How Does Luck Bamboo Grow with Just Water????

[Asagi]

Photosynthesis(most of the solid plant matter is carbon fixed from the air)...Lucky bamboo grown in water alone will eventually develop nutrient deficiencies which is why a lot of lucky bamboo plants look yellow/lime-green instead of a dark green and don't hold very many leaves. A lot of Asian stores sell fertilizer geared solely towards lucky bamboo plants. Eventually they will die if grown in water with no nutrients...however if you don't replace the water, things like dust and dead bugs can keep the plant alive.

[lunetunelover]

I think you already got the answer...photosynthesis. All plants have the capability to grow in water alone absorbing nutrients from the water, air, and light. As the roots grow, they will emit certain micro-organisms into the water that converts (like algae) into other food sources. I guess that's sort of a cannibalistic life. There are other micro-organisms in tap water (and the ambient air) as well. Some will do better in a soil mix of sorts, but not all require that.

[OwlKaMyst]

Apparently photosynthesis is not a viable answer because after giving that answer people are still questioning it. Has no one has ever seen an air fern? Not all plants need all three- light, soil, and water.
As far as the bamboo eventually becoming deficient, not so. I have a bamboo that I have had for over five years. It is tall, a deep healthy green and full of leaves. The only trouble it had was when I went away and someone forgot to water it. Once it got its water it recouped just fine.

[lunetunelover]

To reject photosynthesis as the answer means that one does not understand the process of photosynthesis.

Air ferns absorb their nutrients (including water aka humidity) from the air and light.

Not all plants need all THREE (light, soil, water) but they all need water and light.