Ray properties in the stems of Dahurian larch (Larix gmelinii) and Japanese larch (Larix kaempferi)

Abstract

The radial variation of rays within the stems of Dahurian larch and Japanese larch growing in Korea was studied to obtain valuable information to identify the two species and determine wood quality. Uniseriate ray height, fusiform ray height, ray number, ray spacing, and epithelial cell number were investigated by optical microscopy. The heights of uniseriate and fusiform rays and epithelial cell numbers in Dahurian larch were lower than those in Japanese larch. Dahurian larch wood had greater ray number and ray spacing than Japanese larch wood. In both species, the heights of uniseriate and fusiform rays and epithelial cell number increased with increasing growth ring number but then stabilized from a certain growth ring number. However, ray number and ray spacing decreased with age but were stable toward the bark. There were significant differences in all ray properties between the two species. Furthermore, in both species, the number and spacing of rays showed a significant negative correlation with uniseriate ray height. The relationships between uniseriate and fusiform ray height, and between ray spacing and ray number were significantly positive. In conclusion, the results from this study provide basic information that can be used to identify these species, and the quality indices from ray properties will improve the effective utilization of the two woody species.

Ray Traits of Juvenile Wood and Mature Wood: Pinus massonia and Cunninghamia lanceolata

“…For both species, the average ray numbers of juvenile wood were significantly higher than those of mature wood (p < 0.01, Table 2). This is consistent with the previous studies; the ray number in coniferous wood decreased with increasing the number of the growth ring and became a constant in mature wood [10,35,36]. The violin plot confirmed that juvenile wood of both species has higher first, median, and third quartile values than their corresponding mature wood (Figure 2e) because the largest numbers of the ray cambial initials are formed during the early juvenile years when peripheral expansion of the cambium is greatest [21].…”

“…As shown in Figure 2d, the violin plot of ray spacing presents a fluctuation around the 6/mm for Masson pine. An obvious decrease is shown in Chinese fir from juvenile wood to mature wood, in accordance with the decrease in the ray spacing of Larix gmelinii and Larix kaempferi as the growth ring number increased [10]. It should be emphasized that, according to the hypothesis proposed by Carmi et al [34] and Lev-Yadun and Aloni [12], ray spacing is controlled by excess stimuli, such as the hormone ethylene, which has a negative effect on polar auxin transport, and in turn, affects the formation of ray initials and the enlargement of existing ones.…”

“…The average ray number of juvenile wood and mature wood was 35.3/mm 2 and 28.4/mm 2 for Masson pine, 46.5/mm 2 and 41.3/mm 2 for Chinese fir, respectively. Masson pine had the similar average ray number value as Pinus koraiensis, Larix gmelinii and Larix kaempferi [10]. Chinese fir had a much higher average ray number value than Masson pine.…”

“…It should be emphasized that, according to the hypothesis proposed by Carmi et al [34] and Lev-Yadun and Aloni [12], ray spacing is controlled by excess stimuli, such as the hormone ethylene, which has a negative effect on polar auxin transport, and in turn, affects the formation of ray initials and the enlargement of existing ones. Therefore, different radial variations of the ray spacing within the stems have been observed in the published literature [10,21].…”

“…However, to date, research studying wood ray traits between juvenile wood and mature wood remains very limited [7][8][9][10]. Differences in wood ray traits between juvenile wood and mature wood is not clear.…”