CO_2浓度加倍对辽东栎维管组织结构的影响

EFFECTS OF DOUBLED CO_2 CONCENTRATION ON STRUCTURE OF V ASCULAR TISSUES OF QUERCUS LIAOTUNGENSIS

以辽东栎 (Quercus liaotungensis)的 13年生幼树为材料 ,分别培养在大气 CO2 浓度加倍 (70 0μl· L- 1 )与对照 (35 0 μl· L- 1 )的开顶式熏气室中 ,研究 CO2 浓度升高对其茎次生木质部和次生韧皮部结构的影响。结果表明 :经 CO2 浓度加倍处理的两个生长季内 ,辽东栎的年轮宽度明显增加 ,为对照的 30 0 %～ 370 % ,其中晚材宽度的增加更为显著 ,为对照的 75 0 %～ 830 %。另外 ,晚材中导管的密度和径向直径分别比对照增加 5 0 %和 2 0 % ;木纤维细胞的比例约为对照的 170 %。但早材的导管分子和木纤维细胞与对照相比均无显著变化。在 CO2 浓度加倍条件下 ,辽东栎的次生韧皮部中含晶韧皮薄壁细胞的数目 ,每条韧皮纤维切向带中韧皮纤维细胞的数目 ,以及韧皮纤维长度均有显著增加 (p≤ 0 .0 5 )。相反地 ,韧皮纤维细胞的直径和筛管分子长度却无明显变化。值得提出的是 ,在 CO2 浓度加倍的条件下 ,次生韧皮部的宽度、筛管分子的直径、以及每年形成的韧皮部细胞总数分别为对照的 82 %、87%和 80 %。综上所述 ,大气 CO2 浓度加倍对辽东栎次生木质部的生长发育具明显的正效应 。

The structure of secondary xylem and secondary phloem of Quercus liaotungensis grown under conditions of amb ient (350 μl·L -1 ) and doubled CO 2 concentration (700 μl·L -1 ) was investigated. Statistical analysis of results indicated that ring width inc reased significantly under the CO 2-enriched environment, which was 300%-370% of those from plants grown under ambient CO 2 environment (CK). In particular, latewood width was affected much more strongly by the treatment. Furthermore, ve ssel number per square millimeter and radial diameter of vessels of latewood as well as ratio of wood fibers also increased, 150%, 120% and 150% respectively o f that observed under CK. Nevertheless, no dramatic change was observed in term s of mean length and tangential diameter of vessels, thickness of cell wall and length of fibers of secondary xylem. In the secondary phloem, mean length and nu mber of phloem fibers and crystalliferous parenchyma cells per phloem fiber band increased in response to higher CO 2 (p≤0 05). In contrast, width and to tal cells of seondary phloem formed each year and diameter of sieve tubes were r educed to 82%, 80% and 87% of that of the CK grown plants respectively with incr eased CO 2 concentration. It was concluded that secondary xylem responded posi tively, while the diameter of sieve tubes and the width of secondary phloem sho wed a negative response to CO 2-enrichment during the experiment.