Histochemical analysis of seed reserve mobilization in Passiflora edulis Sims fo. flavicarpa O. Deg. (yellow passion fruit) during germination / Análise histoquímica da mobilização de reservas em sementes de Passiflora edulis Sims fo. flavicarpa O. Deg (maracujá amarelo) durante a germinação

In the present work, we analyzed the histochemical aspects of Passiflora edulis seeds reserve mobilization during the first ten days of germination. Our results showed that mainly lipids present in the endosperm are used as a reserve source, and their levels reduce at the same time the radicle protrudes, between the fourth and sixth day of sowing. Furthermore, protein bodies are present in the cotyledons, which are degraded as germination occurs and are almost depleted by the time of radicle protrusion. Starch grains also appear in the late germination period, and it is not clear if there is any reserve wall polysaccharide consumption in the endosperm.

No presente trabalho analisamos os aspectos histoquímicos da mobilização de reservas das sementes de Passiflora edulis, durante os primeiros dez dias de germinação. Nossos resultados mostraram que principalmente lipídios presentes no endosperma são utilizados como reserva, com o seu nível começando a diminuir ao mesmo tempo em que ocorre a protrusão da radícula, entre o quarto e sexto dia do início da embebição. Corpos proteicos também estão presentes nos cotilédones, e são degradados à medida que ocorre a germinação e são consumidos quase totalmente quando da protrusão da radícula. Grãos de amido também aparecem no período tardio de germinação, e não está claro se há ou não consumo de polissacarídeos de reserva de parede no endosperma.

Embryo sac development in yellow passion fruit Passiflora edulis f. flavicarpa (Passifloraceae)

The yellow passion fruit, Passiflora edulis f. flavicarpa, is one of the most important Brazilian fruit crops. It is an allogamous, diploid, and self-incompatible species. It has hermaphrodite, solitary flowers, located in the leaf axils and protected by leaf bracts. The flower has an androgynophore, which is a straight stalk supporting its reproductive parts. There are usually five anthers, located at the tip of each of the five filaments. The ovary is borne just above the filaments, at the top of the androgynophore; there are three styles that are united at their base, and at the top there are three stigmas. The objective of this research was to observe embryo sac development in yellow passion flowers. Ovaries at different stages of development were fixed in FAA (formalin, acetic acid and alcohol solution), hydrated, stained with Mayer's hemalum, and dehydrated. Ovules were cleared by using methyl salicylate, mounted on slides, and observed through a confocal scanning laser microscope. The yellow passion fruit ovule is bitegmic, crassinucellate, and anatropous, and its gametophyte development is of the Polygonum type. After meiosis, functional megaspores under go three successive mitotic divisions, resulting in an eight-nucleate megagametophyte: the egg apparatus at the micropylar end, two polar nuclei at the cell center, and three antipodals at the chalazal end. The egg apparatus is formed by an egg cell and two synergids, each with a filiform apparatus. The mature embryo sac has an egg cell, two synergids, two polar nuclei, and three antipodes, as has been described for most angiosperms