Lecture 12 & 13 Land Plants Flashcards
what are general characteristics of modern land plants? (4)
- most live in terrestrial environments
- multicellular, photosynthetic euk
- cell walls made of cellulose
- alternation of generations
what species did land plants have a common ancestor with/evolved from?
- green algae / charophytes
- seen via comparisons of nuclear and chloroplast genes
what are the four key traits that charophytes share with land plants?
- rosette-shaped cellulose synthesizing complexes
- make cellulose microfibrils of the cell wall
- are linear in non-charophycean algae - peroxisome enzymes
- enzymes that prevent the loss of organic compounds during photorespiration - structure of flagellated sperm
- resembles sperm of charophytes, but not all plants’ sperm flagellated - formation of Phragmoplast during cell division
- helps construct cell plate between incipient cells – new cell walls
what are the three possible plant kingdoms?
- viridiplantae: chlorophytes, charophytes, embryophytes
- streptphyta: charophytes and embryophytes
- plantae: embryophytes
what did movement of land plants by charophyte ancestors provide?
- spacious habitats – most niches available
- bright sunlight, unfiltered by H2O or algae
- atm with plentiful CO2
- soils rich in mineral nutrients
- at first, relatively few herbivores or pathogens
what were challenges presented by land?
- scarcity of H2O
- lack of structural support
what are the 4 adaptations that enabled the move to land?
- sporopollenin
- adaptations for water conservation
- lignified vascular tissue for internal transport
- resources became more compartmentalized in terrestrial plants
what is sporopollenin? (2)
- in charophytes a layer of durable polymer prevents exposed zygotes from dying out
- also found in plant spore walls – increases resistance to drying and physical stress
what are the two adaptations for water conservation? (2)
- waxy cuticle: waterproofing, protection from microbial attack
- stomata: gas xchange, water to exit via evaporation, minimize water in dry cond
what does lignin do?
- complex polymer which strengthens and supports plant
what are the two vascular tissues
- xylem: cells carry H2O and minerals - dead walls
- phloem: cells distribute organic products - living cells
what did compartmentalization in plants lead to
- elongation and branching for exposure to environmental resources
what are the five derived traits of plants?
- AoG
- multicellular, dependent embryos – diploid embryo is retained within tissue of female gametophyte
- walled spores in sporangia
- multicellular gametangia
- apical meristems
- additional traits include: cuticle, mycorrhizae, secondary compounds
what is alternation of generations (AoG)?
life cycle of all land plants that alternate between sporophyte and gametophyte generations
what are archegonia and antheridia?
archegonia: female gametangia, produce eggs and are the site of fertilization
antheridia: male gametangia, produce and release sperm
what are apical meristems?
- plant adaptations that sustain continual growth
- contain undifferentiated cells that later differentiate into various tissues
- simple in non-vascular plants, more complex in structures of tips of shoots and roots in vascular plants
what is the cuticle?
waxy covering of epidermis
what are secondary compounds in plants?
adaptations that deter herbivores and parasites
what are land plants informally grouped on?
presence or absence of vascular tissue
what is another name for non-vascular plants?
bryophytes
- not a monophyletic group – relationship to each other and vascular plants is unresolved
what are the two clades of seedless vascular plants?
- paraphyletic
- lycophytes: club mosses and their relatives
- pterophytes: ferns and their relatives
what are the two clades of seed plants?
- gymnosperms
- angiosperms
what are three phyla of bryophytes?
- liverworts - hepatophyta
- hornworts - anthocerophyta
- mosses - bryophytA
what are 6 traits of bryophytes?
- lack true vascular tissue and lack lignin
- most tissues are only one or a few cells thick
- Haploid gametophytes are the most conspicuous, dominant phase of the cycle + Diploid are smaller and entirely dependent on the gametophyte
- often gametophytes are male or female and have separate organs for eggs and sperm: archegonium + antheridium
- 2n zygoes and sporophytes retained and nourished by haploid spores
what does the lack of lignin and vascular tissue do to byrophytes?
- limits their size as there is less H2O storage, strength, nutrient transport
what environment must bryophytes have to reproduce?
must live in wet or aquatic environments that have an H2O film for sperm to fertilize eggs
what is an important ecological role of bryphotyes?
- regulating H2O flow – mosses can lose most body water and rehydrate and reactivate cells when moisture becomes available
- sphagum / peat inhibit bacterial activity
what are 6 traits of extant vascular plants?
- vascular tissue
- complex multicellular roots that anchor vascular plants
- complex multicellular leaves
- sporophylls
- variation in spore sizes among species - most seedless vasc plants are homosporous, all seed plants are heterosporous
- life cycles with dominant sporophytes
what are the dead hollow cells of xylem called?
- tracheids – vascular plants are also called tracheids
what does complex multicellular leaves do for extant vascular plants?
- increase surface area for PS
what are the 2 categories of leaves?
- microphylls: leaves with a single vain; small
- megaphylls: leaves with highly branched vascular system; large
what are sporophylls?
- modified leaves bearing sporangia
what are sporangia?
- spore producing organ
what are sori?
- sori are clusters of sporangia on the undersides of sporphylls
what are strobili?
- conelike structures formed from groups of sporophylls
- ex: lycophytes and most gymnosperms
what is homospory?
- plant that produce one type of spore that develops into a bisexual gametophyte - have both archegonia and antheridia
what is heterospory?
- plants that produce both megaspores: female gametophytes and microspores: male gametophytes
what are five characteristics of seedless vascular plants?
- vascular tissue allowed plants to grow tall
- have flagellated sperm (still needs H20)
- sporophyte dominant form
- gametophytes are tiny independent plants that grow on or below the soil surface
- two phyla: lycophytes & pterophytes
what are lycophytes? (4)
- all are microphyllous and are either homo or heteropsorous
- HAVE strobili
- used to be large trees – now small plants
what are pterophytes?
- includes: ferns, horntails, whisk ferns
- have MEGAPHYLLS
- produce MANY SPORANGIA - SORI – can catapult and carried by wind
- whisk ferns: once “living fossil” – no roots or leaves
- horsetails: carboniferous
- tru ferns: most successful of SVP
