两种姜科花柱卷曲性植物柱头的位置与其可授性的关系

花柱卷曲性是一种见于姜科山姜属(Alpinia)和砂仁属(Amomum)植物中的独特的性二态现象, 具有这一性系统的植物, 其居群包括上举型和下垂型两种表型, 所有个体的雌雄性别功能在时间和空间上分离。本研究通过操控授粉和花粉管生长两项实验, 探讨花柱卷曲性植物个体两性功能的隔离方式及其适应意义。云南草蔻(Alpinia blepharocalyx)操控授粉实验表明, 自花花粉对其异交率影响不显著(P > 0.05), 但可能由于自花花粉沉降导致胚珠贴现进而引起近交衰退, 操控条件下每果结籽数显著减少(P < 0.01)。云南草蔻和红豆蔻(Alpinia galanga)花粉管生长实验都显示无论对两种表型进行怎样的授粉处理, 花粉粒萌发和花粉管生长的速率仅在柱头处于可授位置时表现出最大值, 与自交和异交授粉方式无关; 上举型植株上午花粉囊虽未裂但其内花粉已成熟。研究结果表明即使不考虑花柱运动, 山姜属植物也具有异型雌雄异熟的特性。这一结果证实了花柱卷曲运动机制是通过互补式雌雄异位和异型雌雄异熟相结合形成的花部二态性, 异型雌雄异熟促进了异交, 而花柱运动的功能可能在于避免雌雄干扰。

The relation between stigma position and receptivity in two flexistylous gingers

Flexistyly is a unique sexual dimorphic system found in Amomum and Alpinia species of the gin-ger family (Zingiberaceae). The populations of flexistylous species have two phenotypes, named an anaflex-istylous morph and a cataflexistylous morph, and all individuals of both morphs separate their male and fe-male functions spatio-temporally. We conducted manipulated pollinations and pollen tube growth experi-ments on Alpinia blepharocalyx and A. galanga to detect the manner of separation of male and female func-tions within the individual and its adaptive significance. The results showed that the outcrossing rates of ma-nipulated and natural pollination in the cata-morph did not differ significantly (P>0.05). However, the num-ber of seeds per fruit of manipulated cata-morphs was significantly lower (P<0.01) than that of control indi-viduals, perhaps due to the inbreeding depression caused by ovule discounting. Pollen tube growth experi-ments showed that, when stigma were located at the receptive position (ana-morph in AM, cata-morph in PM), stigma provided appropriate conditions (had stigmatic secretion) for pollen grain germination, and pol-len tubes penetrated into the style within 2 hours after pollination, regardless treatment of selfing or out-crossing. However, when stigma were beyond the anther (ana-morph in PM, cata-morph in AM, without stigmatic secretion), it usually took 6-10 hours for pollen germination and pollen tube penetration. Pollen tubes, however, could reach the ovary within 24 hours under both treatments. Hand-pollination also showed that pollen grains of anaflexistylous flowers have matured before the dehiscence of pollen sacs. Our research suggests that flexistyly is a floral dimorphism comprising reciprocal mobile herkogamy and heterodichog-amy. Heterodichogamy encourages outcrossing, meanwhile reciprocal curvatures of stigmas play a role of reducing interference between male and female functions.