Department of Biology, San Diego State University, San Diego, USA.
University of Santa Cruz, San Diego, USA.
BMC Plant Biol. 2022 Mar 2;22(1):94. doi: 10.1186/s12870-022-03431-0.
In certain unisexual flowers, non-functional sexual organs remain vestigial and unisexuality can be overlooked leading to the ambiguous description of the sexual systems. Therefore, to accurately describe the sexual system, detailed morphological and developmental analyses along with experimental crosses must be performed. Cylindropuntia wolfii is a rare cactus endemic to the Sonoran Desert in southern California and northern Baja California that was described as gynodioecious by morphological analysis. The aims of our project include accurately identifying the sexual system of C. wolfii using histological and functional studies and characterizing the developmental mechanisms that underlie its floral development.
Histological analyses were carried out on different stages of C. wolfii flowers and controlled crosses were performed in the field.
Our results identified C. wolfii to be functionally dioecious. The ovule and anther development differed between staminate and pistillate flowers. In vivo pollen germination tests showed that the pollen of staminate and pistillate flowers were viable and the stigma and style of both staminate and pistillate flowers were receptive. This suggests that there are no genetic or developmental barriers in the earlier stages of pollen recognition and pollen germination.
Despite being functionally dioecious, we observed that functionally pistillate individuals produced fruits with a large number of aborted seeds. This implies that not only does this species have low reproductive success, but its small population sizes may lead to low genetic diversity.
在某些单性花中，非功能性性器官仍然是退化的，单性可能被忽视，导致对性系统的描述模棱两可。因此，为了准确描述性系统，必须进行详细的形态学和发育分析以及实验性杂交。Cylindropuntia wolfii 是一种罕见的仙人掌，分布于南加州和北下加利福尼亚的索诺兰沙漠，其形态学分析被描述为雌雄异株。我们项目的目的包括使用组织学和功能研究准确识别 C. wolfii 的性系统，并描述其花发育的发育机制。
对 C. wolfii 花的不同阶段进行组织学分析，并在野外进行控制性杂交。
我们的结果表明 C. wolfii 实际上是功能上的雌雄异株。雄花和雌花的胚珠和花药发育不同。体内花粉萌发试验表明，雄花和雌花的花粉均具有活力，且两性花的柱头和花柱均具有接受性。这表明在花粉识别和花粉萌发的早期阶段不存在遗传或发育障碍。
尽管是功能上的雌雄异株，但我们观察到功能上的雌性个体产生的果实中有大量的败育种子。这意味着该物种不仅繁殖成功率低，而且其小种群数量可能导致遗传多样性低。
