Sequential decline in fruit resource allocation within inflorescences of Sagittaria trifolia: a test of non-uniform pollination hypothesis
Sequential decline in fruit resource allocation within inflorescences of Sagittaria trifolia: a test of non-uniform pollination hypothesis
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三叶草花序内果实资源分配的连续下降：非均匀授粉假说的检验
DOI：
10.1111/1442-1984.12218
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发表时间：
2018-10-01
影响因子：
1.4
通讯作者：
Liao, Kuo
中科院分区：
文献类型：
--
作者：
Dai, Can;Li, Le-Na;Liao, Kuo
开花植物通常表现出花序中对花器官、果实和种子的资源投入在时间上或空间上下降。为了解释这种差异，非均匀授粉假说强调了每朵花经历的不同交配环境，为分配模式提供了适应性意义，但支持存在争议。使用慈姑（泽泻科）来检查花序内连续果实之间的种子数量、种子重量和发芽率的差异。还研究了胚珠数量以评估花期的分配模式。为了检验非均匀授粉假说，我们使用三叶草的三个多态性微卫星位点来估计近端和远端果实的种子异交率。结果表明，三叶草的种子数、平均种子重和种子发芽率在花序内由近端果向远端逐渐降低。两个相邻果实之间的种子数减少百分比为 14.68 +/- 3.22%，远强于胚珠数减少百分比 6.95 +/- 1.60%。花序内的近端和远端果实均具有较高的异交率（近端为81.5 +/- 5.0%；远端为82.3 +/- 6.9%），并且它们没有显着差异。总体而言，三叶草花序内果实的资源分配呈下降趋势。胚珠的分配模式不是种子生产的限制因素。近端果实和远端果实之间的异交率没有差异，表明分配策略可能不是由不均匀授粉引起的，而更有可能是位置效应引起的。
Flowering plants often exhibit declining resource investment to floral organs, fruits and seeds temporally or spatially in an inflorescence. To account for such variances, non-uniform pollination hypothesis, which highlights various mating environments each flower experiences, provides adaptive significance for allocation patterns but with controversial supports. Sagittaria trifolia (Alismataceae) was used to examine differences in seed number, seed weight and germination rate among sequential fruits within inflorescences. Ovule number was also investigated to evaluate allocation patterns in the floral stage. To test the non-uniform pollination hypothesis, we used three polymorphic microsatellite loci of S. trifolia to estimate the seed outcrossing rate in proximal and distal fruits. The results showed that the seed number, average seed weight and seed germination rate of S. trifolia gradually decreased from proximal to distal fruits within inflorescences. The percent of decrease in seed number between two contiguous fruits was 14.68 +/- 3.22%, which was much stronger than the percent of decrease in ovule number at 6.95 +/- 1.60%. Both proximal and distal fruits within inflorescences had high outcrossing rates (81.5 +/- 5.0%, proximal; 82.3 +/- 6.9%, distal) and they did not differ significantly. Overall, there was an acropetal decline of resource allocation to fruits within inflorescences of S. trifolia. Allocation pattern to ovules was not a limiting factor for seed production. The lack of difference in outcrossing rate between proximal and distal fruits indicated that the allocation strategy was probably not caused by non-uniform pollination, but more likely position effects.