Dipartimento di Scienze delle Produzioni Agrarie e Alimentari, University of Catania, Catania 95123, Italy.
Ann Bot. 2011 Sep;108(3):499-509. doi: 10.1093/aob/mcr187. Epub 2011 Jul 27.
An intense pollen-pistil interaction precedes fertilization. This interaction is of particular relevance in agronomically important species where seeds or fruits are the edible part. Over time some agronomically species have been selected for the ability to produce fruit without seeds. While this phenomenon is critical for commercial production in some species, very little is known about the events behind the production of seedless fruit. In this work, the relationship between pollen-pistil interaction and the onset of fruiting was investigated in citrus mandarin.
Pistils were sequentially examined in hand-pollinated flowers paying attention to pollen-tube behaviour, and to cytochemical changes along the pollen-tube pathway. To evaluate which of these changes were induced by pollination/fertilization and which were developmentally regulated, pollinated and unpollinated pistils were compared. Also the onset of fruiting was timed and changes in the ovary examined.
Conspicuous changes occurred in the pistil along the pollen-tube pathway, which took place in a basipetal way encompassing the timing of pollen-tube growth. However, these changes appear to be developmentally regulated as they happened in the same way and at the same time in unpollinated flowers. Moreover, the onset of fruiting occurred prior to fertilization and the very same changes could be observed in unpollinated flowers.
Pollen-pistil interaction in citrus showed similarities with unrelated species and families belonging to other taxa. The uncoupling of the reproductive and fruiting processes accounts for the parthenocarpic ability of unpollinated flowers to produce fruit in citrus. However, the maintenance of a functional reproductive process reflects the potential to produce seeded fruits, providing a basis for the understanding of the production of seeded or unseeded fruits and further understanding of the process of parthenocarpy in other species.
授粉前花粉-雌蕊之间会发生强烈的相互作用。这种相互作用在农业上很重要，因为种子或果实是可食用的部分。随着时间的推移，一些农业上重要的物种被选择具有不产生种子就能产生果实的能力。虽然这种现象在某些物种的商业生产中至关重要，但对于无籽果实产生背后的事件却知之甚少。在这项工作中，研究了柑橘甜橙中花粉-雌蕊相互作用与果实开始形成之间的关系。
在手授粉花朵中，依次检查雌蕊，注意花粉管行为以及花粉管途径中的细胞化学变化。为了评估哪些变化是授粉/受精诱导的，哪些是发育调控的，比较了授粉和未授粉的雌蕊。还对果实开始形成的时间和子房的变化进行了评估。
在花粉管途径中，雌蕊发生了明显的变化，这些变化呈向基性发生，涵盖了花粉管生长的时间。然而，这些变化似乎是发育调控的，因为它们在未授粉的花朵中以相同的方式和时间发生。此外，果实开始形成发生在受精之前，在未授粉的花朵中也可以观察到相同的变化。
柑橘中的花粉-雌蕊相互作用与其他类群的无关物种和科具有相似性。生殖和果实形成过程的解耦解释了未授粉花朵具有产生果实的单性结实能力的原因。然而，维持一个功能性的生殖过程反映了产生有籽果实的潜力，为理解有籽或无籽果实的产生以及进一步理解其他物种的单性结实过程提供了基础。
