Answer:
Moss plants are short because they absorb all the required water from the environment and they do not have xylem tissue to provide them strength.
Step-by-step explanation:
Mosses are flowerless plants that are usually very short (4-5 cm). They are found as green clumps or mats in damp locations. As mosses are flowerless, they produce spores and require moisture for reproduction. Although mosses have leaves and stem, but they do not have true roots. They obtain water for their needs from the outer environment using their leaves and stem. Additionally, mosses do not have lignin in cell wall that provide the rigidity to the cells. Lacking the supportive backbone and efficient system for water transport mosses are short than other plants.