Department of Biology, Lewis and Clark College, Portland, Oregon 97219 USA.
Am J Bot. 2000 Dec;87(12):1765-8.
To determine whether unfertilized ovules continue to grow when in an ovary containing fertilized ovules, we measured ovule lengths in developing fruits of Epilobium obcordatum that were harvested 4, 5, 8, and 10 d post pollination. We found that unfertilized ovules that were in the presence of fertilized ovules continued to grow and that there was a broad range of overlap in their sizes at all sampling times. This effect was found for two types of unfertilized ovules that occur throughout the length of the ovary: normal, unfertilized ovules, apparently bypassed by pollen tubes; and sterile ovules lacking an embryo sac. In addition, there is a position effect within developing fruits. Both fertilized and unfertilized ovules are larger at the stylar end. In six samples resulting from pollination with a single pollen tetrad, a total of 18 embryos were found, and the effect on unfertilized ovules, greatest at the stylar end, diminished with distance from the ovules with embryos. Our results are consistent with the interpretation that diffusible hormones produced by developing seeds cause nearby unfertilized ovules to grow. We conclude that caution is necessary when attempting to infer ovule fertilization histories from the appearances of ovules in developing and mature fruits. What are often inferred to be aborted seeds, in many cases, may not be seeds at all. They may be enlarged, unfertilized ovules.
为了确定含有受精胚珠的卵巢中未受精胚珠是否继续生长，我们测量了授粉后 4、5、8 和 10 天收获的柳叶菜属植物发育果实中的胚珠长度。我们发现，存在受精胚珠的未受精胚珠继续生长，并且在所有采样时间，它们的大小都有很大的重叠。这种效应在卵巢全长范围内存在两种类型的未受精胚珠中都有发现：正常的、未受精的胚珠，显然被花粉管绕过；以及缺乏胚囊的不育胚珠。此外，在发育中的果实中还存在位置效应。受精和未受精的胚珠在花柱端都较大。在由单个花粉四分体授粉的六个样本中，总共发现了 18 个胚胎，并且未受精胚珠的这种效应在花柱端最大，随着与具有胚胎的胚珠的距离增加而减小。我们的结果与这样的解释一致，即由发育中的种子产生的可扩散激素导致附近的未受精胚珠生长。我们得出的结论是，在试图从发育中和成熟果实中的胚珠外观推断胚珠受精历史时，需要谨慎。在许多情况下，被推断为败育种子的，可能根本不是种子，而是增大的、未受精的胚珠。
