1. Which plants demonstrate primary and/or secondary growth? All plants have pri
ID: 202280 • Letter: 1
Question
1. Which plants demonstrate primary and/or secondary growth? All plants have primary growth and some show secondary growth later in their life cycle. On a three year old stem or root, where and when would you observe primary growth? secondary growth? 2 Which plant tissues produce primary growth? Secondary growth? 3. What are the results (tissue formed and cell types) of primary and secondary growth. 4. Keep in mind that parenchyma cells can undergo dedifferentiation to become meristematic cells -divide by - develop into primary growth forming primary roots or stems. This is controlled by plant hormones. The callus tissue you are observing on your cuttings forming adventitious roots is an example.Explanation / Answer
1. Annuals are plants that grow and reproduce in span of one year and complete their life cycles. Biennials are plants that show vegetative growth in the first year and reproductive growth during the second year and complete life cycle within two years. Perennials are plants that grow more than two years. These plants grow and reproduce continuously throughout their life. Perennials initially exhibit primary growth. During secondary growth, these plants add the bulk to the stems resulting in increase in diameter of trunk as they grow into trees. Primary growth is observed in both the roots and stem early years of plant life. When the plant grows into a tree the roots and stem exhibit secondary growth due to adding the bulk by vascular tissues.
2. Primary meristems located at the shoot apex, root cap region and in lateral buds of stems and exhibit primary growth. These meristematic cels undergo celldivisions continuously to differentiate to form various cells and plant parts. The scondary meristems include cambium and phellogen or cork camnium that produce cells enabling the tree to grow in thickness.
3. Primary tissues result in growth of main tap root due to division of meristematic cells in root cap region. The meristes in shoot apex allows the plant to grow in height. The meristems of lateral buds produces the branches. The secondary meristems of cambium and cork cambium of root and stems add bulk and help to increase in diameter of roots and stem.
4. The parenchyma cells of meristems have special feature into divide and differentiate into root and shoot cells. Callus is undifferentiated mass of parenchyma cells that differentiate to form shoot and roots. The adventitious roots are formed from callus by the influence of plant hormones cytokinins.
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