Midterm 2 Plant Bio (Molgen 3300)
Midterm 2 Plant Bio (Molgen 3300) 3300
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This 9 page Study Guide was uploaded by Brooke Anderson on Sunday March 8, 2015. The Study Guide belongs to 3300 at Ohio State University taught by Alonso/Hamel in Fall. Since its upload, it has received 323 views. For similar materials see Plant Biology in Biochemistry at Ohio State University.
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Date Created: 03/08/15
Molgen 3300 Plant Biology LECTURE 6 Secondary growth Summary of secondary growth New wood xylem is added outside the old so the wood gets wider New phloem is added inside the old These two tissues are separated by the vascular cambium which gives rise to ray and fusiform initials Heartwood xylem that is no longer conducting darker Sapwood yetconducting xylem tissue lighter Monocots Do not have secondary growth because vascular bundle do not form around a procambium and cannot form a vascular cylinder Therefore no wood Instead their stems enlarge by division of filling parenchyma Note since monocots do not have a meristematic vascular cambium monocots cannot renew their vascular tissue mainly phloem after a damagingly cold winter Therefore tall monocots like palm are only found in climates without winter They have hard leaf bases that make them appear like trees 0 Annuals survive winter without a vascular cambium by producing seeds to survive the winter 0 Herbaceous perennials contain underground growth from which they regenerate the vegetative tissue following winter Molgen 3300 Plant Biology Lecture 7 Leaves Leaf structure is ideal for photosynthesis like a solar panel Large surface area thin amp at towards the sky vacuoles key for large surface area Chloroplasts are most densely located in the leaf cells facing the sky Leaf position minimizes shade no stacking on top of each other 0 Trees are an example of positioning leaves to avoid shading each other Stomata let C02 in while minimizing water loss by being located under the leaf in the shade Leaf veins transport sugars throughout the leaf Leaf tissues from sky to ground Upper epidermis Upper mesophyll the palisade parenchyma column shaped Bundle sheath cells surrounding veins xylem on top phloem on bottom Lower mesophyll the spongy parenchyma irregularly shaped with air between Lower epidermis 0 Include standard pavement cells trichomes and guard cells 0 The guard cells making up stomata are sensitive to temperature amp humiditiy etc LEAF STRUCTURE Between epidermis and middle of leaf are mesophyll cells made up of parenchyma cells with thin primary cell wall and packed with chloroplasts Upper leaf is columnshaped palisade mesophyll with lots of chloroplasts Lower leaf is irregularly shaped spaced out spongey mesophyll for gas distribution Leaf veins transport water and sugars from main vascular system 3 orders primarymajor 9 tertiary big small branched off Phloem on lower side xylem on upper side Bundle sheath cells protect around veins protecting them from air Monocot vs dicot veins 0 Monocots parallel venation ex rice 0 Dicots reticulated venation ex stewartia Leaves in fall change to yellow as chlorophyll degrades any red comes from anthocyanin development in the vacuole Abscission zone forms where the leaf falls off perpendicular to petiole in dicots an abscission zone forms where cells are producing enzymes that weaken their cell wall Meanwhile cells attached to the stem are producing cork for scar tissue leaving a leaf scar so as to protect from pathogens In monocots leaves will remain attached and slowly degrade 9 no abscission zone Sclerophyllous leaves on touch evergreens have schlerenchyma cells under the epidermis with really thick secondary cell wall also have very thick cuticle to be able to overcome winter Modified leaves Bud scales to protect SAM during winter will also leave scars Molgen 3300 Plant Biology Lecture 7 Leaves Bulbs for food storage like onion where layers are leaves protecting apical meristem Some tendrils are leaves if there is an axillary bud above it otherwise modified stem Stipules protect against insects can produce a sticky resin Extra oral nectaries to attract pollinators or ants that will eat other pests Spines Note Thorns are stems spines are leaves like on cacti o Prickles small short outgrowth from epidermis ex rose thorns are prickles Succulent leaves modified for water storage Carnivorous plants that live in lownitrogen environments note leaves still photosynthesize Salt secretory glands in high salt soils perhaps in salt water like mangroves Molgen 3300 Plant Biology LECTURE 9 ROOTS Note in vascular plants only Bryophytes like moss do not have roots Functions Anchor lateral roots very helpful for this Absorption of water and minerals note that desert plants have deepest roots for this Storage of food like in sweet potato or carrot Interactions with beneficial microorganisms mycorrhizae fungus Nfixing bacteria for legumes Origin and development Primary root in embryo is called the radicle and comes from the root apical meristem RAM Recall that the RAM is a site of active cell division for primary growth Lateral