What are the standards for strong rapeseed seedlings? Explained clearly in one article

(Agricultural Wealth Network) Morphological characteristics of robust rapeseed seedlings: the seedlings are short and sturdy, with shortened internodes and tightly arranged leaf order; the leaves are large but moderate, of normal green color, with thick and short petioles; the root system is well developed, with a thick and large main root, many fine branch roots, and many young tender roots, and a thick and short root crown; at transplanting, the "three-seven standard" is reached, that is, 7 green leaves, a seedling height of 23 cm, a root crown thickness of about 0.7 cm, an appropriate seedling age, many white roots, no leggy seedlings, and no pests or diseases.