Induced syncyte formation via cytomixis in Trachyspermum ammi (L.) Sprague (Apiaceae)

Figures & data

Table 1. Effect of gamma rays on the frequency of cytomixis and syncyte formation during microsporogenesis of Trachyspermum ammi (L.) Sprague.

		Cytomixis (%)				Frequency of cells showing cytomixis at various stages of meiosis (%)
			Types of cytomixis			Meiosis I						Meiosis II
						PI
Treatment Doses (Gy)	Total number of PMCs observed	Frequency of PMCs involved	CC	DF	Frequency of syncytes (%)	Pt	Dp	Dk	MI	AI	TI	MII	AII	TII	Other chromosomal abnormalities (%)
Control	348	-	-	-	-	-	-	-	-	-	-	-	-	-	-
100	332	7.6 ± 0.26	68.0	32.0	2.3 ± 0.33^a	2.3	1.4	1.2	1.7	0.3	0.3	-	-	0.7	9.9 ± 0.22^a
200	348	9.5 ± 0.21	66.7	33.3	4.7 ± 0.33^b	2.3	1.2	1.4	2.0	0.4	0.4	0.3	0.4	1.1	12.7 ± 0.17^b
300	325	13.3 ± 0.25	74.4	25.6	5.3 ± 0.33^b	2.9	1.5	1.9	2.7	0.6	0.9	0.7	0.6	1.3	16.4 ± 0.16^c

Abbreviations: CC, cytomictic channel; DF, direct fusion; PI, prophase I; Pt, pachytene; Dp, diplotene; Dk, diakinesis; MI, metaphase I; AI, anaphase I; TI, telophase I; MII, metaphase II; AII, anaphase II; TII, telophase II. Values followed by the different superscripts within same column differ at P < 0.05 between treatments by the DMRT.

Figure 1. (a) A PMC showing nine bivalents at diakinesis; (b) PMCs showing chromatin migration at early prophase-I (arrowed); (c) chromatin transfer through single and multiple cytoplasmic channels; (d) PMCs showing chromatin transfer through single cytoplasmic channel; (e) migration of a single chromosome (arrowed) through narrow cytoplasmic channels; (f) transfer of bivalents through broad cytoplasmic channel; (g) a group of PMCs showing chromatin migration between adjacent meiocytes; (h) unification of two meiocytes by direct fusion of walls; (i) PMCs showing resulting hypoploid (n = 1 + 3 + 2 small sticky fragments, n = 6 + 2 small fragments) and hyperploid (n = 9 sticky+ 2 small fragments, 9 + 2 small fragments) PMCs; (j) bidirectional transfer of bivalents from one meiocyte to two proximate meiocytes (two hypoploid PMCs and one hyperploid PMC); (k) two PMCs, one is donor and the adjacent is recipient; (l) channel formation at telophase II. Scale: 10 µm.

Table 2. Effect of gamma rays on the post-meiotic products, fertility and size of pollen grains of Trachyspermum ammi (L.) Sprague.

		Sizes of heterosized pollen grains (µm)
Treatment doses (Gy)	Pollen fertility (%)	Large	Medium	Abnormal sporads (%)	Relative frequency of heterosized pollen grains (%)
Control	97.9 ± 0.22^d	18.3 × 8.3		-	100
100	79.5 ± 0.12^c	19.2 × 11.8	16.9 × 6.7	11.5 ± 0.15^a	3.6 ± 0.10^l 96.4 ± 0.10^m
200	67.8 ± 0.10^b	21.8 × 15.8	18.3 × 6.7	20.7 ± 0.13^b	5.5 ± 0.15^l 96.5 ± 0.15^m
300	58.6 ± 0.13^a	23.5 × 16.8	18.3 × 8.8	26.4 ± 0.15^c	6.8 ± 0.08^l 93.2 ± 0.15^m

Abbreviations: l, large; m, medium. Values followed by the different superscripts within same column differ at P < 0.05 between treatments by the DMRT.

Figure 2. (a) Syncyte (tetraploid) with 18 bivalents at diakinesis; (b) hyperploid PMC with 27 bivalents; (c) enucleated PMC; (d) pentad; (e) two sporads in which one is normal, i.e. tetrad and other is hexad; (f) triad; (g) dyad; (h) fertile heterosized pollen grains; (i) fertile jumbo sized pollen grain. Scale: 10 µm.