How does density and nutrient stress affect allometry and fruit production in the heterocarpic species Atriplex sagittata (Chenopodiaceae)
How does density and nutrient stress affect allometry and fruit production in the heterocarpic species Atriplex sagittata (Chenopodiaceae)
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DOI：
10.1139/b99-087
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发表时间：
1999-11
期刊：
影响因子：
1.1
通讯作者：
B. Mandák;P. Pyšek
中科院分区：
文献类型：
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作者：
B. Mandák;P. Pyšek
箭叶滨藜属植物在不同密度和(或)营养条件下生长，研究了胁迫对植物异速生长的影响及特定生物计量参数的变化。密度的增加显著降低了总重、地径、茎长和分枝数。营养亏缺仅对总重和地径有负向影响，密度与养分互作均不显著。地径对总重的预测效果最好，可解释整个数据集中93.6%的变异。植株总重和地径之间的关系不受生长条件的影响，说明竞争决定了植株在描述这两个变量之间异速生长关系的直线上的位置，但似乎没有改变这种关系。但低密度下的总重与茎高、总重与分枝数之间的异速生长关系与高密度下的差异显著，说明低密度下总重的增长速度较快。分枝和植株形态都受到竞争的影响。在高密度生长的植株中，枝长随着植株总重量的增加而持续增加，但对于低密度植株，仅在茎的中段的分枝中记录到这种增加。在每种果实类型中，枝重比枝长更能准确地预测果实总重。果实产量与分枝重的异速生长关系因果实类型不同而异，A类果实产量增长快于B、C类果实，竞争对B类果实平均大小的影响小于A、C类果实，C、A类果实平均重量变异较B类果实大。单株果实总重的变异比平均果实重的变异高一个数量级。结果表明，在不同条件下生长的箭竹植株的异速生长和产生的特定果实类型的数量都发生了变化。然而，果实比例的变化是异速生长限制的函数还是异速生长的基本变化的结果，这一问题需要进一步研究。
Plants of Atriplex sagittata Borkh. were grown under different density and (or) nutrient conditions, and the effect of stress on plant allometry and variation in particular biometrical parameters was studied. Increasing density significantly reduced total weight, basal diameter, stem length, and number of branches. Nutrient deficiency had a negative effect on the total weight and basal diameter only, and the density X nutrients interactions were all nonsignificant. Basal diameter was the best predictor of the total weight, explaining 93.6% of the variation in the whole data set. The relationship between total plant weight and basal diameter was unaffected by growth conditions, indicating that competition determined the position of a plant along the line describing the allometric relationship between both variables but did not seem to alter the relationship. However, the allometric relationships between total weight and stem height and between total weight and number .of branches found at low density were significantly different from those at high density, indicating a faster increase in total weight at low densities. Branching, and consequently plant form, were affected by competition. Branch length consistently increased with total plant weight in plants grown under high density, but for low density plants, such an increase was recorded only in branches of the middle section of the stem. In each fruit type, the total weight of fruits produced was more closely predicted by branch weight than by branch length. Allometric relationships between fruit production and branch weight differed among particular fruit types, with a faster increase in the production of type A than in that of types B or C. Competition had less effect on the mean size of type B fruits compared with that of types A or C. Fruits of types C and A had higher variation in mean weight, than type B fruit. Variation in total weight of fruits per plant was of a higher order of magnitude than that in the mean fruit weight. The results show that plants of A. sagittata grown under contrasting conditions change both their allometry and the number of particular fruit types produced. Nevertheless, the question of whether the shift in the fruit ratio is a function of allometric constraints or the result of a basic shift in allometry needs further study.