Red fruit (Pandanus conoideus Lam.) is widely spread in Maluku, Papua and Papua New Guinea. Traditionally, the tribes in the interior of Maluku and Papua utilize the red fruit oil for sautéing vegetables and the sauce/paste for seasoning sweet potatoes and sago (Sadsoeitoeboen, 1999) as well as for dying (Sutarno, 2001). The fruit, in addition, can be used to treat number of diseases such as cancer, diabetes mellitus, rheumatoid, uric acid, asthma, high blood pressure, lung, heart disorders and kidney (Wiryanta, 2005).
For the local people in Papua, the propagation of red fruit seed was done by using vegetative buds (Sadsoeitoeboen, 1999; Makaruku 2008; Limbongan, 2009), since the seeds have low vigor and germination rate. Sadjad (1980) stated that the dormancy occured in the red fruit seed because of undifferentiated embryo. Additionally, the seed does not well germinate as a tissue that surrounds the embryo provides barriers (seed coat including the endosperm, pericrap or extrafloral organ) so that the embryo does can not grow (Bewley and Black 1994). Anonymous (2008) noted that the red fruit seed dormancy is caused by a hard seed coat. This condition prevents the absorption of water into the embryo and slows downthe seed growth. The embryos also have difficulty to penetrate the seed coat during germination process.
Tambunan (2005) found that red fruit seeds can germinate 0.6% after 34 days from the time of planting. Before planting the seeds were soaked in water 100C for 2 minutes and thus immersed in water at room temperature for 24 hours. However, the study found no endocarp layer structure, due to the difficulties of planting using the seeds. Therefore, it is necessary to study the morphological and anatomical structure of the fruit and seeds in order to get understanding of the red fruit seed germination.
2. MATERIALS AND METHODS
The materials (the old and young red fruits) were taken from community garden in Mokwam Village, Minyambouw District in Manokwari Regency West Papua Province. The materials were selected from the best trees that free of pests, old enough and growth well. Thus, we put the materials in a plastic container and label edit. To do morphological and anatomical structure analysis, the fruit was squeezed and washed firstly. The old fruit were dried, while the young seeds were immersed in 70% ethanol. The fruit morphological analyses were analyzed based on the size, color, shape, and texture both the old and young seeds. The anatomical structure were observed microscopically using transverse and longitudinal slices of the fruits and dyed using phloroglucin and 25% HCL to detect wall cell lignifications.
Result showed that P. conoideus Lam. fruit in the form of integrated compound (syncarp) was protected by a bract (braktea) (Figure 1a). Syncarp was red colour with a length of 86-110 cm and width around 30-35 cm (Figure 1b). Syncarp cylindrical was right triangular (Figure 1c) and consisted of many single fruits (drupe) with a length of 1-1.5 cm. The drupe was composed of 3 layers namely exocarp, mesocarp and endocarp enveloping the seed. In the mature drupe, fruit had exocarp that assembles red fruit flesh (Figure 1d). Layer of mesocarp was in the form of fiber (Figure 1e) and endocarp had hard coat like shell (Figure 1f). The top of the drupe was equipped with stigma (Figure 1g). Stigma is easily dislodged when the drupe has matured. Mesocarp pads are on the top cover drupe (Figure 1h and i) and the bottom of the drupe (Figure 1j and k).
Based on the presence of seed parts, the drupe was divided in to drupe with and without embryo (Figure 2a and Figure 2b). Drupe with embryo had a section consisting of seed coat, endosperm and embryo. While drupe seedless had only the seed coat, drupe with embryo when we cut crosswise, it tended to have a rounded shape (Figure 2c). In difference, drupe without embryo tended to have triangle, pentagon and hexagon forms (Figure 2d). The presence of drupe with embryo was found approximately 2% of 500 drupes used as sample.
Anatomical observation on the young and old drupe P. conoideus Lam. showed that there were many cells sklerenkim covered the seed. For instance, in the middle of the young drupe, it showed exocarp, mesocarp and endocarp parts that enveloped the seed (Figure 3a-c). Exocarp contained parenchyma cells. The form of fiber in mesocarp consisted of parenchyma cells and vascular bundles with massive sclerencymatous. Vascular bundles were found in three circles. In the outer circle, it was found that location of the vascular bundles among each other were compact. The inner circle the inner circle, vascular bundles found stretchable. While, in the inner circle, in between vascular bundles. it contained fiber-like sclereids dense and irregular, which was part of the endocarp layer. Endocarp layer will harden when the fruit has matured (Figure 3d & e). The inside of endocarp found tissue, if it be watered formed mucus (mucilaginous). In the young drupe, we found many mucus. In addition, the inner endocarp, mucus is also found in large quantities in a special room at the top of the drupe.
P. conoideus Lam. seed consisted of the seed coat, endosperm and embryo (Figure 4 a). Seed coat was composed by parenchyma cells cube-shaped arranged in two layers (Figure 4b). In the outside of the seed coat, there were lignin cells increasing in number and they toward the embryo to form a blockage such as wings (Figure 4c). Endosperm contained of large cells and had thin walls that contained a lot of starch. Embryos were at the bottom of the drupe, covered by the blockage. Embryo was composed of small dense parenchyma cells (Figure 4d-e). Length embryo measured was 1/6 of the length seed (or smaller), while the width of the embryo was about 1/4 of the width seed.
Essig (1977) reported that the vascular bundles with thin fibrous sheaths encountered vary in length and location. The vascular bundles with thin fibrous elongated sheaths and laid limited in mesocarp which was found in Normanbya and some species of Veitchia. Sheath fiber without vascular bundles (cordons fibreux) inmesocarp also can be found in some species, such as Areca, Cocos, Clinostigma and Alliances.The experiment done by Romanov et al. (2011) showed that the fifth and sixth stages of fruit development in the zone Borassus mesocarp consisted of parenchyma cells containing tannin with thickened walls, fiber-like sclerosis with walls lignified and many vascular bundles with massive sclerencymatous.
Mucus is a matrix that contains pectin in the cell wall will be inflated when it is put in to water. Such cell walls are composed of galacturonic acid not in large numbers with the ability of hydration. The mucus either may or may not contain cellulose microfibrils. In Linum usitatissimun seeds, there is an outer layer of mucus when exposed to water (Fahn, 1995). Martin (1946) classified the embryos in three main types: basal, peripheral and axile. P. conoideus Lam. embryo can be categorized into basal-type embryo. Basal type is characterized by the larger size of endosperm and the small embryo. The embryos shape globular until the oval-oblong. While, cotyledon is usually not perfect and clear, but it can sometimes be seen. The size of seeds ranges frommediumto large size. The basal type embryos can be also found in Magnolia spp., Anemone spp. and Trollius spp seeds.
Red fruit seeds consist of seed coat, endo sperm and embryo. Embryoof red fruit seeds were small and surrounded by a thick endosperm. The thin of red fruit seeds coat surrounded by a blockage, mucilaginous and fruit pericarp.
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