Epiphytes, saprophytes, and parasites

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Epiphytes, saprophytes, and parasites
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Epi phyte
Spanish moss (Tillandsia usneoides) on bald
cypress
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Absorbent leaf scales
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Tropical epiphytes tank bromeliads
Invertebrates associated with tank pools
mutualism?
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Using stable isotope methods, we found that the
Neotropical jumping spider Psecas chapoda
(Salticidae), which lives strictly associated
with the terrestrial bromeliad Bromelia balansae,
contributed 18 of the total nitrogen of its host
plant in a greenhouse experiment.
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Other bromeliadsin dry tropics, with xerophytic
foliage, CAM
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Orchidaceae Vanilla planifolia
Orchid aerial roots have absorptive outer layer
velamen
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Rhipsalis baccifera (mistletoe cactus the only
cactus native (sort of) to the eastern hemisphere
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Other epiphytic cacti Epiphyllum
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Hylocereus fruit
Note that seeds have germinated within
fruit (vivipary)
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Epiphytic ferns from tropics
to north temperate rainforests
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Clusia a strangler that begins life as a CAM
epiphyte (making it a hemiepiphyte)
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Indian pipe once thought to be a parasite, is
actually a saprophyte
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About 3000 species of vascular plants are
parasitic on other plants

• About 3000 species of angiosperms are parasitic
  on other vascular plants.
• What a world.

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Parasites can be hemiparasitic (taking only
water) or holoparasitic, obligate or facultative.
Mistletoe an obligate hemiparasite
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Parasitic plants attach to host xylem via a
structure called a haustorium
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A holoparasitic mistletoe, Quintral, is quite
damaging to its cactus host, but good for birds
Sole fruit disperser, Mimus tenca, eats and
promptly defecates
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Dodder (Cuscuta sp.) hemi- or holoparasite?
Photo by Steve Matson
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A local, facultative hemiparasite Castilleja
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Striga or witchweed can reduce crop yield 20-70
in Africa, Asia
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Step-by-step process of infection by Striga

• Striga seed germinates only in presence of a
  hydroquinone released by host roots
• Striga roots produce enzymes that attack surface
  of host roots
• Host roots triggered to produce Haustorium
  Inducing Factor (HIF)
• Haustorium produced on Striga root
• Haustorium attaches to host vascular tissue
• Hydroquinone inactivated by O2breaks down
  quickly in soil (in Striga infection,
  strigalactone produced)

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Diagram of Striga infection
Plant-Plant Communications Rhizosphere Signaling
between Parasitic Angiosperms and Their Hosts1
Elizabeth M. Estabrook and John I. Yoder
Plant Physiol. (1998) 116 1-7
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Note resistant strain shown in right-hand photos
(f,g,h,I,j)
Fig. 1 Rice roots harvested for the global
analysis of gene expression showing the phenotype
of the susceptible interaction between IAC 165
and Striga hermonthica and the resistant
interaction with Nipponbare. Development of
parasites on cultivar IAC 165 2 (a), 4 (b) and 11
d post-inoculation (dpi) (c). (d) A transverse
section through the parasite and host root at 4
dpi revealed that the endophyte had grown through
the cortex and breached the endodermis to begin
to form xylem-xylem continuity with the host. (e)
By 11 dpi the parasite had formed extensive
parasitehost xylem continuity and the haustorium
was fully formed. Development of parasites on the
resistant rice cultivar Nipponbare 2 (f), 4 (g),
and 11 dpi (h). (i) At 4 dpi a transverse section
through the parasite and host root showed that
the endophyte had grown through the cortex but
had not breached the endodermis. (j) At 11 dpi
the endophyte had encircled the endodermis but
had not penetrated the host vascular system. The
parasite haustorium had not differentiated. Bars,
500 µm (ac, fh) 100 µm (d, e, i, j).
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Australian Christmas tree parasitic on grass
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Holoparasites take water photosynthate
For example, Rafflesia, worlds largest single
flower (note flower is also endothermic)