指数施肥对楸树无性系生物量分配和根系形态的影响

为探求楸树不同无性系生物量分配和根系形态的差异,2011年3-8月在甘肃省天水市小陇山林科所,以2年生楸树无性系1-4、7080和015-1组培苗为试验材料,设置了CK、6、10、14 g尿素/株4个处理,研究指数施肥对楸树无性系生物量分配和根系形态的影响.结果表明:(1)同一无性系中,10 g尿素/株的根、茎、叶生物量及总生物量、根长、根表面积、根体积和根平均直径均高于其它处理.无性系015-1的生物量和根系形态参数整体上高于无性系1-4和7080.无性系015-1在10 g尿素/株的根、茎、叶生物量及总生物量分别为89.44 g、61.30 g、79.97 g、230.71 g,是CK的1.48、1.52、2.09、1.66倍;根长、根表面积和根体积为22667 cm、6260 cm2、578.14 cm3,是CK的1.94、1.54、2.43倍.(2)指数施肥和无性系的遗传差异明显影响楸树不同无性系生物量的分配格局.适量施氮明显促进3个楸树无性系生物量的积累,而氮素缺乏或过量均不利于生物量的积累.8月同一无性系的根冠比均随施氮量的增加而降低;同一处理下无性系7080的根冠比高于无性系1-4和015-l.无性系1-4和7080的生物量主要向叶和茎分配,而无性系015-1主要向叶分配.(3)指数施肥在6月和7月主要促进细根根长和根表面积的增加;指数施肥在8月主要促进细根、中等根和粗根体积的急剧增加,分别比7月高达36.88％、124.96％、154.79％.这利于根系在中后期吸收更多养分,从而引起生物量分配格局的变化.(4)生物量参数和根系形态参数关系密切.根生物量、地上生物量、总生物量分别和根长、根表面积、根体积、根平均直径极显著正相关;根冠比和根长、根表面积、根体积、根平均直径极显著负相关;比根长和地上生物量、总生物量显著正相关,和根冠比极显著负相关.

Effects of exponential fertilization on biomass allocation and root morphology of Catalpa bungei clones

In order to study the differences of Catalpa bungei clones' biomass allocation and root morphology, an exponential fertilization trial was conducted with three nitrogen dose levels of 6 10, 14 g urea per plant and CK. The experimental materials were two-year Catalpa bungei clones 1-4, 7080 and 015-1 tissue culture-seedlings. We conducted the experiment in Xiaolongshan forestry science and technology research institute, Tianshui city, Gansu province from March to August 2011. The results showed that: (1) After the end of the fertilization, the root biomass, stem biomass, leaf biomass, total biomass, root length, root surface area, volume of root and root average diameter with 10 g urea per plant treatment were higher than other treatments in the same clone. The clone 015-1 showed higher values of biomass parameters and root morphological parameters than the clone 1-4 and clone 7080. The root biomass, stem biomass, leaf biomass and total biomass of clone 015-1 with 10 g urea per plant treatment were 89.44 g, 61.30 g, 79.97 g, 230.71 g, which were 1.48, 1.52, 2.09, 1.66 times that with CK. The root length, root surface area and volume of root of the same treatment were 22667 cm, 6260 cm², 578.14 cm³, and 1.94, 1.54, 2.43 times that with CK respectively. (2) Exponential fertilization and genetic differences of the clones significantly affected three Catalpa bungei clones' biomass allocation pattern. The application of nitrogen exponential fertilization significantly promoted the root biomass, stem biomass, leaf biomass and total biomass accumulation of three Catalpa bungei clones, while nitrogen deficiency or excess showed negative effects to the accumulation of biomass. In August the root to shoot ratio of the same clone decreased with the increase of the amount of nitrogen. For the same treatment, the clone7080 showed higher ratio than the clone 1-4 and clone 015-1. The biomass of the clone 1-4 and clone 7080 were mainly allocated to leaves and stems, while the clone 015-1 to leaves. (3) Exponential fertilization in June and July increased three Catalpa bungei clones' fine root lengths and surface areas, accounting for the proportion of the whole plant'root length and root surface area up to 96.99%, 86.82%, 93.10%, 72.52%. Exponential fertilization mainly increased three Catalpa bungei clones' volumes of roots. The fine roots, roots, and coarse roots in August increased by 36.88%, 124.96%, and 154.79% compared with those in July. This helped the roots intake more nutrients in the late of exponential fertilization, thus would affected the changes in the pattern of biomass allocation of three Catalpa bungei clones. (4) The biomass parameters and root morphological parameters of three Catalpa bungei clones were closely related. After the end of the fertilization, the root biomass, aboveground biomass and total biomass were extremely positively related to root length, root surface area, root volume and root average diameter. The root-shoot ratio was significantly negatively correlated with root length, root surface area, root volume, root average diameter. The specific root length was significantly positively correlated with aboveground biomass, total biomass and significantly negatively correlated with root-shoot ratio.