OPTIMAL CONDITIONS FOR MAXIMUM MITOTIC INDEX IN ONION ROOT TIPS: INFLUENCE OF HARVESTING TIME AND ROOT AGE IN LABORATORY SETTINGS

Abstract

Utilizing the actively growing root tips of onions and sprouting lentils has become a standard practice in
science laboratories for elucidating the various stages of mitotic cell division. Though the technique is
widespread with well-established protocols, we noted inconsistencies in the distribution of cell division
stages during morning and afternoon sample preparation done for lab practical sessions. This led us to
investigate whether specific factors, such as the time of day or the age of the root, influence theprevalence
of different mitotic stages. In this study, we sought to standardize the harvesting time, and age of onion root
tips to obtain a maximum mitotic index. The roots were stained and meticulously observed three times a day
from day 1 to 9 since root induction. Concurrently, root growth parameters were also recorded. There was
no notable distinction in the mitotic index across days for both red onions and shallots. We noted a
substantial presence of mitotic stages on day 6 in red onions. Frequency of mitotic stages were
comparatively higher in the morning than afternoon and evening. Our findings indicate that the best time
for observing peak mitotic stages is during the mornings of days 5 through 7.