The correct option is Both 1 and 2.
Explanation
Plant growth is defined as an irreversible permanent increase in the size of an organ, its parts, or an individual cell. Because growth is the result of metabolism, it can be measured by a variety of parameters including fresh weight, dry weight, length, area, volume, and cell number.
Statement 1 is Correct:
One of the primary ways to measure growth is by the increase in the number of cells. A single maize root apical meristem can give rise to more than 17,500 new cells per hour. This demonstrates the high capacity for cell division in meristematic tissues.
Statement 2 is Correct:
Growth is also measured by the increase in cell size (volume). Cells in a watermelon may increase in size by up to 3,50,000 times. This example illustrates growth driven by cell enlargement rather than just cell division.
Key Takeaway:
Cellular growth in plants is manifested differently depending on the tissue and species: it can be a massive increase in cell number (e.g., maize root meristem) or a massive increase in cell size (e.g., watermelon).