Plant Diversity ‐ Biol 3601 Lecture 14, Chapter 19 Characteristics of fungi Notes for students Lecture Topics • Characteristics of fungi o Ecology o Body structure o Reproduction o Origins Why study fungi in a plant class? • They are similar life history patterns as plants • Not covered in other courses • Endophytic fungi protect plants • Mycorhizae form beneficial relationship with plants • Decomposers enrich soil with nutrients • Pathogenic fungi cause disease • Beneficial service to us Dutch Elm disease is caused by fungi • American Elm planted widely because of rapid growth and stress tolerance • DED introduced from Europe in 30’s • Killed ½ trees in U.S. • Transmitted by bark beetles o Ulmus americana o American Elm • Plant responds to infection by plugging xylem • Tree dies in a month • Form spores under the bark that stick to emerging adult beetles • Also spread through roots that have merged and share xylem o Page 414 Prevention and cures? • Sever root connections with adjacent trees • Frequent pruning of dead wood • Fungicide • Insecticides • Traps with beetle pheromones • Mix up tree species in plantings • Breed resistant trees o Ophiostoma himal‐ulmi Fungi form symbiotic relationships with plants • 80% of vascular plants form mutualistic relationships with two kinds of mychorrhizae • Endomycorrhizae penetrate roots • Form arbuscles that press against plant cell membranes and obtain nutrients • Ectomycorrhizae emit hormone that causes branching • Fu
ungus surrounds root in a sheath called
d a mantle Benefits tto the plant? • Exxtension of th
he root system
m • In
ncreased uptaake of water aand nutrientss • Produces fewe
er root hairs by disease • Protects plant from attack b
body Endophyttic fungi live iin the plant b
Fungi form
m symbiotic rrelationshipss with cyanob
bacteria or alggae – lichen
• Upper cortex: protective laayer of gelatin
nized fungal h
hyphae • Photobiont layyer: photobiont wraped in hyphae • Medulla: loos
M
ungal hyphae serve as storage area ely packed fu
• Lo
ower cortex: covered with
h rhizines for aadherence to
o substrate • Fu
ungus penetrrates photobiont with haustorium •
Lichens caan persist in h
harsh environ
nments How do w
we benefit fro
om fungi? • Su
upplied first aantibiotic, penicillin • Im
mportant in th
he production
n of bread, w
wine, beer, bleeu cheese • Decomposers 9.10 o Fig. 19
o Penicilllium Fungal fuel? onia • Researcher collected branches of an anccient tree speecies in Patago
ndophytic fun
ngi grew out tthat produces a chemical similar to dieesel oil, called "myco‐dieseel” • En
• Etthanol = Plant‐> processing ‐> fuel • “M
Myco‐diesel” = Plant‐> fueel • Sttrobel et al. 2
2008 What do tthey eat? • • • Unique attributes? • Nuclear envelope remains intact during mitosis and meiosis (some protists) •
Straube et al. 2005. The EMBO Journal 24, 1674–1685, doi:10.1038/sj.emboj.7600644 • Cell wall made of chitin (arthropods) Body structure • Multicellular eukaryotes • Composed of long filaments called hyphae • Two kinds: o Septate ƒ Fig. 19.1 A mass of hyphae is called mycelium • Fig. 19.1 o mycelium o Fruiting body How do they eat? • Secrete enzymes that break down complex organic molecules • Abosrb small molecules • Pass through plasm membrane by diffusion or active transport proteins Mode of nutrition • Saprobes • Parasites • Mutualists •
Predators o When loop is agitated, it swells o Traps prey in <1 sec ƒ Fig. 19.2 ƒ Anthrobotrys anchonia Fungi reproduce by spores • Sexual spores are formed in the fruiting body • Asexual spores bud off conidia • Spores disperse fungi to new locations • Help survive adverse conditions (dehydration and freezing) Unusual phases in reproduction • Normal sex has four phases o Plasmogamy – when the cytoplasm of two haploid hyphae fuse (1n) o Dikaryotic phase – when two different nuclei share the same cell after plasmogamy (1n + 1n) o Karyogamy – when the nuclei in dikaryotic hyphae fuse (2n) o Meiosis (1n) • Parasexuality – after karyogamy, half of the chromosomes are gradually lost – a process called haploidization Evolution of fungi • Earliest fossils are 540 myo • Soft bodies don’t fossilize well • Using a molecular clock, fungi appeared about 1.5 bya • Must have been aquatic because invasion of land occurred 700 mya • Mycorrhizae and lichens helped plants become established on land • Molecular data suggests fungi are more closely related to animals than plants • Evolved from a flagellated protists that absorbed nutrients • Choanoflagellates closely resemble ancestral protist • Exist as single cells or colonies • Feeding cells like sponges • Form symbiotic relationships with photosynthesizers o Fig. 19.3