It goes without saying that leaves are vital to the existence of any photosynthetic plant. They are, after all, the food making organs. This is why plants go to great lengths to protect them. Losing leaves can be extremely costly. One of the most intriguing methods of anti-herbivory in plants is known as delayed greening. Flushes of new growth bathed in reds, whites, and light greens can color forests from top to bottom.
Delayed greening is a matter of resource conservation and herbivore protection. The cellular machinery that makes photosynthesis possible is costly to produce. It requires large amounts of nutrients, such as nitrogen and phosphorus, that are often in short supply. If a plant can help it, its best to avoid losing a leaf chock full of these precious materials. Delayed greening does just that.
Photo by T.Voekler licensed under CC BY-SA 3.0
Essentially, the process proceeds exactly as it sounds. Young shoots and leaves gradually expand over time, becoming more green as they grow tougher and better defended. When a plant packs its leaves full of photosynthetic machinery right out of the gates, when leaves are small and tender, it runs the risk of loosing all of its investment to a hungry herbivore. In contrast, non-photosynthetic leaves are thought to be less palatable to herbivores because they simply do not have the nutritional content of photosynthetic leaves.
By delaying the development of chlorophyll until the leaf is fully expanded and a bit tougher, some plants are maximizing the chances of successfully increasing their photosynthetic capacity over time. Research has shown that plants that exhibit the delayed greening strategy experience significant reductions in the amount of herbivory over time. What they lose with the lack of photosynthesis early on they make up for in the fact that such leaves last longer.