Figure 3. Comparison of the anther, tapetum and pollen development under drought stress and recovery conditions. (A)Cross-sections of anthers at six different stages of development under DS and recovery conditions. WW , anthers from well-watered plants; DS (4 d), anthers from drought-stressed plants after 4 d of DS; type-2 and type-3 , anthers (DS at meiotic stage)from drought-stressed and rewatered plants between 1-11 and 1-12 days after rewatering respectively depending on the stage of development. MEI, meiotic; TED, tetrad; EUM, early uninucleate microspore; VUM, vacuolated uninucleate microspore; BIN, binucleate; MP, mature pollen; E, epidermis; En, endothecium; ML, middle layer; OT, outer tapetum; SM, septum; StR, stomium region; IT, inner tapetum; MC, meiotic cell; C, connective tissue; Td, tetrad; T, tapetum; MS, microspore; PG, pollen grain; St, stomium. (B) Transmission electron micrographs (TEMs) of developing pollen. Cw, cell wall; Nu, nucleolus; N, nucleus; Md, middle lamella; Ca, callose; W, pollen wall; V, vacuole: Fu, furrow; VN, vegetative nucleus; GN, generative nucleus; AP, aperture; S, starch granule. (C) TEMs of developing tapetum. ML, middle layer; Ubi, ubisch body; Pd, plasmodesma. Arrows: 1, gap between disengaged sporogenous and tapetum tissues; 2, aborted pollen; 3, precocious anther dehiscence; 4, abnormally enlarged pollen; 5, persistent stomium cells adhered to connective tissue; 6, collapsed anther; 7, persistent stomium cells adhered together; 8, empty locules; 9, debris of degenerated microspore; 10, gap between pollen wall and pollen protoplasm; 11, gap between tapetum wall and shrank tapetum cell protoplasm; 12, gap between two adjacent tapetum cells; 13, gap between tapetum and middle layer cells. Spots with the same number depict the same feature.