Chloroxylon swietenia DC. (Rutaceae) is widely used in folk medicine and provides a commercial timber. In the present study, phenological events such as flowering and fruiting phenology, pollinator visitation, anthesis, pollen viability, and pollen tube germination tests were analyzed in 11 populations, in Tamil Nadu, India. The number of flowers was recorded as 82.6 ± 1.4 to 162.2 ± 4.2 during flower bud formation and reduced to 25.4 ± 0.5 to 61.8 ± 1.0 at maturity. The number of fruits per twig was 21.0 ± 0.8 to 47.2 ± 0.7 in initial stages and slightly reduced to 16.2 ± 1.8 to 34.6 ± 1.4 at maturation. Sixty-two species of insects were visiting the flowers with bees/ants as effective pollinators. The 2,5-diphenyltetrazolium bromide assay revealed more viable pollen grains in five populations, and fluorescence dye assay revealed maximum viable pollen grains in six populations. In the pollen tube germination test, the 60% sucrose concentration provides significant results, with a high number of germinated pollen grains. Principal component analysis of flowering and fruiting phenology, floral visitors, and pollen viability showed 79.5%, 79.3%, 56.7%, and 41.7% for the first factor, respectively. Our results indicated that C. swietenia depends heavily on pollinators for its reproduction. Hence, there is a need to expand this study to related species which are having agronomic, pharmacological, and economic potential.
Anthropogenic growth in Earth's climate is affecting many aspects of ecological systems (Traill et al 2010), including seasonal timing of biological events, which includes leaf, flowering, and fruiting phenology. Association between phenology and reproductive events in plants with diverse climatic conditions has been well understood; mainly, flowering phenology has a major impact on plant reproductive biology, and its success concerns evolutionary and ecological consequences (Tadey 2020). Flowering phenology is driven by climatic conditions, and this enables the plants to bloom when the surrounding climatic features are most suitable, ensuring effective sexual reproduction (Theobald et al 2017). The importance of phenology to the science of global change has been progressively renowned during the last few decades (Schwartz 1998; Fitter and Fitter 2002; Tandon et al 2003; Selwyn and Parthasarathy 2006; Singhal et al 2011; Tadey 2020).
Pollination biology is a prime process in plant reproductive achievement, frequency, and identity of floral visitors, the ability for autonomous self-pollination, and the magnitude of pollen limitation, in which pollinators transmit vital ecosystem facilities to diverse ecosystems such as natural ecosystems and agroecosystems (Tandon et al 2003; Aizen and Harder 2007; Tadey 2015; Richardson et al 2017; Figueiredo et al 2020; Impe et al 2020). Diversity of wildflowers is maintained by pollination, and it plays an important role in resolving floral resource–related problems such as herbivores and seed predators (Potts et al 2006). Most of the plants depend on animal pollination for their sexual reproduction via insects, birds, bats, and so on, among which insects play a vital role in pollination. It is well accepted that diversity of pollinators or the number of interactions established by a specific plant is defined by different features, for example, resource availability (quantity of nectar or pollen), morphological traits such as color, size, and shape of flowers, and flowering time (Bosch et al 1997); significant association was found between flower color and flowering phenology (Warren and Billington 2005).