Protoplasmic streaming movements are referred to as

The correct option is autonomic movements of locomotion.

To understand why this is the correct answer, let us break down the concepts involved step-by-step:

1. What is protoplasmic streaming?
Protoplasmic streaming, also known as cyclosis, is the directed flow of the fluid substance (cytoplasm) inside a living cell. This movement facilitates the transport of nutrients, proteins, and organelles within the cell, and in some single-celled organisms, it is directly responsible for whole-cell movement (locomotion).

2. Autonomic vs. Induced movements:
In plant physiology, movements that occur spontaneously due to internal factors (intrinsic stimuli) without any external environmental influence are termed autonomic (or spontaneous) movements. Since protoplasmic streaming is driven by internal cellular mechanisms (such as the interaction of actin filaments and myosin motor proteins utilizing ATP), it is classified as an autonomic movement.

3. Movements of Locomotion vs. Movements of Curvature:
Movements of curvature involve the bending of plant organs (like stems or roots) in response to a stimulus, without the translocation of the entire organism or cell. On the other hand, movements of locomotion involve the movement of the entire cell, organism, or its internal protoplasm from one place to another. Because protoplasmic streaming involves the active flow and displacement of the cellular fluid, it is categorized as a movement of locomotion.

4. Evaluating the other options:
- Photonasty and thigmonasty are types of nastic movements (movements of curvature) that are induced by external stimuli (light and touch, respectively). They are not autonomic, nor are they movements of locomotion.
- Movements of curvature refer to bending growth or turgor changes in multicellular structures rather than the internal fluid movement of single cells.

Therefore, protoplasmic streaming movements are correctly referred to as autonomic movements of locomotion.