10份柠檬种质花粉形态观察

为了明确柠檬不同种质花粉的形态特征及各种质之间的亲缘关系,为柠檬种质的鉴定和创新利用提供重要的参考,本研究以10份柠檬种质的花粉为试材,通过场发射环境扫描电镜对花粉形状,花粉大小及花粉外壁纹饰等形态特征进行观察,并进行比较分析。研究结果表明：柠檬花粉存在形式为单粒,花粉粒外部形态呈圆球形、近长球形或长球形,具有4~5条萌发孔沟,萌发孔沟沿极轴方向以等距环状分布,沟长直达两极。不同种质的花粉形状、花粉大小、花粉外壁网眼密度和网眼大小等均存在差异。极轴长33.56~41.20 μm,赤道轴长22.06~33.70 μm,花粉大小（P×E）为844.90~1385.98 μm²。花粉外壁纹饰为网状雕纹,网脊宽为0.39~0.88 μm,网眼直径为0.87~1.68 μm,网眼表现为圆形、近圆形或不规则多角形。花粉大小等级为中等,极面观为四裂圆形或五裂圆形,赤道面观为圆形,椭圆形或长椭圆形。10份柠檬种质在花粉形状、大小、外壁纹饰等方面表现出多样性,可作为区分柠檬不同种质的依据。

Observation on Pollen Morphology of 10 Lemon Germplasms

Pollen morphology has a certain value in conservatism, so it is often used as a classification basis for plant resources. In order to clarify the pollen morphology and relationship among different lemon germplasms, which would provide an important reference for the identification and innovative utilization of different lemon germplasms. In the flowering period (February to March), the flowers were picked up in the upper part of the crown periphery from robust plants, and the petals and calyx were removed with sterile tweezers. The anthers were placed indoors in the shade for 3 days. The pollens were collected and stored at low temperature. The pollens were used as the test materials and the morphological characteristics of pollen shape, pollen size and pollen exine ornamentation morphology were observed by the field emission environmental scanning electron microscope. Six quantitative features, including equatorial axis length, polar axis length, polar axis equatorial axis ratio, polar axis equatorial axis product, width of net ridge, mesh number were investigated. Data were normalized by DPSv3.01 software and clustered. The genetic distance was calculated as the euclidean distance, and the UPGMA method was used for the cluster analysis. The results showed that lemon pollen existed in the form of single grain, which was spherical, long spherical, nearly spherical, with 4-5 germination pore grooves. The germination pore grooves were distributed in an equidistant ring along the polar axis, and the groove length reached the two poles. The pollen shape, pollen size, mesh density and mesh diameter were different. The polar axis length was 33.56-41.20 μm. The equatorial axis length was 22.06-33.70 μm. The pollen grain (P×E) size was 844.90-1385.98 μm². The pollen exine ornamentation was reticular ornamentation. The width of net ridge was 0.39- 0.88 μm. The mesh diameter size was 0.87-1.68 μm. The mesh was round, nearly round or irregular polygon. The pollen was medium-sized, the polar view was tetragonal or pentagonal, and the equatorial view was round, elliptic or oblong. Ten lemon germplasms showed diversity in pollen shape, size and exine ornamentation morphology, which could be used as a basis to distinguish different lemon germplasms. Femminello lemon (4×) had the largest pollen grain size, which was significantly larger than that of other germplasms. However, since only Femminello lemon (4×) was a ploidy variant in this study, whether the ploidy of lemon could be identified by observing the size of pollen needs further research.