Cold attack damage (chilling injury)

also known as cold damage. A phenomenon in which a plant is harmed or even killed by a low temperature above 0C. The critical temperatures of different plants vary, which is related to the growth conditions of their origin. Critical temperature is also related to the time of low temperature. For example, cucumber leaves can survive for 1 week at 10 degrees C, wilt for 3 days at 8 degrees C, and wilt within a few hours at 5 degrees C. In addition, cold damage often does not manifest itself at the time of the victim, but symptoms only occur when the temperature picks up. There are three types: (1) direct injury: the injury occurs faster and shows damage within a few hours or at least one day. It is generally believed that it is caused by a sudden increase in membrane permeability, resulting in leakage of soluble substances in cells. (2) Indirect injury: is caused by slow cooling, low temperature stress can last up to a few days or even weeks. Damage occurs when metabolic disorders occur. (3) Secondary coercion injury: because the root at low temperature reduced the absorption of water, can not supplement the consumption of steaming, and eventually dehydrate the plant leading to death. When an abscision layer plant leaves, several layers of thin-walled cells at the base of the leaf handle form a structure that adapts to the deciduous leaves. Before the arrival of the bad season (autumn and winter), a series of internal changes occur in the leaves, making the original green leaves gradually turn yellow, while at the same time at the base of the leaf handle there is a layer of small thin-walled cells across the leaf handle after multiple divisions, forming an out-of-area (several thin-walled cell layers). Later in the range of the out-of-area further differentiation to produce the strative and protective layer. The outer layer is on one side of the near-leaf handle, for two or more layers of cell layers stacked together, the intercellular layer mucus and decomposition, and even some of the cell's primary wall is dissolved, and cause the ionosthroid cells to separate from each other, only the bulging part of the tube is also connected with the branch, so the support is greatly reduced, because of the gravitational action of the blade itself or wind, the leaf handle is broken at the ionum, resulting in the phenomenon of deciduous leaves. Beneath the ionosphere is a protective layer, where cell wall wood is bolted, and sometimes substances such as glial and wood are deposited on the walls and cell gaps of these cells to protect the broken marks (i.e. leaf marks) after the leaves fall off. Some plants continue to produce periskin under the scar after deciduous leaves to enhance their protective function. The ionosphere can be produced not only at the base of the leaf handle, but also under certain conditions, the base of the flower handle and the fruit handle will also appear, causing the phenomenon of falling flowers and fruit falling fruit. Such as cotton bells and fruit trees fall flowers and fruit. Endogenous hormones
ethylene
which exist in plants can stimulate the formation of the outer layer, causing leaves, fruits and flowers to fall off (see Shedding).