diameter, thinner wallsClicker: Which wood was most recently produced?A 1 B 2 C 3 D 4Wood = xylem1: secondary phloem2: secondary xylem 3: primary phloem4: primary xylemWhen tree is cut down, vascular cambium is right under bark- All phloem has been pushed off- There is still phloem in a living treeSapwood xylem:- Secondary xylem layers active in water transport- Active in water transportHeartwood xylem:- Older secondary xylem layers- No longer active in water transport- Darker due to resins Dendrochronology: study of tree ring growth pattern- More secondary tissue produced in warm years and less in cool years- Graph showing ring-width for a series of cores taken from preserved Mongolian conifers- Can be used to reconstruct climate, date archeological sites, determine age of oldest living treesWood is xylem (dead sclerenchyma tissue)Secondary dermal tissue- Where is the cork cambium and what tissues does it