Final answer:
Plant species where individuals produce only male or female gametophytes are called heterosporous. These species include seed plants like conifers and flowering plants where microspores and megaspores develop into male and female gametophytes, respectively.
Step-by-step explanation:
Plant species in which some individuals produce only male gametophytes, while others produce only female gametophytes are referred to as heterosporous. These plants produce two different types of spores: microspores and megaspores. Microspores develop into the male gametophytes that generate sperm, while megaspores develop into female gametophytes that produce eggs. This is in contrast to homosporous plants, where a single type of spore develops into gametophytes that produce both male and female gametes.
Seed plants are an example of heterosporous plants and are characterized by a dominant sporophyte generation and reduced male and female gametophytes. These gametophytes mature within the spores, they are typically not free-living, and in the case of seed plants, they are often enclosed in the tissues of the sporophyte, as seen in flowering plants and gymnosperms such as conifers and cycads.