Ask Dr. Biology Answers Your Plant Vacuole Question!!

Hey Class! We have our plant vacuole answer from ask Dr. Biology! Here it is! Hi Rebecca, Thank you so much for your patience! The size of the vacuole depends mainly on the size of the cell, and the larger the cell the larger the vacuole. Cacti, succulents and cells modified for storage (roots, fruits) tend to be very large, and therefore have huge vacuoles. Small cells like those of the epidermis that don't store materials have very small vacuoles. One of the main functions of the vacuole is to help increase cell size by creating a positive pressure on the cell wall during cell development. Developmentally the vacuole is relatively large early in the life of a cell (some authors state up to 90% of a typical cell), but depending on the function of that cell at maturity its relative proportions change. In cells modified for storage like those of a potato or apple will continue to have large vacuoles (~90%) where cells modified for photosynthesis like the palisade mesophyll of leaves the vacuole is much smaller (easily under 50%, some authors say around 30%). I hope this helps to explain this question and it might be fun to make a few cross sections of various leaves, roots and stems to explore this question. A very small piece of macerated pear flesh will provide some very large cells that are almost entirely vacuolate and some small cells (the grit of a pear) that are dead at maturity and no longer contain vacuoles. I hope that answers your question! John Benedict (answering for ASU's Ask A Biologist) PhD student of biology Arizona State University