dr. sarita srivastava chaudhary mahadeo prasad degree college allahabad
TRANSCRIPT
Growth and Growth hormones
Dr. Sarita SrivastavaChaudhary Mahadeo Prasad Degree College
Allahabad
Animal vs. plant growth
Development: is a series of change which an organism goes through in his life cycle.
Development is associated with morphogenesis and differentiation
During growth New cells are added by cell division Organism grows in size Increase in weigh Protoplasm multiplicates Irreversible permanent increase in volume takes
place
Development leads to growth
Growth and Development
Definition-Growth: permanent and irreversible change in size of the cell, organ or whole organism usually accompanied with increase in dry weight .
Types of Plant Growth1. Determinate growth : As you grow and develop from childhood you get taller and bigger overall. But at some point you reach a maximum height. This type of limited growth is called determinate growth. What it means is that once you have reached your maximum height (which is determined by your genetics), you can't grow any taller. This is something that you have no control over.2. Indeterminate growth: Plants, unlike animals, have indeterminate growth. This means that they can continue to grow taller as long as they are alive. Most plants tend to slow their growth at some point, but as long as they wish to keep growing they may do so.
All plants experience what is called primary growth. Primary growth is the upward growth of the stem and the downward growth of the roots. It is the type of growth that makes a plant longer.
Some plants experience an additional type of growth called secondary growth. This occurs in plants known as dicots, such as trees, shrubs, and vines. Secondary growth is the outward or lateral growth of a plant, which makes it thicker and wider. Dicots need secondary growth because they tend to grow taller than other plants and need the extra support. Without secondary growth, a tall pine tree would be just like a very long blade of grass.
Process of growthGrowth involves meristematic changes1.Cell division :
occurs due to meristems, apical intercalary and lateral
2.Cell enlargement: 3.Cell maturation
Meristematic and physiological changes during the process of growth
Cell is metabolically highly active Cellular mass of cell increases Replication of genetic material takes place Growth basically due to the mitotic cell
division Mitochondria and chloroplast duplicate on
their own Two daughter cells are formed which are
half the size of the mother cell These cells proceed for cell enlargement
Cell division:
Cells increase in size due to vacuolation i.e. absorption of water
The central vacuole pushes the cytoplasm to the periphery of cell
The cell wall becomes thin New wall material is being synthesized to cope up with
the cell enlargement It is said that cell enlargement is governed by osmosis DPD=OP-TP Wall pressure is reduced in the vacuolating cells due
to increased plasticity of cell walls this results in absorption of water from the neighboring cells
Cell enlargement is associated with absorption of water, synthesis of new cytoplasm and cell wall material
Cell enlargement
Development of specialized mature tissues E.g. meristematic cells of leaf epidermis
differentiates to form: Guard cells Trichomes Glands Epidermal cells Cell differentiation depends upon the
growth factors
Cell maturation
Phases of growth Growth Curve is Sigmoid
Growth Curve : Lag Phase Log Phase Steady Phase
Instruments An auxanometer (Gr. auxain, "to grow" + metron, "measure") is an apparatus for measuring increase or rate of growth in plants.
A crescograph is a device for measuring growth in plants. It was invented in the early 20th century by Sir Jagadish Chandra Bose - a Bengali polymath, physicist, biologist, botanist, archaeologist.
Factors affecting growth
Light : Etiolation Photomorphogenesis Seedling growth, seed germination,
flowering Temperature: thermoperiodicity-fluctuation in temp
affectin growth 25 ˚C day temp-12˚C night Water: water stress stops growth
Environmental factors
C/N ratio More nitrogen : more protoplasm, less mechanical tissues, vigorous vegetative growth, shoot is large in compared to roots leaves are large and soft Succulent and dark green in colour Less nitrogen and more carbohydrate
favors more wall synthesis, less protoplasm and more roots as compared to shoot
Nutritional factors
The genes of an individual determines its type
Hormonal factors: Growth is regulated by growth
hormones
Genetic factors
What is difference between Growth hormones and growth regulators
Definition of Growth hormones:
Growth hormonesWent and Thinmann 1937
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