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42 Cards in this Set

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Of the RHYNIOPSIDA, ZOSTEROPHYLLOPSIDA, TRIMEROPHYTOPSIDA, PSILOPSIDA & LYCOPSIDA; which are still living?
-PSILOPSIDA
-LYCOPSIDA
What are some defining characteristics to the class PSILOPSIDA?
2 Genera:
-Psilotum
-Tmesipteris

-sporophyte lacks true roots but has underground stems (rhizomes)
-leaves are absent and only enations occur on the photoynthetic stem (Psilotum)
-or leaves are present on the terminal portions of stems (Tmesipteris)
-the vascular system of the stem is protostelic, or can be siphonostelic, such as in older stems of Psilotum, wherein a pith of sclerenchyma occurs internal to the primary xylem
-the primary xylem is exarch and the phloem (composed of sieve cells with lignin in their corners) occupies regions betwen the exarch arms of primary xylem
-sporophyte has synangia, which in are composed of 2 loculi (Tmesipteris) or 3 loculi (Psilotum) fused together in one unit
-spores formed inside each synangium are homosporous and monolete
-shows a resemblance to the earliest land plants
-most primitive of the eisting tracheophytes
Classify PSILOTUM
D- Eukarya
K- Plantae
P- Tracheophyta
C- Psilopsida
O- Psilotales
F- Psilotaceae
G- Psilotum
Classify TMESIPTERIS
D- Eukarya
K- Plantae
P- Tracheophyta
C- Psilopsida
O- Psilotales
F- Psilotaceae
G- Tmesipteris
Discuss the general MORPHOLOGY of PSILOTUM.
-aerial shoots are green
-rhizomes (underground stems) are brown
-aerial shoots can be converted into rhizomes by burying their tips (ie: the 2 shoots are interchangeable)
-both branch dicotomously, terminally and equally
Discuss the 3 types of branching in VASCULAR PLANTS.
1)DICHOTOMOUS
-AKA EQUAL TERMINAL BRANCHING
-resulting branches are equal

2)PSEUDOMONOPODIAL
-AKA UNEQUAL
-successive stronger branches form an apparent main axis with smaller side branches

