Читать книгу Herbicides and Plant Physiology - Andrew H. Cobb - Страница 25

The survival and growth of weed populations are dependent upon successful pollination. Weed species tend to rely on non‐specific insect pollinators (e.g. dandelion) or are wind pollinated (e.g. grasses), so their survival is not dependent on the size of population of specific insect pollinators. Annual weeds are predominantly self‐pollinated and, when outcrossing does take place, pollination is achieved by wind or insects. This means that a single immigrant plant may lead to a large population of individuals, each as well adapted as the founder and successful in a given site. Occasional outcrossing will alter the genotype, which may aid the occupation of a new or changing niche. Furthermore, many weeds, unlike crops, begin producing seed while the plants are small and young, and continue to do so throughout the growth season. In this way the weed density and spectrum in an arable soil may change quickly.