Studies on cold tolerance of rice, oryza sativa L. I.Description on types of cold injury and classifications of evaluation methods on cold tolerance in rice

Here is the first part of a series of papers to describe the studies on cold tolerance of rice.This part mainly describes types of cold injury and evaluation methods for cold tolerance.The types of cold injury can be divided into delaying injury and critical injury.Injuries at budding stage,seedling stage,booting stage,flowering stage,and filling stage can also be called based on the growth stage when the cold injury occurred.Various methods to evaluate cold tolerance at budding stage,seedling stage,booting stage,and flowering stage as well as under natural conditions were systematically introduced.The research progress of criteria relative to cold tolerance evaluation was also detailed.