While we're hunkering down to pull the rug from beneath the epidemic, some researchers are working to develop life support systems for plants in order to help them, too, face diseases.
A team of researchers from MIT has developed a precision microinjection procedure that can help deliver water, nutrients, and medicine to plants struggling against diseases affecting their circulatory systems. Such plagues are untreatable by normal pesticides, the team explains, and there are already outbreaks in several areas of the world affecting crops such as oranges, olives, and bananas.
Healthy plants are happy plants
"We wanted to solve the technical problem of how you can have precise access to the plant vasculature," explains graduate student Yunteng Cao, lead author of the paper.
One of the main hurdles they had to overcome is that we simply didn't have any needles fit for the job. Similar processes today use "needles that are very large and very invasive, and that results in damaging the plant," Cao explains. So the team turned to previous research that used silk-based materials to create microneedles for vaccine applications. These needles were designed to dissolve inside the human body after use, but plants contain much less moisture internally than our organisms. The team had to change the material in order to make it usable in plants but maintained silk as a starting point for its desirable chemical and biological properties.
They came up with what they call phytoinjectors (in Greek "phyton" means "plant"), which can be produced in a variety of sizes and shapes. These needles can be used to accurately deliver compounds to specific parts of plants, such as roots, stems, leaves. They're small enough to allow researchers to target the xylem (the vascular tissue involved in water transportation from roots to canopy) or phloem (the vascular tissue that circulates metabolites throughout the plant), both of which are quite small.
The team successfully tested their phytoinjectors in the lab on tomato and tobacco plants, and are confident that it can be adapted to almost any crop. The project started in response to a request from the U.S. Department of Agriculture for ideas on how to address the citrus greening crisis, which is threatening the collapse of a $9 billion industry says MIT professor Benedetto Marelli, co-author of the paper. This disease is caused by insect-borne bacteria and there is currently no known cure for it (as we don't have an effective way to administer medication internally for the plants). Roots are particularly affected by the disease, and particularly hard to treat, he explains.
But the technique's applications aren't only medical. It can also be used to take samples from plants, the team explains, providing a way for labs to analyze them with minimal disruption.
"We think this is a new tool that can be used by plant biologists and bioengineers to better understand transport phenomena in plants," Cao says. It can be used "to deliver payloads into plants, and this can solve several problems. For example, you can think about delivering micronutrients, or you can think about delivering genes, to change the gene expression of the plant or to basically engineer a plant."
The technique still relies on precision equipment, so it's not yet practical for large-scale agricultural applications, but the team hopes it can be used to, for example, create disease-resistant versions of crops today.
They were also able to modify a dart gun mounted to a small drone to fire microneedles into plants in the field. Such a process might be automated using autonomous vehicles in the future, says Marelli, and could prove more practical for agricultural-scale use.
The paper "Precision Delivery of Multiscale Payloads to Tissue‐Specific Targets in Plants" has been published in the journal Advanced Science.
