Studies on meiosis in pollen mother cells (PMCs) of a triploid interspecific hybrid (3x = 39 chromosomes, AAD) between tetraploid Gossypium hirsutum (4n = 2x = 52,AADD) and diploid G. arboreum (2n = 2x = 26,AA) are reported. During meiotic metaphase I, 13 AA bivalents and 13 D univalents are expected in the hybrid. However, only 28% of the PMCs had this expected configuration. The rest of the PMCs had between 8 and 12 bivalents and between 12 and 17 univalents. Univalents lagged at anaphase I, and at metaphase II one or a group of univalents remained scattered in the cytoplasm and failed to assemble at a single metaphase plate. Primary bipolar spindles organized around the bivalents and multivalents. In addition to the primary spindle, several secondary and smaller bipolar spindles organized themselves around individual univalents and groups of univalents. Almost all (97%) of the PMCs showed secondary spindles. Each spindle functioned independently and despite their multiple numbers in a cell, meiosis I proceeded normally, with polyad formation. These observations strongly support the view that in plant meiocytes bilateral kinetochore symmetry is not required for establishing a bipolar spindle and that single unpaired chromosomes can initiate and stabilize the formation of a functional bipolar spindle.

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Choosing suitable varieties and manipulating plant population are crucial management aspects in any cropping system that goals to improve yield, quality and the balance between plant demand and environmental resource availability. A two-year field experiment was conducted at Tehran, Iran, in a split plot design and replicated thrice to examine the effect of the planting density (low, moderate and high) on ten cotton genotypes. In term of lint yield and among the cotton genotypes G8 (1269 kg · ha−1), G4 (1263 kg · ha−1), G1 (1239 kg · ha−1) and G2 (1123 kg · ha−1) were statistically at par with each other but significantly superior to G7 (914 kg · ha−1) and G9 (936 kg · ha−1). Lint yield in high plant density (1386 kg · ha−1) was found to be remarkably superior over medium and low plant density (1029 and 890 kg · ha−1, respectively) by average of 25.7% and 35.7%, respectively. Cotton genotypes at low plant density had higher boll plant−1 (6.46% and 15.3%, respectively), lint percentage (5.8% and 12%, respectively) and lint strength (0.6% and 1.9%, respectively) compared to moderate and high plant densities. The genotypes cultivated at high plant density produced higher seed and lint yield, higher lint elasticity and lower seed oil content, lint length and lint quality index. Based on this experiment, it is concluded that high seed cotton yield can be achieved at high plant density while higher lint quality can be yielded at low plant density.