外源钙对花粉管胞吞/胞吐速率和细胞壁成分的影响

Effects of excellular calcium on exocytosis / endocytosis rate and cell wall components of pollen tube

为了探索花粉管生长调控的机制,本研究利用花粉管模型,结合超微结构观察测量花粉管的内径,壁厚,囊泡大小,首次定量分析了花粉管生长速度变化过程中的胞吞和胞吐速率变化。结果发现在0.01%外钙浓度下花粉管平均生长速率为(8.74±1.83)μm/min,胞吐速率9 043个/min,胞吞速率344 749个/min;在0.3%浓度下花粉管均生长速率为(3.47±0.93)μm/min,胞吐速率12 873个/min,胞吞速率517 738个/min;这证明了花粉管生长速度与胞吞胞吐速率不成直接的正比关系。其次通过细胞壁成分的荧光标记观察,还发现在0.3%的外钙浓度下,花粉管细胞壁中胼胝质明显增加,顶端生长点细胞壁内纤维素和酸性果胶略有增多。这表明细胞壁成分的变化对于花粉管生长速度的调节有着重要的影响。

In order to decipher the mechanism underlying pollen tube growth, exocytosis/endocytosis rates of Lili pollen tubes cultured in medium with excellular calcium at different concentrations were first quantitatively compared base on an algorithm using growth velocities of pollen tubes, widths of pollen tube lumens, thicknesses of cell walls, and diameters of endocytosis and exocytosis vesicles. The results showed that pollen tubes cultured in medium with 0.01% calcium grew at mean velocity of （8.74 ± 1.83）μm/min, which required exocytosis rate of 9 043 events/min and endocytosis rate of 344 749 events /min; while as in 0.3% calcium, pollen tubes grew at mean velocity of （3.47 ± 0.93）μm/min, which required exocytosis rate of 12 873 events/min and endocytosis rate of 517 738 events /min, suggesting there is no certain positive correlation between growth velocity of pollen tube and exocytosis/endocytosis rate. Moreover, fluorescence labeling of cell wall components revealed that, compared with 0.01% calcium in medium, 0.03% calcium obviously induced callose in cell walls along whole pollen tubes, and caused a bit of increase of cellulose and acidic pectin at apical cell walls, indicating that cell wall components played important roles in the regulation of growth velocity of pollen tube.