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34 Cards in this Set

  • Front
  • Back
What is the PROMERISTEM?
-the Shoot Apical Meristem (SAM)
-can be dome shaped, flat or depressed
What is the SHOOT APEX?
-the Shoot Apical Meristem (SAM) + leaf primordia
-cells divide at a right angle to the reference surface
-the result is like stretching an elastic (sideways growth)
-cells divide parallel to the reference surface
-the result is a like adding lego blocks on top of eachother (fattening/thickening)
What are the 2 regions found in the PROMERISTEM?
-cells form in the anticlinal plane

-cells form in the anticlinal and periclinal plane
-plants that produce seeds without an ovary
What is different about the promeristem in gymnosperms?
-has a central zone of rather large cells which seem to divide infrequently
-this central zone is easily recognized in prepared longitudinal sections because it stains lightly
-possible that a central group of cells that do not divide very often may be of fundamental importance, perhaps more so than the tunica and corpus. It could be involved in the mechanism which keeps the promeristem permanently meristematic. Possibly cells which divide at a rapid rate cannot keep this up indefinitely and must be replenished from time to time from a region where division is less active
What is different about the promeristem in lower vascular plants? (ie: ferns and horsetail)
-they have a surface layer of large and elongated cells which divide both antilinally and periclinally
-usually in the centre of this layer, there is a pyramid shaped apical cell
-this cell divides very regularly and is regarded as the INITIAL CELL/APICAL INITIAL
-it doesn't seem to divide very often and is thought to perform the same role as the central zone of cells in gymnosperms and angiosperms
How do lateral branches develope?
-develop from buds in the axils of leaves
-the origin of these buds is from the promeristem of the main shoot
-as a leaf primordium is formed, a small portion of the promeristem is left behind without differentiatino just above the primoridum
-below the region of the meristem this detached portion becomes the apical meristem of a lateral shoot
-it forms a bud which may not expand for some time
-the area where differentiation begins
-found just behind the promeristem
What are the 3 immature tissue systems and what do they develope into?


3)Ground Meristem
-Ground system
How does the vascular system develope?
-the initial differentiation of provascular tissue at the base of the promeristem can be seen to occur simulataneously in stem and leaf primorida
-this is imoprtant because it helps to explain the complete integration of leaf and stem vascular systems in the mature shoot
-early in the differentiation of vascular tissues, the cells axquire an elongate shape and this becomes more distinct as you proceed basally from the promeristem
-when differentiating vascular cells have become recognizable elongated, they are referred to as PROCAMBIUM
What is the ROOT CAP?
-protection for the Root Apical Meristem
-constently being sloughed off and replaced
-therefore the RAM not only produces cells behind it, but in front of it as well
-common in roots
-when the vascular material is smack dab in the center
What is the purpose of the PERICYCLE?
-the tisue that give rise to lateral root primordia
-a primordium begins as a localized centre of cell division activity usually located opposite one of the xylem arms
-this then becomes organized into a root apex which, as it forms a new root, pushes throught the surrounding tissues and emerges from the surface
-this method of branch formation, called ENDOGENOUS, contrasts sharply with the formation of lateral branches of the shoot
What is the STELE?
-a term applied to the central vascular column of a stem or root however much it may be fragmented or dissected
List 4 types of STELES discussed in the manual.
-the simplest
-consists of a central core of xylem with phloem around it

-instead of a solid core of xylem, there is a tube of xylem surrounding a central pith
-pith is considered part of the stele

-arranged, fragmented bundles

-random vascular bundles
What is EXARCH?
-refers to the differentiation of OUTSIDE of procambium first
-therefore OLD xylem is outside
-refers to the differentiation of INSIDE of procambium first
-therefore OLD xylem is INSIDE
-the stage between the zygote and the young plant stage
-occurs inside the developing sed
-bipolarity is already well established in the embryo of the flowering plants, with a shoot apex at one end and a root apex at the other
-can distinctively see COTYLEDONS
-arise early in emryology, at about the time that the shoot apical meristem is set off
-unlike other leaves in the plant, they are not initiated by the apical meristem
-if they are filled with stored nutrients, the may not even look very leaflike
-in the seeds of grasses such as corn, the single cotyledon is a flat, shield like structure called the SCUTELLUM and the rest of the embryo is embeddied in it's outer face
What is an ENDOSPERM?
-a nutritive tissue that covers the embryo in some spp
-absorbed by the embryo and it's nutrients largely stored in the cotyledons
-the axis or stem of the embryo or seedling betwen the coyledons and the top of the primary root
-if it elongates in germination, the cotyledons are carrie above the ground
-if it doesn't, the cotyledons remain below ground
-the shoot apex of a fully developed embryo which includes several leaf primordia or may consist of little more than the apical meristem
-the primordial root
-term used for grass embryos
-the first leaf beyond the cotyledon or scutellum
-tubular structure
-term used for grass embryos
-the internode between the cotyledon and the coleoptile
-may or may not elongate
-term used for grass embryos
-a sheath like structure that covers the radicle
-a body(mass of tissues) imposed on the primary body
-increase in girth
-not a complete plant, though it often makes up the bulk of a plant as is the case in any dicot tree
-comprises only certain tissues; secifically it augments or supplements the vascular and the dermal systems only
-it is produced by SECONDARY or LATERAL MERISTEMS, the VASCULAR CAMBIUM(secondary vascular tissues) and the CORK CAMBIUM(secondary dermal tissues)
How does the VASCULAR CAMBIUM form?
-originates in the bundles
-between the bundles, there is no procambium, only parenchyma
-after cambial activity has begun in the bundles, an influence at least partly chemical in nature (growth substances) sems to spread out from this toward adjacent bundles, causing parenchyma cells between the bundles to begin dividing in the same way
-what has happened is that the cells that were already there have now become meristematic
-there are some anticlinal divisions aswell so that the cambium keeps up with vertical growth
What is the main difference between primary and secondary vascular tissues?
-the secondary are more massive and the cells tend to be arranged in radial rows, related to the initial cells in the cambium which produced them
-secondary tissues ahve rays in them too
What are the 2 types of cells in the cambium? (seen in tangential longitudinal)
1)Fusiform Initials
-long and tapered and are much wider laterally than they are in the radial dimension
-give rise to the elongate conducting and supporting cells of the secondary xylem and phloem as well as to the parenchyma which is not in the rays

2)Ray Initials
-responsible for the rays which extend across the secondary xylem and phloem
What is the CORK CAMBIUM
-replaces dermal tissue system
-arises under the epidermis, usually somewhere in the coritical region, from cells that already have differentiated
-produces layers of protective cork towards the outside of the stem
-cork cambium does not continue to function over long periods of time, it is replaced by new layers which arise underneath it, again from parenchyma cells in the cortex
-of course as soon as a new layer of impervious cork is formed, everything external to it dies including the previous cork cambium
What is BARK?
-everything external the vascular cambium