Heterotrophic Plants Lecture Notes BIO203 PDF

11/11/24 BIO203: Intro to Plant Morphology and Physiology Guest lecture: Heterotrophic Plants Saša Stefanović – Biology at UTM 1 External links and resources Two major sources of information on parasitic plants (as well as credits for photographs):...

11/11/24 BIO203: Intro to Plant Morphology and Physiology Guest lecture: Heterotrophic Plants Saša Stefanović – Biology at UTM 1 External links and resources Two major sources of information on parasitic plants (as well as credits for photographs): 1) The Parasitic Plants Connection website http://www.parasiticplants.siu.edu/ Dr. Dan Nickrent 2) Digital Atlas of Cuscuta https://www.wlu.ca/page.php?grp_id=2147&p=8968 Dr. Mihai Costea 2 1  11/11/24 Green plants - Diversity 3 Green plants - Primary production Carbon dioxide + water + energy = sugar + oxygen (~105 Gt of carbon fixed per year) 4 2  11/11/24 Green plants - Adaptations for photosynthesis Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 5 Trophic conditions Two major trophic conditions in plants: Autotrophic - able to synthesize the nutritive substances it requires from inorganic substances in its environment [from Greek: autos - self; trophos - feeder] Heterotrophic - only partially able or completely unable to synthesize the nutritive substances it requires from inorganic substances in its environment [from Greek: heteros - other; trophos - feeder] Loosely referred to as Þ parasitic 6 3  11/11/24 Heterotrophe - definition “An organism that grows, feeds, and is sheltered on or in a different organism while contributing nothing to the survival of the host” This definition excludes benefical (mutualist) relationships like plant/mycorrhizal interactions or plant/bacterial symbiosis Not to be mixed with epiphytic plants! Epiphytes grow upon other organisms but do not depend on them directly for nutrients [from Greek: epi - upon; phyton - plant] Examples: Þ 7 Epiphytic plants (≠ heterotrophic plants) orchids aroids ferns bromeliads 8 4  11/11/24 Noxious epiphytes (≠ heterotrophic plants) Kudzu vine (Pueraria) Ivy (Hedera) 9 Types of heterotrophic plants Two major groups of heterotrophic plants: I. Parasites - true parasitic plants, attached to a host through a specialized organ called haustorium (pl. haustoria) Haustorium - a sucker-like swelling on a root or stem which invades a host and makes direct physical connection of vascular tissue between the parasite and the host II. Mycotrophs - parasites on fungi [from Greek: mykes - fungus; trophos - feeder] A ‘manage-à-trois’ involving the heterotroph, the fungus, and the autotroph, which is the ultimate source of nutrients Before the involvement of mycorrhyzal connections was recognized, these plants used to be called saprophytes [from Greek: sapros - rotten; phyton - plant] 10 5  11/11/24 Haustoria Q: what makes a plant a parasite? A: the presence of a haustorium! 11 Haustorial development 12 6  11/11/24 I. Types of parasitic plants Different ways to subdivide parasitic plants given the degree of their dependence on the host and type of connection to the host: Holoparasitic - get all or almost all of their nutrition and water from their hosts; unable to photosynthesize; lack of chlorophyll [from Greek: holo - entire] Hemiparasitis - get either only water or water plus some nutrient supplementation (but not all of it) from their hosts; able to photosynthesize with ± efficiency; contain at least some chlorophyll [from Greek: hemi - half] Obligate parasites - must attach to a host to complete its life cycle (includes all holo- and some hemi-parasites) Facultative parasites - does not require a host to complete its life cycle (includes some hemi-parasites) Branch parasites - grows completely above ground and attaches to the branches/stems