Abstract: Gap is the focus of grassland ecological research over the past few decades, which plays an important role in promoting recruitment and maintaining community structure and species diversity in grassland ecosystem. Many plant species require the gaps of specific dimension, shape, and duration for their successful germination, emergence and establishment. This paper introduced the concept, formation, and functional types of gap, and summarized the research progress on grassland gap. The related researches were mainly focused on the effects of gap size and type on regeneration, and the influences of gap on community structure and species diversity. As for the gap microenvironment, few studies were made on the soil difference between gap and non-gap, and the physiological and ecological mechanisms of gap as well as the responses of plant species to gap were poorly understand. It was suggested that the studies of gap microenvironment, the physiological and ecological characteristics of plant species in gaps, and the response mechanism of species regeneration to gap should be strengthened in the future.

Key words: Wheat seedlings, Zn, Cd, Element uptake