Effects of low temperature stress

i. Black heart:

• It is a form of winter injury in which pith is killed, heart wood and xylem is darkened shiny black while the cambium and bark remain alive

ii. Crotch injury

• It is characterized by killing of bark and cambium tissues in the crotches of both large and small branches
• Bark cells die, crack and food supply is disturbed and plants die

iii. Crown or collar injury

• Usual type of damage caused by severe frost is at the ground level
• In such cases, bark of young trees is killed and cracked open
• The inner sap carrying tissue is ruptured through freezing
• It may also extend up to the roots
• Bridge grafting and painting over damaged portion overcome this

iv. Splitting of bark

• Generally caused by severe frost occurrence and it may extend to the entire length of branches or trunk under extreme condition

v. Killing bark of shoot & young branches

• Tropical and sub-tropical fruit trees may be damaged by frost in early winter or early spring
• In fruit like mango, flower may be killed while in other fruits like citrus and papaya, even fruits may be injured

vi. Frost damage/ winter kill

• Deciduous fruit trees shed their leaves during winter and go to dormancy
• But the evergreen fruit trees don’t go to dormancy so they are severally damaged (tender shoots, fruits, etc.)
• Frost affected fruit shows dry patches and bear tasteless juices
• Tasteless juice in guava and citrus is due to thin layer of ice crystals deposited on soil and plant surface
• The young plant and top shoot may be killed immediately.