The white areas on water props that many people ask about appear to be undifferentiated tissue that forms in and around injured areas like granulation tissue in mammalian wounds, but in a plant. Some call it “callous”. Similar tissue seems to appear from the lenticels of stems. The water appears to cause the new tissue to remain white because it doesn’t dry out as it would out of water. I’m sure we have all seen this phenomenon in many cut plant stems when kept in water. I currently have an olive tree cutting that developed very similar granulation tissue after approximately 7-10 days in water. Then, suddenly, a root emerged from an area of the granulation tissue, followed within a few days by multiple roots. I will try to post pics.
by Marconjx