roots arise from new RAMs that form from inside the root Two types of root systems 0 Taproot in dicots one main root usually longest amp widest This taproot arises from the radicle primary root and can grow deeper than monocot roots 0 Fibrous roots in monocots all roots are about equal lengthwidth and none come from the embryonic root which decays as fibrous roots form These roots grow wide rather than deep Structure 4 Zones from tip up 1 Root cap protects the RAM from damage The border cells on the edge of root cap produce a complex polysaccharide called mucigel which protects the root cap from drying and being damaged as it punches through the soil These border cells fall off easily they digest their own middle lamella so that they are no longer glued to their neighboring cells because they are faced with much friction and therefore they have a high turnover rate This keeps the root growing The mucigel also helps establish a partnership with bacteria and fungus it creates a diffusion bridge between roots and soil a place where nutrient uptake is facilitated especially in dry soils The root cap is positively gravitropic specialized Gcells or statocytes which are in the columella within the rootcap can sense the direction of gravity and grows toward it hence positive 2 Cell division includes RAM and immediate daughter cells The RAM contains at its center a quiescent zone of low cell division which is there as a safety in case another part of the RAM is damaged 3 Cell elongation where the vascular system starts to form drives the lengthening of the root Molgen 3300 Plant Biology LECTURE 9 ROOTS 4 Cell maturation where root hairs form from the epidermis to take up nutrients by increasing cellular surface area for increased nutrient and water uptake Radial organization of the root from outside to inside 1 Epidermis absorbs water amp nutrients Root hairs which form from epidermal cells are equivalent to leaf trichomes in structure but always called root hairs in roots They function to increase surface are for increased water and nutrient uptake Nutrients pass through the epidermis by apoplastic transport through cell wall From there nutrients ow by symplastic transport through cytosol using protein transporters between cells Cortex mostly parenchyma with many amyloplasts to store starch Endodermis which separates vascular tissue from cortex and contains a waterproofing casparian strip made up of suberin and lignin This strip forces water and the nutrients it carries to enter the endodermis through symplastic routes and prevents passive apoplastic transport of solutes into the pericycle and then the vascular tissues Pericycle separates the vascular tissue from the endodermis A site of intense cell division acts as a meristem when lateral root growth is initiated Vascular tissue primary xylem and phloem that is continuous with the primary vascular system of the stem The xylem and phloem are not in vascular bundles like in the stem but rather side by side with the xylem in the very center in some sort of cross shape and phloem directly outside filling in the space between the cross arms Note 35 make up the vascular cylinder Secondary growth in roots limited in biennial plants which only have 2 seasons none in annuals Secondary growth increases width instead of length and produces wood and cork so the root can survive freezing Vascular cambium forms between xylem and phloem with the secondary phloem to the outside and the secondary xylem to the inside as in stem secondary growth The wood secondary xylem that is generated takes up most of the root Outer bark and inner bark form the same was as in stems forming cork Pericycle part of the bark Lateral roots Originate inside vascular cylinder from the pericycle A new RAM forms within the pericycle which moves out through the endodermis and cortex and then bursts through the epidermis to form a lateral root This new lateral root consists of a root cap an RAM that originated from the pericycle and the same elongation and maturation zones as in primary root growth Adventitious roots form on organs that are not roots like stems and leaves do not arise off of primary root system Therefore monocots have adventitious roots since fibrous roots form after the primary root dies off MODIFIED ROOTS Molgen 3300 Plant Biology LECTURE 9 ROOTS Aerial roots adventitious roots that form from above ground tissues for support Ex prop roots Can act as support for climbing stems 0 Air roots are a type of aerial root that provides oxygen to the plant Ex pneumatophores provide aeration in muddy places like marshes or other soils with low oxygen Note that these roots have negative gravitropism where they grow towards the air for oxygen rather than in the direction of gravity and water 0 Epiphytic orchids grow on top of other plants but not parasitically They have specialized aerial roots that have several layers of epidermis and are green and can photosynthesize Food storage as starch in parenchyma Ex cassava sweet potato Association with microorganisms bacteria or fungi exchange phosphate nitrogen for carbon from the plant
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