The paper presents AquaDust as a breakthrough for measuring leaf water potential in situ using fluorescent nanoparticles. But here’s the critical issue: the calibration of these nanoparticles depends on the osmotic potential of the apoplastic fluid they’re mixing with. The authors cite studies in maize and tomato, but they don’t address that cell wall properties, pore size, charge density, elasticity, vary dramatically between species, between developmental stages, and even between different leaves on the same plant under stress. If the nanoparticles are reporting based on swelling behavior that’s calibrated in one context but deployed in another, the water potential readings could be off by orders of magnitude. Without a way to recalibrate in planta for each genetic background and environmental condition, isn’t this just giving us beautifully precise measurements of something we can’t actually interpret?
