tailieunhanh - Pollen characters and their evolutionary significance with special reference to the flora of Karachi

The pollen morphology of 353 species from Karachi, belonging to 67 families of angiosperms, distributed in 58 dicots and 9 monocots were investigated by scanning electron microscope (.) and light microscope (.). | Turk J Biol 24 (2000) 365–377 © TÜBİTAK Pollen Characters and Their Evolutionary Significance With Special Reference to the Flora of Karachi Anjum PERVEEN Department of Botany, University of Karachi, Karachi-75270 Received: Abstract: The pollen morphology of 353 species from Karachi, belonging to 67 families of angiosperms, distributed in 58 dicots and 9 monocots were investigated by scanning electron microscope (.) and light microscope (.). Examination of these families revealed great pollen diversity in their qualitative and quantitative characters. However, from a phylogenetic and evolutionary point of view, polarity, symmetry, apertural types and exine sculpturing are the most important characters. In general, dicot pollen is relatively more specialized than that of monocots. Dicotyledons are generally characterized by radially symmetrical, isopolar, colporate, colpate and porate pollen, whereas monocotyledon are usually heteropolar, bilaterally symmetric, boat–shaped, monocolpate and monoporate pollen. With few problematic exceptions, the pollen data supports the general classification. The relatively most primitive pollen type . monosulcate (monocolpate), heteropolar, bilaterally symmetric pollen are restricted to the most primitive subclass of dicots ., Magnoliidae and to the monocots. In contrast to this, the highly advanced subclass Asteridae exhibits the greatest array of specialized pollen types, especially the family compositae. Key Words: Palynology, Evolutionary significance, Flora, Karachi. Özellikle Karachi Florasına Bakarak Polenlerin Özellikleri ve Evrimsel Önemi Özet: Karachi’deki 58 dikot ve 9 monokot şeklinde dağılan, 67 angiosperm ailesine ait olan 353 cinsin polen morfolojisi, tarama elektron mikroskobu (SEM) ve ışık mikroskopu (LM) ile incelenmiştir. Bu ailelerin incelenmesi, nicel ve nitel özelliklerinde büyük ölçüde polen çeşitliliği bulunduğunu göstermiştir. Ancak, filogenetik ve evrimsel bakış açısından, .