Effects of Nuclear Genomes on Anther Development in Cytoplasmic Male Sterile Chicories (Cichorium intybus L.): Morphological Analysis

Table 2

Development of male gametophytes in relation to their size and histology.

Bud length (mm)	Stage	Petal, sepals, and stamens
<0.2	1	Flower primordia emergence
0.2–0.3^*	2	Petal primordia emergence
0.3–0.4^*	3	Stamen primordia emergence, petals bending
0.5	4	Stalked and rounded stamen, trichomes differentiation on petals, pappus primordia initiation
0.6–0.7	5	Oval shaped stamen in cross section, differentiation into anther and filament, differentiation of archesporial tissue
0.8–1	6	Four-lobed anther, filament elongation and vascularization of anther, formation of sporogenous cells and one parietal cell layer
1.2–1.4	7	Appearance of early pollen mother cells (pmc) and second parietal cell layer
1.5–2	8	Four distinguishable anther layers, about 50 pmc longitudinally aligned in each locule, enlargement and vacuolation of tapetum
2–2.5	9	Callose deposition around pmc, meiosis
2.5–3	10	Tetrads of microspores, crushing of middle layer by the enlarging tapetum, nuclear division in tapetum cells
3-4	11	Degradation of callose, release of microspores, disappearance of middle layer, tapetal cell intrusion in the locule
4-5	12	Vacuolate microspore, expansion of endothecium cells, start of septum disintegration
6	13	First pollen mitosis, start of starch accumulation in the pollen grain, secondary thickenings of endothecium cell wall, anthocyanin biosynthesis in the anther
7	14	Two-celled pollen grain, complete degeneration of tapetum
8-9	15	Tricellular pollen grain, completion of septum disintegration, stomium opening, release of pollen grains in the locule
10–12	16	Anthesis, rapid elongation of the floral tube, pollen collection by the style brushing hairs

The bud length was measured under microscope.