A technological approach to the morphofunctional classification of seedlings of 50 Brazilian forest species. A technological approach to the morphofunctional classification of forest species seedlings defines the essential structures in the evaluation of germination testing and identifies changes in this structures that suggest abnormalities. The objective was to associate morphofunctional seedling classification to seed germination testing using official germination methods for 50 forest species from Amazon, Caatinga, Cerrado, Atlantic Forest and Pantanal biomes. Morphofunctional classification and abnormalities were defined using seedlings from germination pre-tests and 1, samples that were formed for each species using seeds from distinct locations and with at least three levels of vigor.
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A technological approach to the morphofunctional classification of seedlings of 50 Brazilian forest species. A technological approach to the morphofunctional classification of forest species seedlings defines the essential structures in the evaluation of germination testing and identifies changes in this structures that suggest abnormalities.
The objective was to associate morphofunctional seedling classification to seed germination testing using official germination methods for 50 forest species from Amazon, Caatinga, Cerrado, Atlantic Forest and Pantanal biomes. Morphofunctional classification and abnormalities were defined using seedlings from germination pre-tests and 1, samples that were formed for each species using seeds from distinct locations and with at least three levels of vigor.
Common in hypogeal germination, the development of the epicotyl occurred only in seedlings of Anadenanthera colubrina and Erythrina speciosa , both with epigeal germination. The need to supply and sustain the great mass produced in its long life cycle, the presence of the primary root was considered essential for the normal seedling classification of these forest species. Curled, stunted, necrotic, bifurcated primary root and those retained in the seed coat or in the fruit structures, were the main abnormalities of the seedling root systems.
Damages to the shoot system were uncommon. Index terms: abnormal seedlings, epigeal germination, hypogeal germination, tropical specie. Germination measurements such as capacity, time, velocity, synchrony and uniformity contribute to the understanding of the germination process Ranal and Santana, Nevertheless, these same measurements are dependent on experimental conditions during germination testing and thus cannot be used to group species.
In contrast, conservative characteristics such as seedling morphology and structural functionality do make it possible to organize classification systems Miquel, ; Garwood, In this context after conducting a floristic survey of the tropical forest tree species from Panama, Garwood ; symbolized five seedling classifications of Miquel , categorizing cotyledons based on exposure, position, texture and function during germination.
Some seedling types occur in Brazilian biomes, especially from Amazon that were not described by these authors Ressel et al. Thus, Miquel's classification has been expanded Ferraz and Calvi, The most common approach to seedling classification is ecological and aimed at understanding the function of structures during seedling establishment and developement.
Although uncommon, the technological classification of forest species is indespensable for defining essential seedling structures during germination testing. Moreover, technological classification improves the precision of inferences about abnormalities because it identifies abnormal structural changes. Thus, the objective was to associate morphofunctional seedling classification to seed germination testing using official germination methods for 50 forest species from Amazon, Caatinga, Cerrado Atlantic Forest and Pantanal biomes.
The germination test methods for 50 species Table 1 were officialized by the Brazilian Ministry of Agriculture and Food Supply Brasil, ; ; The 50 species seedling were classified, sensu Ferraz and Calvi , by cotyledon exposure cryptocotylar and phanerocotylar , and hypocotyl development hypogeal and epigeal.
Each species was morphofunctionally classified using seedlings from germination pre-tests with 1, samples. Samples of each species consisted of seeds collected from different locations provenances and with at least three vigor levels.
The first seedling count was based on high-vigor seeds and the last count was based on low-vigor seeds. Some species also required intermediate countings. Seedling shoots were qualitatively evaluated between five and 30 days after sowing. Seedling abnormalities were identified using the defined morphological structures of each species and essentiality criteria.
Particularities in seedling morphology were identified, recorded and excluded from the classification of abnormal seedlings. Most of the seedlings of these 50 forest species had cotyledons that were detached from the seed coat or the epicarp phanerocotylar , developed hypocotyl epigeal and non-developed epicotyl Table 1.
The prevalence of phanero-epigeal seedlings is not restricted to this group of 50 Brazilian forest species. In Brazil, the highest frequency of this type of seedling was encountered in areas from Amazon Forest Maia et al. Only one species had cryptocotylar seedling germination and six had hypogeal germination Table 1 , indicating the low occurance of these seedling types. Indeed, hypogeal and cryptocotylar seedlings are less frequent in tropical forests Wright et al.
Although, most species with cryptocotylar seedlings have hypogeal germination, there are exceptions Wright et al. Regarding the exposure of the cotyledons, some seedlings showed intermediate behavior. Phanerocotylar seedlings of Ormosia arborea Vell. Harms and Peltogyne confertiflora Hayne Benth. Peltogyne confertiflora cotyledons were exposed through small cracks in the seed coat Figure 1d. Cotyledon position relative to the soil due to hypocotyl development is not restricted to epigeal and hypogeal germination types Miquel, ; Garwood, ; Ferraz and Calvi, Intermediate types such as the semi-hypogeal have been recorded for seedlings of some species that present detached cotyledons phanerocotylar , remain at soil level and are not elevated by the hypocotyl Miquel, ; Milanez et al.
