There are several research papers and journals that can be referred to for the UPSC Botany optional subject exam. Here are some of them:

1. "Indian Botanical Society Journal" - This journal covers a wide range of topics related to botany, including plant taxonomy, ecology, biotechnology, and conservation. It publishes original research papers, review articles, and book reviews.

2. "Journal of Plant Sciences" - This journal focuses on fundamental and applied research in all aspects of plant biology. It covers topics such as plant physiology, genetics, molecular biology, and ecology. It publishes both research articles and reviews.

3. "Botanical Journal of the Linnean Society" - This journal publishes original research articles in all areas of botany, including plant systematics, evolution, ecology, and conservation. It also publishes reviews, perspectives, and book reviews.

4. "Journal of Plant Research" - This journal publishes research papers, reviews, and short communications in all areas of plant biology. It covers topics such as plant physiology, biochemistry, genetics, ecology, and molecular biology.

5. "International Journal of Plant Sciences" - This journal publishes original research articles and reviews in all areas of plant biology, including plant morphology, anatomy, physiology, ecology, and evolution. It welcomes interdisciplinary research and publishes studies on both terrestrial and aquatic plants.

6. "Current Science" - Although not exclusively focused on botany, this interdisciplinary journal covers a wide range of scientific disciplines, including plant sciences. It publishes research articles, reviews, and perspectives in various areas of science, including botany.

It is important to note that while these research papers and journals can provide valuable information and insights into the field of botany, they should be used as supplementary resources alongside standard textbooks and reference books recommended for the UPSC Botany optional subject exam.