Friday, March 17, 2017

"Ghosts of the Plant Kingdom": Albinism in Plants

This is a backyard inspired post. Look at the tiny albino Mandaram (Bauhinia spp.) seedling we found today. Unfortunately the chances of survival of this beauty is slim.
1day old albino seedling of Hongkong Orchid Tree aka Purple Mandaram
(‪Phanera purpurea‬)
Albinism is the lack of pigment which causes characteristic paleness or whiteness. The incidence of albinism is known in many living species. Total albinism in plants is lethal; an albino seedling will die within days of sprouting once it has depleted the seed- food reserves due to its inability to photosynthesise. They shrivel in sunlight as they have no protection.

Left: White needles (folliage) of an albino redwood.
Right: Albino redwood tree next to its parent tree.
A chimera shoot of redwood, showing both albino and
pigmented needles.
However there are a few cases where albinism can produce remarkable, unique, and even long-living plants. Two famous examples being the albino redwood and the albino Adder's mouth orchid.  The albino redwood grows up as an offshoot of its parent tree, grafting its roots to the healthy parent's roots and drawing nutrients from the parental roots like a parasite. 
The albino Adder's mouth orchid have white flowers and pale leaves and are thought to survive due to a very small amount of chlorophyll in their leaves.
There are also reported cases of albiflora(white flower) and chimeras where individual shoots of a plant shows albinism.

True albinism (as opposed to chlorosis or reduced chlorophyll caused by poor plant nutrition) is a genetic condition and can be identified at a molecular level by the incomplete differentiation of chloroplast membranes, and by the complete or partial loss of chlorophyll. It is believed that albinos (and albiflora) are created by genetically recessive traits (opposite dominant, colorful, or chlorophyll pigmented trait).

Some interesting facts:
  1. Albino redwoods are a rare feature of California red wood forests. They are referred to as the "Ghosts of the forest" and their locations in many places are kept secret to keep poachers and souvenir hunters away!
  2. Albino redwoods have been found to absorb and accumulate toxic heavy metals nickel, copper and cadmium in them hence is a potential candidate for phyto-remediation. Parent tree-Albino relationship in redwoods may infact be a mutually beneficial one.
  3. Albinos occurs during tissue culture of many crop plants, for example androgenesis of cereals like wheat, barley etc. Though they are an unwanted complication in micropropogation and breeding programs, they are being studied to better understand the plastid genome, and better understand some transporter proteins.
Interesting Reads:
Albino seedling (Top) and its pigmented sibling (Bottom)