Reproduction is the process by which living organisms multiply themselves. They do this through two major ways namely: asexually and sexually. Sexual reproduction involves two organisms (male and female) that each donate a gamete (sperm and egg). In plants, the sexual reproductive structure is the FLOWER. The male flower is called STAMEN, while the female flower is called PISTIL.
However, plants can also be propagated asexually by making use of certain plant parts including tubers, leaf etc. TUBER is a structure in plant specifically used to asexually reproduce plants like yam, potato, cassava etc.
you are using your shoulder muscle. The reason you are using this muscle is when you put your arm strait up there is no reason to use a bicep or tricep muscle.