环剥对红松(Pinus koraiensis)韧皮部和木质部碳水化合物的影响

树干环剥可以阻碍韧皮部光合产物的运输并进一步影响光合产物的分配。长时期内,环剥能够导致环痕上部可溶性糖和淀粉的积累,但对于短期内如何影响碳水化合物在木质部和韧皮部内的运输模式所知甚少。以38年生红松(Pinus koraiensis Sieb.etZucc.)为研究材料,分别对环剥上部、下部每隔1~2d采样,区分木质部和韧皮部(树皮)进行可溶性糖和淀粉含量及树干糖呼吸消耗速率测定,确定环剥后的日变化和周变化,并对木质部可溶性糖、淀粉含量与韧皮部中相应指标进行相关关系的回归分析。结果发现:(1)环剥后4周内,在环剥痕上、下部间木质部可溶性糖和淀粉含量,韧皮部中淀粉含量均不存在显著差异(p>0.05),而韧皮部内可溶性糖含量,环剥后第2周出现显著差异,从第4周出现环剥上部显著高于下部的碳水化合物积累现象(p<0.05);(2)环剥阻隔了韧皮部可溶性糖的纵向运输,但是并不影响木质部的纵向运输,而且环剥并没有影响木质部和韧皮部之间的糖和淀粉的相关关系;(3)环剥第1周内环剥上部和下部呼吸消耗速率差异不显著,第2周环剥上部显著高于环剥下部,从第3周开始环剥下部呼吸消耗速率显著下降。推断认为,在环剥处理的4周内,环剥上部冠层新形成的碳水化合物很大一部分均被呼吸消耗掉,导致环剥上部较环剥下部可溶性糖稍有增加;红松胸高直径以下部分所储藏的碳水化合物足以保障2周内红松树干呼吸。

Effects of girdling on carbohydrates in the xylem wood and phloem bark of Korean pine (Pinus koraiensis)

Stem girdling treatment inhibits the axial transport of carbohydrates through the phloem and affects resource allocation to different organs of trees.Previous studies indicated that starch and soluble sugar may accumulate in the upper part but diminish in the lower part of the girdled stem in the long run.However,few studies so far have examined the short-term dynamics of starch and soluble sugar after the girdling and this information is important for understanding the functioning of carbohydrates for plant growth.For example,how much time does it take for girdling treatment to induce the accumulation or reduction of different carbohydrates and does girdling treatment affect the phloem-xylem transport of sugars? How are the dynamics of carbohydrate reserves related to the respiratory consumption in stem? To answer these questions,we carried out a stem girdling study on trees of Korean pine(Pinus koraiensis Sieb.et Zucc.)(38-year-old).We measured respiratory consumption of sugars with a Li-6400 system at an interval of 1-2 days.We collected samples of xylem woods and phloem barks at the same interval for carbohydrate analysis with the colorimetric method(Anthrone-perchloric acid method).We found:(1)During the 4 weeks of measurement,soluble sugar and starch in xylem and starch in phloem in the upper part of the girdled stems did not differ from those in the lower part(p>0.05).(2)Differences in soluble sugar in phloem between the upper and lower parts were first observed in the second week and substantially higher values in the upper part were observed during the 4th week(p<0.05).(3)Girdling treatment obstructed the axial transport of soluble sugar via phloem but did not affect the transport in xylem.Moreover,girdling treatment did not affect the correlation of soluble sugar between phloem and xylem.(4)Girdling treatment strongly affected the respiratory consumption of carbohydrates in stems.During the first week,the sugar consumption rate in the upper part did not differ from that in the lower part(p>0.05).However,the consumption rate in the upper part of the girdled stem sharply increased in the second week and became significantly higher than that in the lower part(p<0.05).From the third week,the consumption rate in the lower part significantly decreased(p<0.05).We conclude that the most recently formed carbohydrates from canopy leaves were consumed by the enhanced respiration sincewe observed only slight increase in soluble sugar and no change in starch in the upper part of the girdled stems.Moreover,the stored carbohyrates could supply substrates about 2 weeks for the high respiration in the lower part of the girlded stems.