Evaluation of seedling size following germination using computer-aided analysis of digital images from a flat-bed scanner

Early seedling growth rate can be used to estimate seed vigor for small-seeded vegetable and flower seeds. However, hand measurement of small seedlings is tedious and difficult to reproduce among analysts. Computer-aided analysis digital images of seedlings should improve accuracy and reproducibility. A flat-bed scanner fitted with base and top lighting provided high resolution images of even small-seeded species like petunia [Petunia xhybrida 'Blue Picotee' (Hort) Vilm.] and lisianthus [Eustoma grandiflorum 'Mariachi Pure White' (Raf.) Shinn]. Uniform lighting was provided and images were captured and analyzed in less than 2 minutes. A clear, cellulose film was used as the germination substrate in petri dish germination assays to facilitate capturing images with a flat-bed scanner. The transparent medium permitted seedlings to be imaged without removal from the petri dish and also allowed for repeated measures of the same seedlings in order to calculate growth rate. Six species evaluated in this study included cauliflower (Brassica oleracea L., var. Botrytis), tomato (Lycopersicon esculentum Mill. New Yorker'), pepper (Capsicum annuum L. 'North Star'), impatiens [Impatiens walleriana Hook. f. 'Impact Lavender'], vinca [Catharanthus roseus (L.) G. Don. 'Little Bright Eye'], and marigold (Tagetespatula L. 'Little Devil Flame'). For germination and early seedling growth, the cellulose film compared favorably with other standard germination media (blue blotter and germination paper) for five of the six species tested. Computer analysis of seedling length was possible for all six species and was statistically similar to hand measurements averaged for three analysts.