Introduction:
Plant physiology is a branch of botany that deals with the study of the functioning and processes of plants. It is an important subject for the Botany optional in the UPSC exam. To improve your understanding of plant physiology, you can follow the below steps:

1. Study the basics:
Start by studying the basics of plant physiology, including the structure and functions of different parts of a plant such as roots, stems, leaves, and flowers. Understand the processes of photosynthesis, respiration, transpiration, and reproduction in plants.

2. Read textbooks:
Refer to standard textbooks on plant physiology like "Plant Physiology" by Taiz and Zeiger, "Plant Physiology and Development" by Lincoln Taiz and Eduardo Zeiger, or "Plant Physiology" by Frank B. Salisbury and Cleon W. Ross. These textbooks provide comprehensive information on various topics of plant physiology.

3. Take notes:
Make concise notes while studying. Summarize the important points and concepts in your own words. This will help you retain and recall the information easily.

4. Use visual aids:
Utilize diagrams, flowcharts, and illustrations to understand complex processes and concepts. Visual aids can help in better comprehension and retention of information.

5. Practice with diagrams:
Draw and label diagrams of important physiological processes like photosynthesis, respiration, and transpiration. This will help you understand the sequence of events and the structures involved.

6. Solve practice questions:
Solve practice questions from previous year question papers and mock tests. This will help you evaluate your understanding and identify areas that need improvement.

7. Discuss with peers:
Engage in group discussions with fellow aspirants or join online forums to exchange ideas and clarify doubts. Discussing concepts with peers can provide different perspectives and deepen your understanding.

8. Refer to online resources:
There are several online resources available for studying plant physiology. Websites like EduRev offer free study materials, notes, and video lectures on various topics of plant physiology. Utilize these resources to supplement your learning.

9. Revise regularly:
Regular revision is crucial to reinforce your understanding of plant physiology. Set aside dedicated time for revision and go through your notes and important concepts at regular intervals.

10. Seek guidance:
If you find certain topics challenging, seek guidance from teachers or subject matter experts. They can provide additional explanations and clarify your doubts.

Conclusion:
Improving your understanding of plant physiology for the Botany optional subject requires a systematic approach. By studying the basics, referring to textbooks, using visual aids, practicing with diagrams, solving practice questions, discussing with peers, utilizing online resources, regular revision, and seeking guidance when needed, you can enhance your knowledge and perform well in the UPSC exam.