Changing watering practices to improve tomato plant health

Climate change threatens crop production as rising temperatures, unstable rainfall patterns, and more insects and diseases endanger plant health and yields. Thus, there is growing pressure to identify ways to moderate these environmental effects, ideally without increasing the use of chemical pesticides. To address this challenge, Man-Qun Wang and colleagues examined how mechanically stimulating tomato plants with water droplets impacts their growth and might protect them from insect predation and fungal infection.

The researchers sprayed tomato plants with water twice daily and compared the effects of small droplets (200 micrometers, about the size of a computer monitor pixel) and large droplets (1,000 micrometers, about the diameter of a pinhead) versus no spray. They also covered the soil with a barrier to ensure the spray didn't influence how much water the roots received.

Structural observations revealed:

• Tomato plants sprayed with large water droplets were shorter and more compact than other groups.
• There were minimal visible differences between plants receiving small droplets or no spray.
• Fruit yield and quality were similar among the three groups.

Metabolic analysis revealed that tomato plants sprayed with large water droplets had:

• Significant changes in hormones involved in plant defenses, resulting in increased resistance to destruction by moth larvae or gray mold compared to plants that weren't sprayed.
• Higher levels of defense-mediating chlorogenic acid in their leaves compared to the other plant groups.
• Reduced emissions of volatile organic compounds compared with plants receiving no spray, which made them less attractive to egg-laying moths and resulted in 74% fewer eggs on the leaves.

Given these results, the researchers suggested that continued developments in water spray technologies and droplet atomization could improve agricultural practices, making farming greener and more efficient.