Time-resolved ultra-weak photon emission as germination performance indicator in single seedlings

As they grow, plant seedlings emit very small amount of light, the so-called ultraweak photon emissions (UPE). Numbering tens or hundreds of photons per second, this UPE radiation has been measured on groups of 10 to 1000s of seedlings growing together. Here, we set out to measure UPE on single germinating seeds, enabling the assessment of individual seeds. Here, UPE were measured in low-noise laboratories, enabling long-term, stable and reproduceable testing conditions. UPE recordings could in effect be performed on single germinating seedlings of mung beans, corn and wheat, also comparing measurements to 10-seed sample of mung beans. The data reveal differences between seedlings and plant species. The relation between the seedling's development - total length of roots plus leaflet - and the UPE data is presented in terms of the total photon counts as a function of seedling growth in time. These data were fitted in linear interpolation, for the tests with mung beans when related to the UPE slope (R² ~0.834). UPE versus growth correlation was weaker for tests conducted with single mung seedlings (R² <0.4), revealing individual variation and seedling movements during growth. For single corn, intermediates correlation coefficients R² were observed (0.572 <0.83), while single wheat seed data were more sparse (R²~0.62). Altogether the data show a general pattern of linear UPE to growth relationship, yet highlighting variations between plant species, which provide a benchmark for assessing the health of early seedlings.