Study on Sex Determination and Variation in Gender Expression of Individual Trees in a Population of Cedrus deodara (Roxb.) G. Don. From Dense Temperate Forests of Northern India

Abstract

Conifers are reported to exhibit predominantly monoecious behaviour however, numerous species and some genera show uncertainties regarding their gender expression. The factors influencing the sexual differentiation of strobili in monoecious or dioecious conifers remain poorly understood. To investigate this unpredictable phenomenon in conifers, we selected three populations representing pure stands of Cedrus deodara in dense temperate forests of Northern India, specifically one in Uttarakhand and two in Himachal Pradesh. Each site was surveyed, and total 900 trees were marked as male, female, monoecious and neutral trees based on their reproductive behaviour and sexual representation. Selection criteria were based on the reproductive age of Cedrus deodara, as it attains maturity when it reaches a height of 19 to 20 meters. Our findings revealed that Cedrus deodara exhibits subdioecious behaviour, characterized by the occurrence of four basic sex forms such as male trees, female trees, monoecious trees, and neutral trees. Yearly observations from 2014 to 2016 unveiled that Cedrus deodara does not exhibit consistent reproductive behaviour. Instead, the species displays a fascinating pattern of alternation between dioecy and monoecy. Additionally, it was also found that individual trees demonstrated change in their expression of sex during each reproductive cycle. These findings underscore the complexity of sex determination and reproductive plasticity in Cedrus deodara. The study has revealed that the monoecious behaviour was more dominant than the dioecious behaviour, and the individual tree changes its sexual representation depending upon the rate of seed production the previous year. This research pave the way for future investigations into the factors influencing sex expression and reproductive behaviour in conifers and will contribute to our broader knowledge of plant sexuality and plant evolution.