Starch distribution in anthers, microspores and pollen grains in Aechmea recurvata (Klotzsch.) L.B.Sm., Dyckia racinae L.B.Sm. and Tillandsia aeranthos (Loisel.) L.B.Sm. (Bromeliaceae)

Abstract

This paper presents a comparative description of the starch distribution in the anthers, microspores and pollen grains of Aechmea recurvata, Dyckia racinae and Tillandsia aeranthos. Flowers at different stages of development were processed according to plant microtechniques for observation by light microscope. Ten stages of embryological development were used as references for the comparative analysis of starch distribution and dynamics. The structural data showed a greater starch accumulation in the parietal layers and connective of D. racinae. It was observed that in the species studied, starch began to accumulate in microspore mother cell stage. The pollen grains in D. racinae and in T. aeranthos present two amylo genesis-amylolysis cycles, while A. recurvata presents only one. One amylogenesis-amylolysis cycle occurs in the parietal layers and/or connective tissue in all three species. The pollen grains in the three species are dispersed without starch and are characterized as the starchless type. Starch dynamics presents a close relation to the development of sporangia, microspores and pollen grains. It is believed that differences in the starch distribution and accumulation are related to the abiotic factors where the species are found. IntroductionThe effectiveness of the reproductive process in angiosperms depends on the viability of microspores, megaspores, pollen grains and embryo sac, where the dynamics and use of primary metabolites are essential in this process (Bhandari 1984;Delph et al. 1997;Shivanna 2003;Pacini et al. 2006;Konyar et al. 2013). The accumulation and mobilization of sugars, lipids and proteins are common during sporangia development and were demonstrated by microscopy, histochemistry, and biochemical, physiological and molecular assays (Pacini & Viegi 1995;Oliver et al. 2005;Lora et al. 2012;Konyar et al. 2013). Regarding to the sugars, their importance was demonstrated for maturation of the epidermis, endothecium and tapetum (Clément & Audran 1995;Clément et al. 1998;Castro & Clément 2007). In this subject, was also demonstrated that the middle layers also act in the access of sugars to the loculus (Clément & Audran 1995).Besides to supply the metabolic demand, sugars will compose the fibrous thickenings of the endothecium, the primexine and intine, and in some cases, also the exine (Walter & Doyle 1975;Horner & Pearson 1978). When preparing for the developmental events of pollen grains, including the pollination period, sugars can be accumulated as starch, callose, pectins, insoluble polysaccharides, disaccharides or monosaccharides (Pacini 1996;Aouali et al. 2001;Clément & Pacini 2001;Pacini et al. 2006). The starch acts on the metabolism or has a structural function (Pacini 1996). In metabolism, starch can be emphasized as an intermediate stage in the formation of oils in starchlesstype pollen grains (Miki-Hirosige & Nakamura 1983;Baker & Baker 1979). It may be possible for it to convert into sucrose for breathing and osmotic regulation (MikiHirosige & Nakamura 1983), o...

Pseudopollen in Camellia oleifera and its implications for pollination ecology and taxonomy

“…Additionally, with the development and maturity of pseudopollen, intracellular polysaccharide content gradually decreased. Intracellular polysaccharides can be stained pink/purple by PAS, and fluorescence microscopy can clearly distinguish between non-polysaccharides with strong fluorescence reactions and insoluble polysaccharides without fluorescence ( de Oliveira et al, 2015 ; Song et al, 2015 ; Chawla et al, 2017 ). In our study, the early maturing cells were rich in polysaccharides.…”