Within the tree height, there was a trend for pollen density to increase with height.

在树高范围内，花粉浓度有由下至上增加的趋势；

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Making use of the culture techniques to regulate the heading date and the pollen density are very important to increase the seed yield of the seed production in the hybrid rice.

利用栽培技术来调节花期和花粉密度，对提高制种产量有重要作用。

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The pollen viability by using different culture method had differences and there were a certain correlation between the pollen density and pollen viability.

用不同的培养方式时棕榈花粉生活力存在差异，花粉培养密度与花粉生活力存在一定相关性；

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