Tree survival
How do trees survive after shedding their leaves?
KALYAN
Certain plants are perennials and survive from year to year by matching their growth to the progression of the seasons or by suspending growth altogether during unfavourable times, such as winter or a dry season.
The resting bud consists of a short axis, with the shoot apex surrounded by modified unexpanded primordial leaves, which protect the shoot apex having the shoot apical meristem, especially from drying.
The cells in these leaves show marked frost resistance, similar to that of the embryo of the seed. In the case of herbaceous plants, the marked changes that occur during this unfavourable season are dying back of aerial parts altogether, leaving protected organs at or below the soil surface.
Many types of trees shed their leaves as a strategy to survive harsh weather conditions. In temperate forests , trees shed their leaves during autumn as cold weather approaches. In tropical and subtropical forests, trees shed their leaves at the onset of the dry season. Trees that lose all of their leaves for part of the year are known as deciduous trees.
Leaves are expensive organs for a tree to build and maintain. During winter (in cold climates) or the dry season (in warmer climates) it becomes difficult for the tree to maintain its water balance as there is less free water available in the soil. It is thus difficult for the tree to keep its leaves turgid and the cells of the tissues in the leaves would become damaged by the cold in temperate areas, or the heat in warmer areas. Instead of remaining actively growing during this time of the year the tree enters a dormant period.
Trees are adapted to the climate of the area where they grow. They do not wait for their leaves to be damaged by the harsh conditions of the winter or dry season. They prepare in advance for the onset of the unfavourable season by getting ready to lose their leaves.
Shedding leaves helps trees to conserve water and energy. This process is called abscission.
At the start of the abscission process, trees reabsorb valuable nutrients proteins and carbohydrates from their leaves and store them for later use in their branches or roots. Thus the leaf that is due to fall does not take these substances with it and an important part of the materials necessary to form leaves in the future is retained.Many types of trees shed their leaves as a strategy to survive cold or dry weather and so leaf shedding is a purposeful separation process and it will never leave the pant to die.
S. PALANIAPPAN
EditorResearch Journal of Biological Sciences
J.J. College of Arts and Science (Autonomous)
Pudukkottai, Tamil Nadu
