# Comparison of Biochemical Constituents and Contents in Floral Next of _Castanae_ spp.
## 3 Discussion  
In this study, we have analyzed the volume of secreted nectar, free sugar composition, amino acid content, and composition of VOCs in floral nectar obtained from _Castanae_ spp. to evaluate the value of the honey source. The nectar volume and nectar concentration affect the feeding behavior of pollinators [20; 21; 22]. In this study, significant differences in nectar volume (8.7-42.7 \(\mu\)L/catkin) and nectar concentration (22.8-61.8 Brix) were observed among the _Castanae_ spp. (Table 1). Given that honey bees can collect nectar with a concentration of 15 to 60 Brix, the chestnut nectar is considered positive for honey bees [23]. According to [PERSON] and [PERSON] [24] that are differences in the nectar volume in the same species depending on the tree's age, the location of flowers, the size of flowers, and environmental factors. Also, there was a difference in nectar volume according to soil type and moisture content [25]. In this study, the environmental variation was minimized by planting each species in the same location. It was determined that there was a difference in the nectar volume by chestnut species. A previous study was reported that there was a significant difference in the nectar volume and sugar concentration between Korea hawthorn (1.4 \(\mu\)L, 27.2 Brix) and Chinese hawthorn varieties (3.6-5.4 \(\mu\)L, 11.3-12.6 Brix) [26]. The result of investigating the nectar properties of four varieties of the _C. crenata_ showed that nectar volume (6.7-54.3 \(\mu\)L) and nectar concentration (18.2-57.1 Brix) displayed significant difference among the varieties, showing the same trend as in this study. Because the dietary sugar consumed by bees affects the amount of honey available to humans through digestive physiology, sugar analysis is required for study of honey plants [26; 27]. In this study, the sugar content (22.6-82.5 \(\mu\)g) and sugar content per catkin (0.43-1.35 mg/catkin) of floral nectar showed a significant difference (Table 1, \(p\) = 0.000). A previous study suggested that the sugar content per flower calculated by using the nectar volume and free sugar content rather than the nectar volume affected by meteorological factors should be the main factor for investigation or individual selection of honey plants [28]. Free sugar content was highest in CMC, but sugar content per catkin considering the amount of nectar volume was highest in CCJ. As a result of analyzing the free sugar content of four chestnut varieties [27], the free sugar content (16.4 to 69.3 \(\mu\)g) and the sugar content per catkin (0.48 to 1.40 mg/catkin) displayed significant differences, which showed the same results as our study. However, a previous study comparing nectar characteristics between Korean and Chinese Hawthorn reported that the nectar volume and the free sugar content significantly differ, but the nectar sugar contents per flower of Korean hawthorn (69.2 \(\mu\)g) and Chinese hawthorn varieties (50.6-79.0 \(\mu\)g) did not significantly differ [26]. Therefore, it is judged that nectar characteristics such as the nectar volume, nectar concentration, and sugar content per catkin vary greatly depending on the species or varieties. The sugar composition, such as the sucrose/hexose ratio (S/H ratio), affects the diet of pollinators [7; 20]. According to the previous study [20], S/H ratio were classified into four grades; sucrose dominant (ratio \(>\) 1.0), sucrose rich (0.5-1.0), hexose rich (0.1-0.5), and hexose dominant (ratio \(<\) 0.1). In this study, the S/H ratio in the floral nectar of _Castanae_ spp. ranged from 0.02-0.07 and showed hexose rich or hexose dominant grades (Table 1). [PERSON] et al. [29] reported that the sucrose content in floral nectar of male and female _Evodia daniellii_ Hmsl (Korean evodia tree) was 71.4% and 52.8%, respectively, and the S/H ratio was 2.5 and 1.2. Considering that the S/H ratio showed 0.6 in hawthorn and 0.2-0.7 in _Tilia insularis_ Nakai (linden), it was found that chestnut nectar has a significantly lower S/H ratio [26; 28].