3)MONOPODIAL
-lateral buds are initiated by the apical meristem which itself continues without subdividing
Discuss the AERIAL SHOOT MORPHOLOGY of PSILOTUM
-are ridged
-bear leafy appendages on some shoots and not on others, particularly the undergound axes or rhizomes (ie: optional feature)
Discuss the UNDERGROUND STEM/RHIMZOME MORPHOLOGY of PSILOTUM
-DO NOT HAVE ROOTS!!!
-rhizomes bear rhizoids (absorbing hairs)
-associated with a fungus (mycorrhizial)
Define MYCORRHIZA
-fungus root
Discuss the GENERAL ANATOMY of PSILOTUM.
-shoot apex is characterized by the presence of a pyramidal apical cell which cuts off daughter cells from 3 cutting faces
-leaves are initiated at the apex as in all other vascular plants, but they stop growing at an early stage and hence remain very small as you have seen
-dichotomizing shoot apex, therefore determinate growth because it can only branch limited amounts of them
Discuss the VASCULAR SYSTEM ANATOMY of PSILOTUM
Rhizome
-protostele form
-also has an endodermis (w Casparian strip) and a pericycle, but may not appear very clearly
-center is usually a core of sclerenchyma which constitutes a pith, thus making this a siphonostele
-primary xylem has the form of radiating arms around the central sclerenchyma
-phloem occurs betwen the arms of xylem
*corners of the sieve cells have some lignified secondary thickenings and so stain pink with phloroglucin
-stele is EXARCH
-leaf traces are ordinarily absent, may find a smal vascular strand may extend from the stele to the vase of the leaf, but not into it.
Descripe the SPORANGIA of PSILOTUM
-3 sporangia are fused in a SYNANIUM
-each synangium terminates a reduced branch and the associated sterile appendages are also borne on that reduced branch
-in the 3 LOCULI of the synangium, many spore mother cells per locule undergo meiosis and produce MONOLETE, HAPLOID SPORES
Describe the GAMETOPHYTE of PSILOTUM
-strongly resembles the rhizome of the sporophyte
-the only difference is that the gametophyte will have microscopic sex organs on it...
-gametophytes are saprophobic and have endophytic fungus
-obviously bears ARCHEGONIA & ANTHERIDIA
Describe REPRODUCTION of PSILOTUM
-the protruding cells of the archegonial neck disintegrate or wither after fertilization, leaving the zygote and then the developing embryo surounded by the benter and the basal most neck cells
-sperms released by the antheridia are multiflagellate and water is required for them to swim to the archegonia
-the EMBRYO developes a distinct foot and a shoot apex
-no evidence of a root
-shoot apex has no leaf primordia early, but will eventually form
-young sporophyte is non photosynthetic until it produces it's first green aerial shoot and therole of the associated fungus in providing the nutrients must be substantial
What are some characteristics of Tmesipteris?
-a pendulous epiphyte with a much branched rhizome and a sparsely branched aerial shoot
-no root
-aerial stems bear consipicuous leaves which are provided with vascular strands (leaf traces)
-leaves have stomata in their epidermis (ie: better developed)
-at the base of the shoot, the appendages are small and scale like
-SYNANGIUM has 2 loculi
What are defining characteristics to the Class Rhyniopsida?
-rootless
-leafless
-dichotomous branching
-terminal sporaniga
-centrarch protosteles
-no living representatives
Classify RHYNIA
D- Eukarya
K- Plantae
P- Tracheophyta
C- Rhyniopsida
O-
F-
G- Rhynia
S- major & gwynne-vaughanii
What are some distinguishing characateristics of Rhynia?
-consisted of underground rhizomes and aerial shoots
-no roots or leaves but the rhizomes bore rhizoids which presumably erved an absorptive function
-aerial shoots branched dichotomously and many of them terminated in single sporangia within which spores can be identified
-centrarch protostele
-very difficult to find gametophytes
-reproduction was thought to be entirely vegetative, and that gametophytes may have developed only rarly in spite of abundant spore production
Discuss the internal stem anatomy of Rhynia.
-epidermis with cuticle and stomata
-cortex consisting of inner and outer zones (the major photosynthetic tissue of the plant body
-simple centrarch protostele consisting of a central core of xylem surrounded by phloem
Classify HORNEOPHYTON
D- Eukarya
K- Plantae
P- Tracheophyta
C- Rhyniopsida
O-
F-
G- Horneophyton
What are some distinguishing characteristics of HORNEOPHYTON?
-like Rhynia, consisted of naked aerial axes which branched dishotomously
-instead of rhizomes, there were corm-like structures without vascular tissue from which the aerial shoot arose
-sporangia were dichotomously branched and contained a central sterile region called a COLUMELLA around and over which the sporogenous tissue developed
What are some distinguishing characteristics of the Class ZOSTEROPHYLLOPSIDA?
-rootless
-have exarch protostelic axes which branched dichotomously (some had pseudomonopodial while other axes were clothed with outgrowths which varied from spine like to leaf like)
-**sporangia were not terminal but rather were produced laterally on the stem on short stalks. They opened by by splitting horizontally into 2 valves
------------------------------
-believed to represent the beginning of the lycopsid line of evolution
-latreal position of the sporangia is considered astep toward the lycopsid condition where sporangia are produced in leaf axils or actually on the adaxial surface of the leaves
-has ENATIONS which become vascularized and eventually gave rise to leaves down the evo chain
Classify ZOSTEROPHYLLUM
D- Eukarya
K- Plantae
P- Tracheophyta
C- Zosterophyllopsida
O-
F-
G- Zosterophyllum
S-
Classify ASTEROXYLON
D- Eukarya
K- Plantae
P- Tracheophyta
C- Zosterophyllopsida
O-
F-
G- Asteroxylon
S-
What are some distinguishing characteristics to the Genus ZOSTEROPHYLLUM?
-lower devonian plant
-thought ot have ben a plant with a tufted growth habit
-grows to a height of about 15 cm
-may have inhabited marshy or aquatic sites
-naked upright axes were somewhat flattened and branched dichotomously
-sporangia on short stalks were laterally placed and were clustered at the ends of upright axes
What are some distinguishing characteristics to the Genus ASTEROXYLON?
-somwhat larger than Rhynia major and its aerial shoots were pseudomonopodial in their branching
-upright axes were densely clothed with small leaf like appendages, but te horizontal rhizomes were naked
-some rhizomes were rather root like in appearance but were not true roots
-vascular system was protostele which was cylindrical in the rhizomes but star shaped with phloem in the bays between the arms of xylem in the aerial axes
-protoxylem was MESARCH (similar to centrarch in that protoxylem occurs in the centre of the surrounding metaxylem, but differs by having several regions of protoxylem instead of just one per stem)
-sporangia on short stalks were placed laterally among the appendages
Define MONOPHYLETIC
-vascular plants which have have a common origin
What are some defining characteristics to the Class TRIMEROPHYTOPSIDA?
-has much in common with the Rhyniopsida (considered to be a direct cerivation from that group)
-best represented by the genus Psilophyton
-Psilophyton was more robust than any of the rhyniophytes, with vertical axes upto 90cm tall arising from horizontal rhizomes
-rootless and leafless, although some spp had spiny enations
-upright axes were strongly pseudomonopodial
-sporangia were terminal in position and occurred in large clusters as a result of repeated dichotomous branching of small fertile branches
-there were also non fertile side branches with dichotomous branching
-vascular system was a robust centrarch protostele
What are some defining characteristics to the Class Lycopsida?
-sporophyte with distinct root, stem and leaves
-leaves are microphylls. They have a trace which is not associated with a laf gap. There is a single, unbranched vascular trace per leaf.
-the vascular system is protosteilc or siphonostelic and may become rather complex. The primary xylem is predomonantly exarch
-sporangia are borne adaxially on leaves (SPOROPHYLLS) or in leaf axils on the stem. There is one sporangium per leaf and it has no direct vascular supply
-lower present numbers (5 genera) presently but lots of them in the Carboniferous pd
-makes the worlds best coal
Classify LYCOPODIUM
D- Eukarya
K- Plantae
P- Tracheophyta
C- Lycopsida
O- Lycopodiales
F- Lycopodiaceae
G- Lycopodium
Discuss the GENERAL MORPHOLOGY of LYCOPODIUM
-herbaceous plants, but show a variety of growth forms and can achieve considerable size
-plants may be upright with a limited development of an underground system, or they may form etensive horizontal axes many feet in length from which upright shoots develop as laterals
-many of the epiphytic tropical spps are pendulous, often with long branching axes haning down from ree branches
-tropical spp may grow as tall as 8 o 9ft
Discuss the LEAF MORPHOLOGY of LYCOPODIUM
-present on all shoots but are almost always small organs
-MICROPHYLLS
-on underground rhizomes, they are reduced to scales
Discuss the SHOOT & ROOT MORPHOLOGY of LYCOPODIUM
-branching of shoot and root is terminal
-true roots are present
-young sporophyte of Lycopodium has a primary root, that is, a root formed in the embryo
-the roots on the adult are not derived from the primary root, but arise from the stem as the plant develops (ADVENTITIOUS)
-such roots are common throughout the vascular plants, including the seed plants
Define ADVENTITIOUS ROOTS
-roots that arise from the stem of a plant
-this term is applied to any roots which do not develope from the primary root or its branches that is/are not part of the primary root system
-such roots are common throughout the vascular plants, including the seed plants
Discuss the GENERAL ANATOMY of LYCOPODIUM
-horizontal and upright stems
-roots
-leaves
-all parts of the plant have the 3 tissue systems
-cortex often has an extensive development of sclerenchyma in it
-endodermis is located at the boundary betwen the corte and the vascular cylinder
-has a pericycle where it should be
Discuss the VASCULAR SYSTEM ANATOMY of LYCOPODIUM
-PROTOSTELE, but may be complex...
-in simplest form, it has a star shaped core of xylem and with phlowm between the radiating arms
-however, the xylem may be separated into plates running parallel to the axis, with phloem extending between themin other cases, the xylem may be separated into a number of irregular strands with phloem among them
-these patterns are considered to be protostelic becuase there is no pith, but they certainly stretch the definition of a protostele
-therefor called a PLECTOSTELE
-stele is EXARCH
Discuss the LEAF ANATOMY of LYCOPODIUM
-microphylls
-are always present even though they may be reduced to scales on the underground axes or rhizomes
-each leaf is supplied with a leaf trace which extends into it as a mid vein
-traces are attached to the periphery of the stele and cause no disturbance or disruption of the central vascular system
Define MICROPHYLL
-leaves whose traces are not associated with leaf gaps
Discuss the SHOOT APEX ANATOMY of LYCOPODIUM
-the apical meristem of this plant does not have an apical cell like that of most of the lower vascular plants including some other lycopsids
-it has a surface layer of somewhat nlarged cells, and underneath this, the diferentiation of tissues begins very quickly
-this surface layer corresponds to the surface layer seen in Psilotum and in a fern
-in this case, a small group of initial cells seems to replace the single apical cell
Discuss the SPOROPHYTE of LYCOPODIUM
-spores are produced in sporangia, which in Lycopsida, are produced in the axils of leaves, or more commonly, on the adaxial surface of leaves (SPOROPHYLL = sporangia bearing leaf)
-TAPETUM is the innermost wall layer of sporangia and provides nutrients for the developing spores
-spores are TRILETE

