Deforestation in the Amazon Basin is still increasing, and the rehabilitation of these lands continues to be a challenge. Autoecological studies of most Amazonian species are rare, and efficient techniques for restoration of forested habitats have yet to be developed. The aim of this study was to test direct sowing as a rehabilitation technique for sites with different degrees of disturbance: bare soil, pasture, and secondary and mature forests in Central Amazonia, Brazil. At each site, we sowed seeds of 11 native tree species. Throughout the following year we evaluated germination and seedling survival. The germination differed according to the study site and species. Seedling survival in degraded sites was higher than in other areas. After 1 year in the bare soil site, 33% of the sown seeds of eight species developed seedlings; in the pasture the establishment was 23%, in secondary forest 15%, and in mature forest 12% of only four species. The only widespread survivor with more than 45% emergence in all perturbed sites was Caryocar villosum. No pioneer seedlings remained after 1 year. There was a positive correlation between seed size and survival. Large-seeded non-pioneer species seem to be more suitable for direct sowing than small-seeded species. We recommend a combination of direct sowing and planting of seedlings as an appropriate means to accelerate the rehabilitation of degraded areas in Central Amazonia.

Rehabilitation of Degraded Areas of Central Amazonia Using Direct Sowing of Forest Tree Seeds

Seed germination of herbaceous and woody species of the Sudanian savanna-woodland in response to heat shock and smoke

The present study had the objective of developing a non-conventional method to determine mechanical damage in soybean seeds, and also to verify its relation to the physiological quality, using the image analysis technique. Unlike the traditional tests, this technique analyzes seeds without destroying them, and together with the germination test, it can be observed that the damage detected in the image analysis is really important because of its influence on the germination process. The research was carried out with three cultivars of soybean (FT-2, FT-10 and IAC-2), possessing different contents of lignin in the seed coat (different resistance performance for mechanical damage). The mechanical damage had been caused by means of the pendulum test in six different regions of the seeds. The image analysis identified external and internal mechanical damage in soybean seeds, and was also efficient in detecting weathering and stink-bug damage.

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Avaliação de danos mecânicos em sementes de soja por meio da análise de imagens

'Aroeira-branca', an arboreal species of great ecological and economic importance, is seed propagated and presents limitations with respect to the availability of methods for seed quality evaluation. The X-ray test has been considered of potential value because it is accurate, quick and nondestructive. In this context, the objective of this work was to verify the possibility of this test to detect damage and/or abnormalities in aroeira-branca embryos, in an attempt to correlate these anomalies to germination. Four seed lots were collected in different locations in the southern region of the State of Minas Gerais, Brazil, during 2001. The X-ray test consisted of submitting 100 seeds/lot to radiation (exposure of seeds to radiation of 13 kV/5 minutes) and classifying them according to embryo/embryo cavity proportions of 0, < 50, 50-75 and 100%, with the latter class divided into normal and abnormal according to embryo morphology. The germination test was then carried out to detect possible relationships between seed anatomy and the resulting seedling/seed ratio, as revealed by radiographs. Seeds presenting an embryo/embryo cavity proportion lower than 100%, as determined by the X-ray test, did not germinate, and those presenting abnormal embryos produced abnormal seedlings or did not germinate, providing evidence that the X-ray test is effective to assess seed quality.

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'Aroeira-branca' [Lithraea molleoides (Vell.) Engl. - Anacardiaceae] seed quality evaluation by the X-ray test

Visgueiro is a neo-tropical tree species with economic and ecologic importance. This work aimed to determine the imbibition time and moisture content of P. pendula seeds necessary to activate metabolism and improve their performance by priming. Stored seeds (2 years) and unstored seeds (7 days) were compared. After clipping, the seeds were kept in water at 15 oC for periods of 4 to 28 hours to reach the desired imbibition degrees (20, 40, 60, 80 and 90%). Seeds were then sown immediately in washed sand in the nursery (4 x 25 seeds / treatment) or dried for 7 days (24±2°C and 68±3% R.H.). Unstored and unprimed (control) seeds showed 59±8.9% germination, which was less than that of stored unprimed seeds (76±11.3 %). Submersion periods exceeding 13 hours reduced germination relative to unprimed seeds. After 4 hours of submersion (seed moisture 26-31%), both unstored and stored seeds increased their performance. Even higher improvement was verified when drying followed submersion. Thus, the positive effects of priming occurred in phase I of the imbibition curve. Hydropriming of 4 hours at 15 oC was found to be a simple and inexpensive method for P. pendula seeds since it increased seedling development velocity, brought the germination percentage of unstored seeds to a level similar to that of stored seeds and increased germination synchronization of stored seeds.

https://www.scielo.br/pdf/rarv/v32n1/06.pdf

K. M. Poulsen

Papers

ISTA tropical and sub-tropical tree and shrub seed handbook.