Pak. J. Bot., 40(2): 487-493, 2008. GENERAL MORPHOLOGY AND RELATION BETWEEN POTASSIUM AND POLLEN IN JAPANESE ANGELICA (ARALIA ELATA L.) MUHAMMAD JAMIL 1† , JONG GYUN KANG 2, AND EUI SHIK RHA 3† 1 Department of Biotechnology, Kohat University of Science and Technology (KUST) Kohat 26000, Pakistan 2 Center for University-Wide Research Facilities, Chonbuk National University, Jeonju 561-756, Korea 3 College of Agriculture & Life Sciences, Sunchon National University, Suncheon 540-742, Republic of Korea Abstract Japanese angelica (Aralia elata L.) pollens were collected from the mature central open spikelet having visible anthers and were used for morphological observation. Scanning electron microscope revealed two distinctive types of pollen. One was comparatively larger in size and regular in shape (fertile) while the other was smaller and irregular in shape (sterile). Scanning electron microscope showed that pollen has clearly visible four apertures. It was hypothesized that potassium (K) may be involved in pollen swelling and the mechanisms underlying the rapid imbibition of water. Scanning electron microscopy with EDX (Energy dispersive X-ray) attachment was used to observe K at aperture area of pollen. It was found the K intensity were higher when the beam was passed through the aperture whereas intensity of K peaks reduced when the beam passed through the area that is between apertures. These results support our hypothesis that if K drives rapid imbibition of water then it should be located in the aperture area of pollen. These results demonstrate that a likely relationship exists between K located at the aperture and the swelling of pollen. Introduction Potassium (K) has an essential role in plant water relation as well as in enzyme activation, protein synthesis, photosynthesis and other function (Marschner, 1995). It has been reported that pollen germination and pollen tube growth has significantly regulated by the transport of inorganic ions such as Ca and K (Feijo et al., 1995; Tayler & Hepler, 1997). It is also known that K is required for both pollen germination and tube growth (Brewbaker & kwack, 1963; Feijo et al., 1995). Obermeyer & Blatt (1995) reported that inward K current in a non germinating pollen grain may play a role in initiating the osmotic water influx required for pollen germination. Rehman et al., (2004) reported that mature barley (Hordeum vulgare L.) pollen swell in a fraction of a second upon hydration and the presence of potassium (K) at the aperture area of pollen was considered responsible for the rapid hydration of pollen. Fan et al., (2001) also elaborated the physiological importance of K in Arabidopsis pollen germination and tube growth and K influx may play a role in the regulation of pollen turgor pressure. The presence of potassium (K) at the aperture area of pollen was previously detected by energy dispersive X-ray analysis (EDX) technique in barley (Rehman et al., 2004). †Corresponding author: E-mail: euishik@sunchon.ac.kr, jamil.khattak@kustnet.edu.pk