The idea to reverse-engineer the plant system as a whole is fascinating to think about. But it would be extremely difficult to do so because the entire plant system has evolved around the phenomenon of absorbing water via roots and transpiring out from the leaves. Few exceptions like orchids exist, but they also don’t transpire the water out of the roots, they absorb it with their leaves and stems and use water for normal physiological processes as all other plants do.
Orchids, more specifically vascular epiphytes have anatomical and morphological adaptations in the leaves, stems and roots that allow them to absorb water from the environment independent of direct contact with the soil. They have thickened cuticles, stomata surrounded by trichomes, sympodial growth (axial branching), and aerial root development to meet this feat. Other features like succulent leaves and the growth of pseudobulbs also make orchids better adapted for water intake from the existing moisture .
Hence, we can exploit the anatomical and morphological features of the orchids to develop plants that can soak up water from the environment. However, this is only half the job done.
Can we, as asked in the session, engineer the plants to release water into the soil?
Actually, there is a plant physiological process of ‘exudation’ that we can look into if we want to make plants expel stuff from their roots. Root exudation is the process that allows carbon transport to roots and the movement of solutes and molecules from roots to the soil. Exudation is thought to play a key role in maintaining the root microbiome of the plants and hence maintaining their relationship with the environment. This occurs at the tips of the roots. This involves a turgor pressure-driven unloading from the phloem, that occurs through plasmodesmata, and it involves mass flow and diffusion. Low-molecular-weight solutes and proteins are released from the phloem-pole pericycle (the area of the root tip). While proteins are released in discrete pulses, low weight solutes are released without any restrictions .
Theoretically, developing a plant system that takes up water from the air and releases it into the soil should therefore be possible. As a starting principle, we can use the following framework:
First, borrow the physiological and anatomical signature of water uptake from the epiphytes. ENgineer it into a new plant system to copy the orchids.