顕微分光測光法によるスギ心材形成過程の観察

Abstract

スギ立木から11月に採取した白線帯と心材部分について, 切片の作製法や測光法に検討を加えることにより, 放射および軸方向の柔細胞に保有されている内容物や, 仮道管内腔に見られる油滴状物質の分光測光を可能とした。そして, 白線帯の放射柔細胞の液胞や仮道管内腔の油滴状物質中に, 心材成分もしくはその前駆物質の生成を示すと考えられる紫外域の吸収が検出された。そしてこれらが濃く着色するにつれて, 吸収極大が長波長側へとシフトすることが明らかとなった。一方, 無染色切片の紫外域探査の困難さを軽減するために染色法が顕微分光測光法に導入され, これによって心材化に伴う油滴状物質中の脂質の減少を検出することができた。

Heartwood formation was investigated in SUGI (Cryptomeria japonica) by an UV-VIS microscopic spectrophotometry. It is a very severe problem in spectroscopic detection of heartwood substances and its precursors to prevent the influence of lignin contained in cell walls which has strong UV absorption, because these substances are generally enclosed with cell walls. In order to analyze the distribution of these substance, in white zone and outer part of heartwood without the lignin affection, sections were chosen to survey only the cell lumen (Fig. 1), and also photometric condition under the non-parallel illumination was examined (Figs.2, 3). Colored substances in the heartwood were measured in UV-VIS region, maximum absorption was shown to be shifted from 290 nm to 360 nm according to the density (Fig. 4). The UV spectrums of colorless vacuoles of ray parenchyma cells and droplet-like structure in tracheid lumens were measured, and some maximum absorption at around 275-300 nm were obtained (Fig. 5). Precursors of heartwood substances were supposed to be transferred from ray cells to tracheid lumens. Stained-sections with Nile blue were applied to UV-VIS spectrophotometry for the coordination between the staining method and spectrophotometry (Fig. 6). Some modifications in droplet-like structures are suggested by the decrease of absorption at 540-545 nm.