Unreduced diploid nuclei in Cupressus dupreziana A. Camus pollen

Size and DNA content of pollen of Cupressus dupreziana A. Camus, a highly e ndangered Mediterranean conifer, were assessed by cytomorphological observa tions and flow cytometric analyses and then compared to C. sempervirens L. pollen. Mature C. dupreziana pollen was composed of two uninucleated types of pollen grains differing in size. Around 35% of the grains exhibited a si ze similar to C. sempervirens pollen, while 65% exhibited a larger diameter . However only one peak of fluorescence was detected by flow cytometry. DNA content of C. dupreziana pollen was twice the DNA content of C. sempervire ns pollen. Comparison of DNA contents of mature and germinating pollen reve aled that mature pollen of both species were arrested in the G2 phase. Comp arison with the DNA content of somatic tissue (2C) provided evidence for th e production of unreduced pollen in C. dupreziana. This unexpected feature in gymnosperms is discussed in terms of reproductive strategy of this speci es.