Final answer:
The change observed in part a of the experiment demonstrates the structure and function of a carnation's stem, including its support and transport functions. The stem consists of dermal, vascular, and ground tissues, with primary and secondary growth contributing to stem length and thickness. Annual rings in stems can be used to estimate a tree's age, and there are various examples of modified stems in different plants.
Step-by-step explanation:
The change observed in part a of the experiment demonstrates the structure and function of a carnation's stem. The stem of a carnation is responsible for providing support and transport of water and nutrients throughout the plant. In the experiment, the observed change could be an increase in stem length, stem thickness, or both.
The structure of a carnation's stem consists of different types of tissues with specific functions. The dermal tissues, such as the epidermis, protect the stem from external factors and prevent water loss. Vascular tissues, including the xylem and phloem, are responsible for transporting water, minerals, and sugars between the roots and leaves. Ground tissues, such as parenchyma cells, provide structural support and store nutrients.
Primary growth in stems occurs at the apical meristem, which is responsible for increasing the length of the stem. This growth is mainly due to cell division and elongation. Secondary growth, on the other hand, occurs at the lateral meristems and leads to an increase in stem thickness. This growth is mainly due to the division and differentiation of cells in the cambium layer. The origin of annual rings in stems is related to secondary growth. The cambium layer produces new xylem cells each year, and the size and density of these cells can vary depending on environmental conditions. By counting these rings, the approximate age of a tree can be determined. Modified stems are found in various plants and serve different functions. Examples include runners, which are horizontal stems that allow for vegetative propagation in strawberry plants, and bulbs, which are underground, modified stems that store nutrients and allow for vegetative reproduction in plants like onions and tulips.