How genetic variation in chloroplast DNA lead to variegation in plant leaves. How might leaf variegation be a disadvantage for plants? Can you think of any possible advantage?
Answer:
ariegated regions lack chloroplasts so do not reflect green light. This reduced chlorophyll level allows small amounts of other pigments like the yellow pigment xanthophyll to show up or the lack of chloroplast can be found with no other pigments. Hostas have areas like this and zones with no pigments are white. They absorb enough light in the green areas for the plant to transform light energy to chemical energy and support the entire plant’s nonphotosynthetic parts but they may grow slower than an all green version of the plant.
This slower growth would let all green plants out compete them by growing faster and crowding them out if there were no positive selective factors to retain white leaf patterns.
The markings may serve a function. White clover has a V-shaped clear mark on each leaflet. Clover leaf markings may help attract pollinators. Pollinators that recognize the plants offering the best nectar have an advantage in gathering more of this nectar.
Other plants have nongreen veins. There are no cells with chlorophyll on or beneath the veins making the leaf appear patterned like aroids or milk thistles.
These leaf markings may warn herbivores of bitter toxic metabolites so drive away predators before the plant suffers leaf damage from herbivores checking to see if the plant is bitter. Green plants must be sampled to determine bitterness so herbivore’s learning avoidance may help variegated plants compete with the all green growth rate by having less leaf loss.
