Growth

• Growth is, a quantitative term, an irreversible increase in number, volume (size) or weight of cell, tissue or organ in plant life cycle.
• It involves

Cell division in meristems, by increasing cell number, increases the potential for growth.

• However, it is cell expansion that accounts for the actual increase in plant mass.
• Together, these processes contribute to plant form.

Exceptions ： seedling dry weight less than the seed during germination. Megaspore formation（ 4→1）

Development

• Development refers to the sum of all of the changes that an organism goes through in its life cycle, including growth and differentiation. Ultimately, development is an expression of the genetic program that directs the activities and interactions of individual cells.
• Leaf： leaf primordium →young →mature leaf
• Root： primordium →young→root system
• Fruit ： fertilized egg→young→ripened fruit

Differentiation:

• The specialization of cells with the same set of genetic instructions to produce a diversity of cell types is called differentiation.

Types of Growth

Classified by Developmental Stages Primary growth:

• Apical meristems extend roots and shoots by giving rise to the primary plant body Secondary growth:
• Lateral meristems add girth by producing secondary vascular tissue and periderm

A meristem is the tissue in most plants consisting of undifferentiated cells (meristematic cells), found in zones of the plant where growth can take place.

Apical meristems

• The apical meristem, or growing tip, is a completely undifferentiated meristematic tissue found
• in the buds and growing tips of roots in plants.
• Its main function is to begin growth of new cells in young seedlings at the tips of roots and shoots (forming buds, among other things).
• Specifically, an active apical meristem lays down a growing root or shoot behind itself, pushing
• itself forward.