Pollen development in Picea asperata Mast.

Abstract

In this paper we describe the pollen developmental processes in Picea asperata Mast. by means of cytochemical and ultrastructural methods, with an emphasis on starch grains, callose dynamics and the ultrastructure of prothallial cells. It was observed that microsporogenesis and pollen development of Picea asperata proceeded from early March to late April. The meiosis of pollen mother cells (PMC) was of the simultaneous type and the arrangement of microspores in the tetrad was tetrahedral. A mature pollen grain consisted of four cells. Therefore, the pollen development of this species should be categorized into the Keteleeria type. During meiosis, starch grains and callose had a regular dynamic distribution. At the four-celled stage, the organelles were asymmetrically distributed. The degenerated prothallial cells had some remarkable characteristics that are typical to cells involved in programmed cell death (PCD), a phenomenon observed in some plants and animals. In comparison with other taxa of the Pinaceae, the synchronized development from meiosis of the pollen mother cell to mature pollen together with frequent insect damage to the pollen cones might be a possible cause of frequent low pollen production in this species.