This type of development has been observed in Anadenanthera macrocarpa Benth. Brenan seedlings Ressel et al. According to phylogeny, cogeneric species should have the same morphofunctional classification Garwood, Nevertheless, Anadenanthera colubrina Vell. Brenan and Anadenanthera macrocarpa seedlings showed epigeal and hypogeal or semi-hypogeal germination, respectively Table 1.
This same distinction was found in species of the Jacaranda genus. Developed epicotyls were a characteristic of epigeal seedlings of Anadenanthera colubrina, and Erythrina speciosa Andrews Figures 2a , b , however they were uncommon for the other species with epigeal germination Table 1. All hypogeal seedlings had developed epicotyls Figures 2d , e except for Pseudobombax tomentosum Mart.
Robyns Figure 2f. In this specie, cotyledon elevation is caused by cotyledonary petioles. Because these petioles carry out the function of the hypocotyl, the germination was classified as epigeal for Ressel et al. Seedlings with hypogeal germination have developed epicotyls Wright et al.
Primary root essentiality was the only subjective classification used because it was impossible to predict which environmental conditions cause secondary roots to assume the role of absent or deficient primary roots.
The presence of the primary root was considered essential to classification as normal seedling. Strongly developed secondary roots in seedlings of Erythrina speciosa occurred only when the primary root was already developed.
The primary root was considered one of the most important categories of the importance that the root system has to supply the plant with water and nutrients to sustain the great mass produced during the long life cycle of these forest species. Regardless of biome, secondary roots are common in hypogeal or semi-hypogeal seedlings. This suggests that secondary roots may not be essential for seedling with these characteristics. However, primary root essentiality in this seedling category occurs when a species develops tuberous roots as in Amburana cearensis Arr.
Smith Ramos et al. The major abnormalities in seedlings were curled Figure 3a , stunted Figures 3b , d , e , f , bifurcated Figure 3c primary roots and primary roots retained in the seed coat Figures 3a , g or retained in the floral calyx Figure 3h. The extensive root structures in these 50 forest seedlings, at the expense of shoot development, preserved structures such as cotyledons, hypocotyls and epicotyl.
The only abnormality found in the epicotyl was its absence in hypogeal seedlings and in the three species possessing epigeal germination and developed epicotyls Anadenanthera colubrina and Erythrina speciosa. Seedlings of this species had cryptocotylar germination in which the cotyledons were collapsed against the seed coat, unremoveable and indistinguishable from it. Some characteristics considered abnormal in agricultural species are frequent and thus considered normal in some of these forest species.
These characteristics include darkened pigmentation in the cotyledons of Dalbergia miscolobium , darkened pigmentation in the root system of Astronium fraxinifolium epicotyl and eophylls were also pigmented , Copaifera langsdorffii and Lafoensia pacari A. Ravenna , Enterolobium contortisiliquum Vell.
Morong, Hymenaea stigonocarpa and Ormosia arborea seedlings. While morphofunctional classification is useful for evaluating germination tests, it should be remembered that forest species are more prone to phenotypic plasticity than agricultural species. Environmental heterogeneity, seasonal change and the influences of temperature, precipitation photoperiod and resource availability can cause significant plasticity Chambel et al.
The forest species are comprised in several botanical families and thus morphological variations of seeds and seedlings are larger than the agriculture species. Because forest species are long-lived, small seedling defects can be overcome Ferraz and Calvi, Consequently, the classification requirements for agricultural species should not be extended to forest species.
Despite lower requirements for forest seedlings, the same level of quality is sought for forest and agricultural seedlings. During seedling establishment, forest species are exposed to more pathogens, herbivores, habitat alteration, competition among species and anthropogenic factors Sarmento and Villela, Moreover, measuring the capacity of developing into a mature plant is only predictive.
According to the technological approach to morphofunctional classification during the germination test, normal seedlings with phanero-epigeal germination should have free cotyledons and a developed hypocotyl.
Besides these features, the epicotyl should also be developed in Anadenanthera colubrina and Erythrina speciosa seedlings;. In the germination test, normal seedlings with phanero-hypogeal germination must have free cotyledons and a developed epicotyl. For this classification there are exceptions for Pseudobombax tomentosum seedlings for not having developed epicotyls and Astronium fraxinifolium seedlings with pericarp attached to the cotyledons cryptocotylar ;.
In the evaluation of the germination test, the presence of the primary root for the seedlings of the 50 species is essential for obtaining a normal seedling classification. Susceptibility of tree seedlings to biotic and abiotic hazards in the understory of a moist tropical forest in Panama. Biotropica , v. Seed size, seedling morphology, and response to deepshade and damage in neotropical rain forest trees.
American Journal of Botany , v. Manaus: INPA, Phenotypic plasticity: a useful framework for understanding adaptation in forest species. Seed germination in a seasonal tropical forest in Panama: a community study.
Ecologycal Monographs , v. Functional morphology of tropical tree seedlings. Paris: Parthenon, Post-establishment seedling success in the Brazilian cerrado: a comparison of savanna and forest species.
Seedling functional types in a lowland rain forest in Mexico. ISTA Handbook on seedling evaluation. Bassersdorf: International Seed Testing Association, ISTA Method validation for seed testing. Seedling morphology of non-pioneer trees in central Amazonian varzea floodplain forests. Ecotropica , v. Semi-hypogeal germination in Pachyrhizus ahipa Wedd.
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