Morfometria, desenvolvimento pós-seminal e morfoanatomia de estruturas reprodutivas de cambuí [Myrciaria floribunda (H. West ex Willd.) O. Berg.]

Abstract

Rumberry (Myrciaria floribunda) is a native tropical fruit tree of the Myrtaceae family that has interesting potential value for the agribusiness. This species occurs naturally in coastal areas of several Brazilian states and, mainly, in restingas on the southern coast of the state of Alagoas. Due to the possibility that the species will soon have a vast demand, it is necessary to establish a wide seedling propagation system, which has normally been done seminally due to the lack of selected varieties and vegetative propagation methods. Cambui seeds present a slow germination process, which leads to the need for studies that identify the factors that hinder the event. This work aimed to characterize cambuí seeds and to evaluate their germinative process in vitro and ex vitro, characterizing through structures scanning electronic microscopy (SEM) some structures associated with their sexually propagated apparatus. The biometry of 400 seeds was performed, evaluating the relative frequency of their diameters. For the ex vitro test, germination was done in Petri dishes with seeds at different times of imbibition / absorption in water with the presence or absence of the integument. A 3 x 4 factorial scheme was used, with three treatments for the integument (1- with integument; 2- cracked integument and 3- without integument) and different imbibition times (0h, 24h, 48h, 72h). For the in vitro test, the seeds were submitted to the germination test using a completely randomized design with a 2 x 3 scheme, using seeds with and without tegument in different culture media (water + agar; water + agar + half of the MS salts ; and water + agar + complete MS). After 90 days, the percentage of germination, the speed índex and the average germination time, root and shoot development were evaluated in the ex vitro test. For the in vitro test, at 150 days the root and shoot development was evaluated. According to the results obtained, cambuí seeds have an elliptical or oval shape (DL / DT> 1). In the total absence of the tegument, the seeds showed a higher percentage of germination ex vitro regardless of the imbibition treatment. In vitro germination was also influenced by the absence of the tegument in the seeds, showing a better development of the root and shoot in a culture medium containing water + agar. The material collected for SEM consisted of flower buds, fruits and seeds at different stages of development. The scanning electron micrographs described the flower buds as obconic and / or globose, androceu presenting an oligostêmone characteristic. Dialistemone filiform fillet, with uni-stratified epidermis and conate anthers that come off with the opening of the flower. The stamens were distributed with variable numbers, containing pollen grains. The immature fruit showed conspicuous glands. The germination of the cambuí seed started with an expansion of the root protrusion region, then breaking the integument. The embryo in the mature seed had a single, long and thick hypocotyl-radicle axis, with vestigial cotyledons. The welding line was found in most of the analyzed seeds, regardless of the genotype in question. Cambuí seeds have an integumentary barrier, composed of structures that may be responsible for the late germination in natural conditions.