Calcium dynamic in the developing microsporangiums of Chinese fir (Cunninghamia lanceolata)

Abstract Calcium dynamics in the developing pollen of Chinese fir (Cunninghamia lanceolata) were investigated using an antimonate calcium precipitation method. After microspores were released from the tetrad, abundant calcium precipitates formed on the surface of microspores. A characteristic event during microspore development is the formation of a large vacuole which displaces the nucleus to the periphery and produces polarity, which initiates male gametophyte development. During the formation of the large vacuole, calcium precipitates moved into the large vacuole via mitochondria, suggesting that calcium abundance is related to vacuole biogenesis and formation. After microspore division, the large vacuole reorganised and calcium became concentrated in smaller vacuoles. The pollen wall of Chinese fir consists mostly of the intine, composed of polysaccharose, and the surface of the pollen grains is covered with a thin indefinite structure, the exine, which is composed of sporopollenin. The function of calcium during pollen development and the characteristics of the pollen wall of Chinese fir are discussed.