研究了河南省商丘市2年生泡桐一个生长季节的养分变化情况及不同冠层养分状况。结果表明:在自然状况下,从出叶到落叶的整个生长过程中:①N元素的浓度是呈锯齿状下降趋势,最高值出现在5月末,为42.0g·kg-1,最低值出现在11月中旬,为21.5g·kg-1;P元素浓度是在生长季开始时较高,最高为2.5g·kg-1,到6月份以后基本趋于平稳,到10月份,又呈现下降趋势直到落叶,最低为1.2g·kg-1;K元素浓度在生长季开始时较高,最高为14g·kg-1,到6月份以后基本趋于平稳,直到9月底。10月份呈现下降趋势,从11月开始又基本稳定直到落叶,最低值为6.6g·kg-1;②整株树的养分积累状况中,N、P、K三种元素呈现出相似的变化规律,在开始略有下降,随后是一直增长,到7月份达到最高,N、P、K最高积累量分别为7.26g·株-1、0.37g·株-1、2.3g·株-1,之后开始下降,到9月份降到最低,N、P、K最低积累量分别为3.2g·株-1、0.16g·株-1、0.96g·株-1,随后又开始缓慢增长,直至落叶;③单叶片的营养元素的积累量是持续增长的;④不同冠层的N、P、K浓度差异不显著。

采用L i-6400光合分析系统, 对修枝接干和对照泡桐不同冠层、不同方位叶片在不同光量子密度条件下的净光合速率( Pn )进行测定, 并采用经验方程对其光反应曲线进行拟合, 结果表明: ( 1) 修枝接干可明显提高泡桐植株总体的光合潜力和适应强光环境的能力, 其最大光合速率( Pmax ) 、光饱和点( LSP)、光补偿点( LCP) 和光合幅度( PR)在修枝后分别达23. 93 μmol·m-2·s-1、1 966. 58 μmol·m-2·s-1, 53. 88 μmol·m-2·s-1、1 911. 71 μmol·m-2·s-1, 较对照分别高11. 85% 、15. 61%、29. 06%、15. 21%。( 2)修枝接干对泡桐诸光合指标的影响在树冠下层明显大于上层, 并且使其上下冠层之间的差异性显著减小。修枝后泡桐下层树冠的Pmax、LSP、LCP、PR较对照分别高27. 70%、36. 74%、34. 22%、36. 80%, 而上层差异不显著。( 3)修枝接干对处于不同方位泡桐叶片的光合特性的影响在不同冠层具有不同程度的体现。在树冠上层的阳位与阴位间, 修枝接干后的Pma x、LSP、LCP和PR 分别较对照有所提高, 但均不显著; 而在树冠下层, 修枝接干后其阳位叶的Pmax、LSP、LCP 和PR 分别较对照高21. 80%、39. 02%、28. 72%和39. 26%, 阴位叶分别较对照高42. 18%、39. 35%、48. 70% 和39. 13%, 除了LCP在二处理间阳位的差异不显著外, 其余的差异性均显著。

With the method of long-term experiment and statistical analysis,time variation of leaf traits and their correlations in a whole growth season were studied.The result showed that:(1) leaf area increased with growth time prolonging and the curve took on S pattern.Its relationship could be described with y=e(5.528 93-5.104/x).The specific leaf weight increased with growth time prolonging and its model was cubic y=0.000 002 x3-0.000 8 x2+0.088 1 x+2.942 1.Leaf water content in the growth season increased in the model y=-0.000 1 x3+0.031 9 x2-3.616 3 x+424.56.Season dynamics of leaf fresh weight in the growth season was S pattern and its model was y=e(1.770 8﹣36.299/x).Leaf dry weight was y=0.042 5 x0.6971 .Dry / fresh ratio was y = 0.000 000 009x3-0.002 6 x2+0.262 x+16.946.(2) a significant positive correlation existed between leaf dry weight and leaf area.Their relationship could be described with y=0.008 1 x﹣0.253 6.Relation of leaf fresh weight and leaf area was significant positive correlation and its model was y=0.020 7 x1.0203.Leaf dry weight and leaf water content was significant negative correlation and its model was y=7.710 6e﹣0.002 7 x.With the method of municipal statistical analysis,it confirmed that the relation among the leaf dry weight,leaf area,leaf water content,specific leaf weight,dry / fresh ratio was y(leaf dry weight)=0.006 6 x1(leaf area)+0.003 22 x2(leaf water content)+0.187 95 x3(specific leaf weight)+0.035 27 x4(dry/fresh ratio)-3.071 2.(3) it proved that season variation of paulownia leaf modal traits closely related to the local climate.The other traits and their mechanisms needed further study.