Huang Zehao, Zhu Jinmao, Mu Xijin, Lin Jinxing
Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 100093 Beijing, China.
Ann Bot. 2004 Mar;93(3):295-301. doi: 10.1093/aob/mch044. Epub 2004 Jan 26.
Leymus chinensis is an economically and ecologically important grass that is widely distributed across eastern areas of the Eurasian steppe. A major problem facing its propagation by man is its low sexual reproductivity. The causes of low fecundity are uncertain, largely because many aspects of the reproductive biology of this species remained unknown or incomplete. This study aims to address some of these issues.
Pollen dispersion, pollen viability, pollen longevity and pistil receptivity were studied in a representative, natural population of L. chinensis growing in Inner Mongolia.
Flowering of L. chinensis occurred at the end of June and lasted for 5 d. Pollination peaked between 1600 h and 1700 h, and about 56.1 % of the total pollen grains were released at this time. Pollen density was highest towards the middle of flowering spikes and lowest at the bottom over the 5 d measurement period. Pollen viability (62.4 %) assessed using TTC was more accurate than using IKI (85.6 %); 50 % of pollen arriving on stigmas germinated. Pollen remained viable for only 3 h and the pollen : ovule ratio was 79 333 : 1. Pistil receptivity lasted for only 3 h and, overall, 86.7 % of pistils were pollinated. Within the spike, the relative fecundity of different positions was middle > lower > upper throughout the period of pollination; daily variation of fecundity was similar to that of the pollen flow. The spikes that opened on the day of highest pollen density exhibited the highest fecundity (36.0 %). No seeds were produced by self-pollination.
The data suggest that low pollen viability, short pollen longevity and short pistil receptivity all appear to contribute to the low seed production typical of this important forage crop.
羊草是一种具有重要经济和生态价值的禾本科植物，广泛分布于欧亚大陆草原东部地区。人工繁殖羊草面临的一个主要问题是其有性繁殖能力较低。繁殖力低下的原因尚不确定，主要是因为该物种生殖生物学的许多方面仍不为人知或不完整。本研究旨在解决其中的一些问题。
在内蒙古一个具有代表性的天然羊草种群中，对花粉传播、花粉活力、花粉寿命和雌蕊可授性进行了研究。
羊草于6月底开花，花期持续5天。授粉高峰出现在16:00至17:00之间，此时约56.1%的花粉粒释放。在5天的测量期内，花粉密度在开花穗中部最高，底部最低。用TTC法测定的花粉活力（62.4%）比用IKI法（85.6%）更准确；到达柱头的花粉有50%萌发。花粉仅能存活3小时，花粉与胚珠比为79333:1。雌蕊可授性仅持续3小时，总体上86.7%的雌蕊授粉。在穗内，不同位置的相对繁殖力在整个授粉期内均为中部>下部>上部；繁殖力的日变化与花粉流相似。在花粉密度最高的当天开放的穗表现出最高的繁殖力（36.0%）。自花授粉未产生种子。
数据表明，花粉活力低、花粉寿命短和雌蕊可授性短似乎都导致了这种重要饲料作物典型的低种子产量。
