How do carnivorous plants digest their meal and remove the waste after digestion?

Carnivorous plants capture small insects and digest them to obtain nutrients . Some of the carnivorous plants catch the insects `actively' by rapid movement of the trap mechanism (for example, Venus fly trap) while a large majority are `passive' catchers where the insect falls into pitcher-like structures (for example, Pitcher plant) or stick on to mucilage (for example, Sundews). Digestion proceeds after catching the insect. Some plant species produce and secrete digestive enzymes on to the trapped insect and digest them. Most of the active trap plants belong to this category. Some plant species depend on bacteria to produce these digestive enzymes. Some plant species use a combination of both the above methods.

Most of the passive trap plants that use mucilage `sticky traps' are associated with `killer bugs' to digest their catch. These insects eat the catch and excrete their faeces on the plant surface. The plants absorb nutrients from the faeces. Amazingly, these associated killer bugs do not get trapped.In active trap plant species, enzyme secretion is triggered upon catching the prey. n Pitcher plants, when the trap is formed, the bottom is filled with a mixture of digestive enzymes, which slowly declines if no insect is trapped. Later, when insects get trapped, enzyme secretion is activated . It was also identified that these plants even adjust the pH (acidity) to favour the digestive enzymes. Some plant species produce free oxygen radicals to non-enzymatically digest proteins (for example, the protein myosin) or to predispose proteins to digestion by proteases.The tough exoskeleton of insects is usually not digested and when traps are open, these are blown away by the wind. In pitcher plant species, these just accumulate at the bottom until the trap decomposes later. All traps have special structures and transporters to absorb nutrients.