of host(s) Root parasites - grows completely or partially underground and attaches to the roots of host(s) 13 Phoradendron Comandra Loranthus Cassytha Pedicularis Bellardia Striga Castilleja 14 7  11/11/24 Prosopanche Hydnora 15 Rafflesia Rhizanthes Sapria 16 8  11/11/24 Mitrastema Pilostyles Pholisma Cynomorium 17 Cuscuta 18 9  11/11/24 Conopholis Epifagus Eremitilla Boschniakia Harveya Orobanche 19 II. Types of mycotrophic plants Mycotrophes do not have haustoria! Instead, they somehow, through plant hormone-like compounds, encourage fungi to connect with them; then, they ’turn tables’ and actually obtain nutrients out of the fungi Mycotrophs tend to occur in groups of plants that already have a close relationships with fungi (i.e., mycorrhizal associations) Monotropa uniflora 20 10  11/11/24 Ericaceae Pyrola Moneses Monotropa Hypopitys Sarcodes Pleuricospora 21 Gentianaceae Obolaria Bartonia Voyria Orchidaceae Neottia Coralorrhiza Rhizanthella 22 11  11/11/24 Parasitaxus - the only heterotrophic gymnosperm 23 Asterales Apiales Origins of heterotrophic plants Dipsacales Aquifoliales Lennoaceae Lamiaes Orobanchaceae Gentianales Gentianaceae Solanales Convolvulaceae Asterids Garryales Boraginales Diapensiaceae Heterotrophy evolved ~25-30 Ericales Cornales Ericaceae Mitrastemonaceae times independently in seed plants Malvales Rafflesiales Sapindales Apodanthaceae Cytinaceae Brassicales Rafflesiaceae Fagales Cucurbitales - In some cases, relatively recently: Fabales Rosales 10-20 Mya Celastrales Oxalidales - In some cases, quite old: Malpighiales Rosids Zygophyllales 100-150 Mya Geraniales Krameriaceae Myrtales - Some may be becoming Crossomatales EUDICOTS Cymonoriales heterotrophs as we speak… Saxifragales Cynomoriaceae Balanophorales Balanophoraceae Santanales Viscaceae Caryophyllales Santalaceae Berberidopsidales Opiliaceae Gunnerales Loranthaceae Proteales Misodendraceae Olacaceae Ranunculales ANGIOSPERMS Ceratophyllales Piperales Hydnoraceae Winterales Laurales Lauraceae Magnoliales MONOCOTS Orchidaceae ITA Triuridaceae Nymphaeales Burmanniaceae true (haustorial) parasites Amborella Gnetales parasites on fungi - mycotrophes GYMNOSPERMS Coniferales Podocarpaceae Ginkgoales Cycadales 24 12  11/11/24 Evolution of heterotrophy - hypotheses Two major hypotheses on how plants switch from autotrophy to heterotrophy: Evolutionary Transition Series hypothesis - gradual change from autotrophs to holoparasites via facultative and obligate hemiparasites; “down the slippery slope”; would involve a large number of small changes Punctuated Equilibrium hypothesis - sudden shifts from steady states; would predominantly involve a limited number of key mutations of large effect Empirical data are equivocal at present… Some evidence available in support of both alternatives 25 Phylogenetic predictions from competing hypotheses Evolutionary Transition Series Punctuated Equilibrium (ETS) hypothesis hypothesis auto- hemi- holo- auto- hetero- hetero- e.g., Cuscuta, myotrophyc e.g., Orobanchaceae, Ericaceae, etc… Orchidaceae 26 13  11/11/24 Phylogenetic data equivocal Cuscuta Orobanchaceae Cuscuta pentagona Cuscuta sandwichiana Cuscuta gronovii Cuscuta sp. Cuscuta europaea Cuscuta japonica Cuscuta reflexa 27 Parasitic Reduction Syndrome The suite of changes includes: Loss of leaves (reduced to scales) Overall smaller vegetative size (no need for branches to hold leaves) Loss of roots (reduced to short stumpy projections with haustoria) Loss of chlorophyll Loss of genes needed for photosynthesis Fast rates of gene evolution in genes that are present An evolutionary maxim “Use it or lose it!” applies here well, both at morphological and molecular levels [interestingly, the reproductive structures (flowers) remain and are frequently quite prominent Þ can’t get