Final answer:
The characteristic of a population of plants indicating asexual reproduction is identical traits in all individuals, as no genetic mixing occurs unlike in sexual reproduction which produces diverse phenotypes.
Step-by-step explanation:
The characteristic of a population of plants that would indicate they were produced by asexual reproduction is (C) Identical traits in all individuals. This is because asexual reproduction involves a single parent and does not involve the fusion of gametes, resulting in offspring that are genetically identical to the parent. Unlike sexual reproduction, which results in offspring with diverse phenotypes due to the combination of genetic material from two parents, asexual reproduction does not typically produce variation in traits unless a mutation occurs.
Moreover, sexual reproduction in plants can lead to higher adaptability and genetic diversity within a population, as observed in crop improvement and breeding systems that select for specific features such as 'non-shattering' heads in cereal grains. However, in asexual reproduction, variation can only come from mutations of DNA rather than the shuffling of alleles that occurs in sexual reproduction. Therefore, the presence of identical traits across a population is a clear indicator of asexual reproduction.