Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, 80309, USA.
Ann Bot. 2010 Aug;106(2):309-19. doi: 10.1093/aob/mcq110. Epub 2010 Jun 2.
Variability in embryo development can influence the rate of seed maturation and seed size, which may have an impact on offspring fitness. While it is expected that embryo development will be under maternal control, more controversial hypotheses suggest that the pollen donor and the embryo itself may influence development. These latter possibilities are, however, poorly studied. Characteristics of 10-d-old embryos and seeds of wild radish (Raphanus sativus) were examined to address: (a) the effects of maternal plant and pollen donor on development; (b) the effects of earlier reproductive events (pollen tube growth and fertilization) on embryos and seeds, and the influence of embryo size on mature seed mass; (c) the effect of water stress on embryos and seeds; (d) the effect of stress on correlations of embryo and seed characteristics with earlier and later reproductive events and stages; and (e) changes in maternal and paternal effects on embryo and seed characteristics during development.
Eight maternal plants (two each from four families) and four pollen donors were crossed and developing gynoecia were collected at 10 d post-pollination. Half of the maternal plants experienced water stress. Characteristics of embryos and seeds were summarized and also compared with earlier and later developmental stages.
In addition to the expected effects of the maternal plants, all embryo characters differed among pollen donors. Paternal effects varied over time, suggesting that there are windows of opportunity for pollen donors to influence embryo development. Water-stress treatment altered embryo characteristics; embryos were smaller and less developed. In addition, correlations of embryo characteristics with earlier and later stages changed dramatically with water stress.
The expected maternal effects on embryo development were observed, but there was also evidence for an early paternal role. The relative effects of these controls may change over time. Thus, there may be times in development when selection on the maternal, paternal or embryo contributions to development are more and less likely.
胚胎发育的变异性会影响种子成熟和种子大小的速度，这可能会对后代的适应性产生影响。虽然人们预计胚胎发育将受到母体的控制，但更具争议性的假说表明，花粉供体和胚胎本身可能会影响发育。然而，这些后一种可能性研究甚少。本研究以野生萝卜（Raphanus sativus）为例，检测了 10 日龄胚胎和种子的特征，以解决以下问题：（a）母体植物和花粉供体对发育的影响；（b）早期生殖事件（花粉管生长和受精）对胚胎和种子的影响，以及胚胎大小对成熟种子质量的影响；（c）水分胁迫对胚胎和种子的影响；（d）胁迫对胚胎和种子特征与早期和晚期生殖事件和阶段的相关性的影响；（e）在发育过程中，母体和父体对胚胎和种子特征的影响变化。
用来自四个家系的两个母体植物和四个花粉供体进行杂交，在授粉后 10 天收集正在发育的雌蕊。一半的母体植物经历了水分胁迫。总结了胚胎和种子的特征，并与早期和晚期发育阶段进行了比较。
除了母体植物的预期影响外，所有的胚胎特征都因花粉供体而异。父体的影响随时间而变化，这表明花粉供体有机会影响胚胎发育。水分胁迫处理改变了胚胎特征；胚胎更小，发育程度更低。此外，胚胎特征与早期和晚期阶段的相关性随着水分胁迫而发生剧烈变化。
观察到了预期的母体对胚胎发育的影响，但也有早期父体作用的证据。这些控制因素的相对影响可能随时间而变化。因此，在发育过程中，可能存在选择对母体、父体或胚胎对发育的贡献更有可能或更不可能的时间点。
