In order to be classified as a green plant, an organism should be eukaryotic, have double-membraned chloroplasts, cell walls, and go through the process of . Land plants likely evolved from . Plants have a life cycle that is called the alternation of generations. The two phases of this life cycle are the diploid stage and the stage. A plant structure that contains a full set of paired chromosomes is called a . There are two key transport tissues in plants. transports water from the roots to the rest of the plant, while phloem transports sugar and nutrients.