Achlorophyllous Plants

Indian Pipes (Monotropa uniflora). This cluster of achlorophyllous plants
is pushing through the leaves in early summer.  
Rowan County, North Carolina. 

When I think of plants I think green.  But there are some plants that never turn green because they do not make chlorophyll.  They are achlorophyllous.  Achlorophyllous plants come in a wide range of colors from white, to yellow, to pink but they all share a common feature.  Since they do not make chlorophyll they cannot carry out photosynthesis.  These plants have to get their organic nutrients from another source.  

How do these plants get their nutrients?  It was long thought that some achlorophyllous plants were saprotrophs, absorbing their nutrients from decaying organic material in the soil. It is now known they actually get nutrients from fungi.  The fungi are in a symbiotic relationship with a photosynthetic plant, often a tree.  The tree provides organic nutrients to the fungus and the fungus transfers water and inorganic nutrients to the tree so both benefit. Our achlorophyllous plant parasitizes the fungus for nutrients without providing a benefit to the fungus.  This type of nutrition is called mycohetertropy.  But not all achlorophyllous plants are mycoheterotrophs.  Some directly parasitize a photosynthetic plant by penetrating the root or stem and stealing nutrients.

Indian Pipes turning black after flowering.
Blue Ridge Parkway, Watauga County, North Carolina. 

Indian Pipe (Monotropa uniflora) is a mycoheterotroph in the Ericaceae, the same family as Azalea and Blueberry.  This widespread plant is found in North America, South America and Asia. Another common name for Monotropa uniflora is Ghost Plant because the whole plant is ghostly white.  Indian Pipe often grows under beech trees where its fungal host is associated with the beech. The Indian Pipe plant is 4-8 inches tall with a nodding flower and small leaves. Highly reduced leaves are a feature of many achlorophyllous plants because they do not carry out photosynthesis and do not need a large leaf area.  After flowering the Indian Pipe stem and leaves turn black. 

Dodder (Cuscuta sp.) in flower.  The host plant is Muscadine (Vitis sp.)
Jackson Park, Henderson County, North Carolina. 

A truly bizarre parasitic achlorophyllous plant is Dodder (Cuscuta sp). Dodder is in the same family as Morning Glory (Convolvulus sp.) and has thin yellow stems that drape over its host plant like colorful spaghetti.  The leaves of Dodder are reduced to minute scales on the stem.  There are more than 100 species of Dodder with the highest diversity in the tropics.  Dodder in North Carolina is represented by 8-10 species and they all are annuals growing from seed each spring.  The Dodder seedling locates its host by detecting volatile organic molecules its host releases. The seedling then grows over the surface of the host and invades the stem to extract nutrients.  Dodder parasitizes a number of crops and causes significant economic damage.  Dodder has a number of other interesting common names like; Witch’s Hair, Love Vine and Devil’s Guts. 

Dodder growing on Sand Live Oak (Quercus geminata).
Palm Beach County, Florida. 

A large stand of Dodder draping over Sand Live Oak.
Palm Beach County, Florida. 

Beechdrops (Epiphagus virginiana) is classified in the Family Orobanchaceae and is a parasite on American Beech (Fagus grandifolia).  The genus for Beechdrops is from the Greek “epi” meaning on and the scientific name of American Beech, Fagus. The specific name virginiana came from where the first specimen was described but this plant is found throughout eastern North America.  Beechdrops directly parasitizes the roots of American Beech and extracts nutrients. Beechdrops have a brown stem sporting tiny scale-like leaves. Beechdrops make light purple flowers that appear in summer. 

 

Beechdrops in flower.
Rowan County, North Carolina. 

Conopholis americana, Cancer Root, is another member of the Orobanchaceae.  Like Beechdrops, Cancer Root directly parasitizes trees, in this case Oaks (Quercus sp.).  Cancer Root has medical properties and can be made into an astringent tea used to treat bleeding and menopausal symptoms.  Ironically, this plant is not used to treat cancer.  An obsolete, racist common name for this plant is Squaw Root.  Another common name for this parasite is Bear Corn because it is reported to be a favorite food of bears awakening from hibernation.   

Cancer Root (Conopholis americana).
Blue Ridge Parkway, Watauga County, North Carolina. 

Corallorhiza, is a genus of mycoheterotrophic orchid with 11 species in North America.  The common name Coral Root comes from its branched, underground stem that resembles coral.  Corallorhiza has greatly reduced leaves like many of the achlorophyllous plants and a reddish-brown stem.  Wasp pollinated purple flowers are borne on the pink stem.  

Western Coral Root (Corallorhiza mertensiana).
Crater Lake National Park, Oregon.  

Closeup of Western Coral Root with flower buds
that are about to open.
Crater Lake National Park, Oregon. 

Flower of Western Coral Root.
Crater Lake National Park, Oregon. 

I think achlorophyllous plants are interesting because they have taken a different path from other plants.  Despite their lack of chlorophyll, they are all closely related to plants which can do photosynthesis.  Achlorophyllous plants have highly reduced leaves and their chloroplasts have lost many of the genes for photosynthesis.  Achlorophyllous plants are a fascinating slice of life’s rich diversity.