The link is in the article, but here it is[0]. >What role does PPO play in the plant, you might ask? In some plants, PPO plays a defensive role – for example,

The link is in the article, but here it is[0]. >What role does PPO play in the plant, you might ask? In some plants, PPO plays a defensive role – for example, tomatoes produce high levels of PPO when attacked by pests or pathogens. In contrast, apples produce very low levels of PPO, and only in very young fruit. Its presence is probably left over from apples of ages ago, playing no role in today’s apples. It sounds like the appendix or tail bones in humans. He does mention in the last paragraph that PPO's may be antioxidants, but whether PPO's are needed or not is not known. Unfortunately, if this takes off it will be much later down the line if we find out there are adverse side-effects. To be fair, there is currently no known health issues with GMO plants, AFAIK. [0] http://www.arcticapples.com/how-did-we-make-nonbrowning-apple/ http://www.arcticapples.com/how-did-we-make-nonbrowning-appl...