away from the need to cross-pollinate] This combination of traits is repeated in many different groups of parasitic plants - independently evolved similarities due to similar selection pressures Þ rampant convergent evolution 28 14  11/11/24 Convergence “Textbook” examples of independently evolved similarities due to convergent evolution (analogy) and not to recent common ancestry (homology) 29 Convergence Asterales Apiales Dipsacales Aquifoliales Lamiaes Gentianales Solanales Asterids Garryales Boraginales Ericales Cornales Malvales Rafflesiales Sapindales Brassicales Fagales Cucurbitales Fabales Rosales Celastrales Oxalidales Cuscuta Malpighiales Rosids Zygophyllales Geraniales Myrtales Crossomatales EUDICOTS Cymonoriales Saxifragales Balanophorales Santanales Caryophyllales Berberidopsidales Gunnerales Proteales Ranunculales ANGIOSPERMS Ceratophyllales Piperales Winterales Laurales Magnoliales MONOCOTS ITA Nymphaeales Amborella Gnetales GYMNOSPERMS Coniferales Ginkgoales Cycadales Cassytha 30 15  11/11/24 Convergence Asterales Apiales Dipsacales Aquifoliales Lamiaes Gentianales Solanales Asterids Garryales Boraginales Ericales Cornales Malvales Rafflesiales Sapindales Brassicales Fagales Cucurbitales Fabales Rosales Celastrales Boschniakia Oxalidales Malpighiales Rosids Zygophyllales Geraniales Myrtales Crossomatales EUDICOTS Cymonoriales Saxifragales Balanophorales Santanales Caryophyllales Berberidopsidales Gunnerales Proteales Ranunculales ANGIOSPERMS Ceratophyllales Piperales Winterales Laurales Magnoliales MONOCOTS ITA Nymphaeales Amborella Gnetales GYMNOSPERMS Coniferales Ginkgoales Cycadales Cynomorium 31 Convergence Asterales Apiales Dipsacales Aquifoliales Lamiaes Gentianales Solanales Asterids Garryales Boraginales Ericales Cornales Malvales Rafflesiales Sapindales Brassicales Fagales Cucurbitales Fabales Rosales Celastrales Conopholis Oxalidales Malpighiales Rosids Zygophyllales Geraniales Myrtales Crossomatales EUDICOTS Cymonoriales Saxifragales Balanophorales Santanales Caryophyllales Berberidopsidales Gunnerales Proteales Ranunculales ANGIOSPERMS Ceratophyllales Piperales Winterales Laurales Magnoliales MONOCOTS ITA Nymphaeales Amborella GYMNOSPERMS Gnetales Coniferales Hypopitys Ginkgoales Cycadales 32 16  11/11/24 Plastid genome losses/reductions ? Ipomoea (outermost; 162 kbp) - autotrophic Cuscuta 1 (middle; 125 kbp) - hemi-parasitic Cuscuta 2 (innermost; 85 kbp) - holo-parasitic 33 Where are heterotrophs going evolutionarily?!? Evolutionary dead- end?! Too specialized to survive in the long term?! Drawings: Alison Colwell 34 17  11/11/24 Drawings: Alison Colwell 35 Drawings: Alison Colwell 36 18  11/11/24 Drawings: Alison Colwell 37 Drawings: Alison Colwell 38 19  11/11/24 Where are heterotrophs going evolutionarily?!? Perhaps they will eventually become so reduced and specialized that we will no longer recognize them as plants… Þ example of Plasmodium (the cause of malaria) - herbicides as potential treatments?! Drawings: Alison Colwell 39 BIO339: Plant Identification & Systematics Fall 2025 Identify 34-36 important plant families by sight Orchidaceae Araceae Corallorhiza maculata Lysichiton americanus Ericaceae Boraginaceae Elliottia pyroliflora Myosotis sylvatica 40 20  11/11/24 BIO339: Plant Identification & Systematics Fall 2025 Key unknown plants to species using published floras Knowledge of morphology is vital to plant identification 41 BIO339: Plant Identification & Systematics Fall 2025 Gain a greater appreciation for nature, and your connection Triticum aestivum with it. Hevea brasiliensis Wheat flour Natural rubber Saccharum Erythroxylum coca officinarum Cane sugar 42 21  11/11/24 BIO339: Plant Identification & Systematics Fall 2025 Gain a greater appreciation for nature, and your connection with it. 43 22