两种鹤虱属短命植物的繁育系统及其对荒漠环境的适应

两形果鹤虱（^{Lappula duplicicarpa}）和异形狭果鹤虱（^{L. semiglabra}）是两种广泛分布于新疆准噶尔荒漠的具异形果实的早春短命植物。两种植物同一花中均能产生两种形态、脱落及扩散方式明显不同的小坚果，且同一花序上不同部位的花中产生的异形果实比例不同。重点对两种植物的繁育系统与异形果实的产生是否存在联系，以及它们与准噶尔荒漠环境相适应的特点进行了观察。结果表明：①二者花均为两性，植株上同一花中以及花序上产生不同比例异形果实的花之间在花各部的数目与形态、单花花粉量(P)、胚珠数(O)和P/O值上表现均很稳定，与异形果实的产生没有直接联系。②单花花期一般在24 h左右，开花时间不受气候因素的影响。③两种植物的花粉育性均很高，花粉可育率分别为(91.0±4.7)％和(93.2±4.3)％。④散粉时二者的花粉活力均不高，散粉后花粉活力的动态变化基本一致，最佳授粉期分别在2 h和3 h以内，柱头的最佳可授期均在3 h以内，花粉的最佳授粉期与柱头的最佳可授期高度吻合。⑤ 两种植物的P/O值分别为1 222±197和3 419±426，属于混合式繁育系统，这与套袋实验及自花授粉的荧光显微观察结果相一致。⑥ 两种植物在繁育系统上所表现出的特点，避免了准噶尔荒漠的多风、温湿度变化大等恶劣环境条件对其开花、传粉过程的不利影响，保障了繁殖成功。这些结果将为探讨短命植物对准噶尔荒漠的生态适应机制提供重要的理论依据。

Breeding System of Two Ephemeral Species of Lappula and their Adaptations to Desert Environment

Lappula duplicicarpa and L. semiglabra（Boraginaceae）are early-spring ephemerals common in the Junggar Desert. They produce heteromorphic fruits, and nutlets developed from each flower differ in their morphology, pattern of detachment and method and distance of dispersal. The proportion of heteromorphic fruits may differ between infructescences. The following questions were asked about these two species: ①Is there a direct relationship between breeding system and production of heteromorphic fruits? ②How are the breeding system characteristics adapted to the Junggar Desert environment? The results are as follows: ①Flowers of both species are bisexual. The flower morphology, pollen number, ovule number or P/O ratio of individual flowers or of the “population” of flowers in the inflorescence had no direct relationship to the production of heteromorphic nutlets. ②The anthesis of individual flowers in both species lasted about 24 h and was not affected by weather conditions. ③The fertility rates of pollen were (91.0±4.7)％ (mean±SE) in L. duplicicarpa and (93.2±4.3)％ in L. semiglabra. ④In both species, the pollen viability was low at the beginning of anther dehiscence (71% in L. duplicicarpa and 65% in L. semiglabra), and the survivorship (viability) curves for pollen were similar. The optimal pollination period was 0~2 h and 0~3 h after anthesis in L. duplicicarpa and L. semiglabra, respectively, and the optimal stigma receptivity for both species was 0~3 h after anthesis. Thus, the optimal pollination period was highly correlated with the period of high stigma receptivity. ⑤The P/O ratios of L. duplicicarpa and L. semiglabra were 1 222±197 and 3 419±426, respectively. The breeding system of both species is facultative mixed, which is consistent with the results of bagging experiments and with observation on pollen tube growth in stigmas of selfed flowers using fluorescence microscopy. Thus, we conclude that the breeding system of L. duplicicarpa and L. semiglabra ensure reproductive success of both species in the unpredictable environment of the Junggar Desert.