Question

why do insectivorous plants need to feed on insects when they are green and synthesize their food

Answer 1

Venus fly traps live in sandy wetlands in North and South Carolina, often among long-leaf pine trees. The needles from these pines fall to the ground, and when they decay, they contribute to an peaty, acidic soil environment. The combination of the acid and a general lack of organic matter in the soil creates a very nutrient-poor soil mix. Think of it as soil that lacks fertilizer.

This is great for the fly traps, because it is a difficult environment for other plants to grow in, but it means that they need to find other ways to bring in key nutrients like phosphorus and especially nitrogen. This is where trapping bugs is valuable; they serve as a nutrient-rich fertilizer to provide support for the photosynthesis that creates its energy stores.

The adaptation to trap insects to act as a fertilizer isn’t limited to Venus fly traps, and this is why you’ll see other carnivorous plants such as sundews and American pitcher plants living together with the fly traps. Likewise, carnivores in other environments, like sun pitchers on Brazilian tepuis or Nepenthes pitchers on southeast Asian rainforest share a proclivity for nutrient-poor soil with fly traps, even if the rest of their habitat seems very different.

Answer 2

insectivorous plants are green and autotrophs they photosynthesis for their food requirement but they grow on the areas where is lack of Nitrogen so to fulfill its need of Nitrogen they feed on insects they serve the nitrogen of insect to fulfill its nitrogen need