******************************
Arrangement of Sporangia in Lycopodium:
1) May by found in poorly defined zones along the aerial shoots and closely resemble ordinary vegetative leaves
2) May be grouped terminally in a CONE or STROBILUS, and be smaller than vegetative leaves and otherwise modified
3) The cone may occur at the end of an elongate axis the stalk of which has it's leaves reduced to scales. The sporophylls themselves are usualy modified so that the sporangia are practically enclosed
Discuss the GAMETOPHYTE of LYCOPODIUM
-tough to find
-may require factors like fungus, fire, etc. to encourage germination
-are small, green and surface living
-have a colorless base with rhizoids and an endophytic fungus, and bear green lobes on top with sex organs at their bases
-sex organs are produced in a year or less from germination
-ANTHERIDIA are sunken in the gametophyte and produce large numbers of biflagellate sperm
-vneter of ARCHEGONIUM is also sunken, but the long neck protrudes the surface
-both sex organs form from a single cell
-need free water for fertilization
-embryo has a well developed absorbing foot and a primary root is formed
Discuss the VEGETATIVE PROPAGATION of LYCOPODIUM
-plays a major part in spreading
-in spp with horixontal shoots, the mechanical breaking or dying away of connections allows branches to become new individuals
-pieces of stem which are broken off do root easily and form new plants
-spps which do not have an extensive horizontal system frequently produce special reproductive structures celled BULBILS