Morphophysiological changes of Acca sellowiana (Myrtaceae: Myrtoideae) saplings under shade gradient / Alterações morfofisiológicas em mudas de Acca sellowiana (Myrtaceae: Myrtoideae) sob gradiente de sombreamento

Abstract Understanding morphological and physiological changes under different light conditions in native fruit species in juveniles' stage is important, as it indicate the appropriate environment to achieve vigorous saplings. We aimed to verify growth and morphophysiological changes under shade gradient in feijoa (Acca sellowiana (O. Berg) Burret) to achieve good quality saplings adequate to improve cultivation in orchards. The saplings were grown for twenty-one-month under four shading treatments (0%, 30%, 50%, and 80%). Growth, photosynthetic pigments, gas exchanges, chlorophyll fluorescence, and leaf anatomy parameters were evaluated. Saplings under full sun and 30% shade had higher height and diameter growth and dry mass accumulation due to higher photosynthesis rate. As main acclimatization mechanisms in feijoa saplings under 80% shade were developed larger leaf area, reduced leaf blade thickness, and enhanced quantum yield of photosystem II. Even so, the net CO2 assimilation and the electron transport rate was lower and, consequently, there was a restriction on the growth and dry mass in saplings under deep shade. Therefore, to obtain higher quality feijoa saplings, we recommend that it be carried out in full sun or up to 30% shade, to maximize the sapling vigor in nurseries and, later, this light environment can also be used in orchards for favor growth and fruit production.

Resumo A verificação de mudanças morfológicas e fisiológicas sob diferentes condições luminosas em espécies frutíferas nativas em estágio juvenil é importante, uma vez que indicam o ambiente adequado para a formação de mudas com alto vigor. Objetivou-se verificar o crescimento e as alterações morfofisiológicas sob gradiente de sombreamento em mudas de feijoa (Acca sellowiana (O. Berg) Burret) para obter mudas de boa qualidade, adequadas para fomentar os plantios da espécie em pomares. As mudas foram cultivadas por vinte e um meses sob quatro tratamentos de sombreamento (0%, 30%, 50% e 80%). Foram avaliados parâmetros de crescimento, pigmentos fotossintéticos, trocas gasosas, fluorescência da clorofila e anatomia foliar. Mudas a pleno sol e 30% de sombra apresentaram maior crescimento em altura, diâmetro e acúmulo de massa seca, devido à maior taxa de fotossíntese. Como principais mecanismos de aclimatação sob 80% de sombra, as mudas desenvolveram maior área foliar, redução da espessura do limbo foliar e aumento do rendimento quântico do fotossistema II. Mesmo assim, a assimilação líquida de CO2 e a taxa de transporte de elétrons foram menores e, consequentemente, houve restrição ao crescimento e acúmulo de massa seca das mudas no maior nível de sombreamento. Portanto, para a obtenção de mudas de feijoa de maior qualidade, recomendamos que seja realizada a pleno sol ou até 30% de sombra, para maximizar o vigor das mudas em viveiros e, posteriormente, este ambiente de luz também pode ser utilizado em pomares para favorecer o crescimento e a produção de frutos.

Effect of essential oils on the development of Colletotrichum sp. fungus in fragments of Feijoa sellowiana fruits

The aim of this work was to evaluate the effect of the essential oils of Syzygium aromaticum, Cymbopogon citratus, Eucalyptus citriodora and Rosmarinus officinalis on the mycelial development of the fungus Colletotrichum sp. in fragments of Feijoa sellowiana fruits. The essential oils were incorporated in the PDA (Potato-Dextrose-Agar) medium in the concentrations of 250, 500 and 1000 ppm, 0 ppm (PDA only) (negative control), and fungicide fluazinam 1% (positive control). The area under the mycelial growth curve (AUMGC) and percent inhibition of mycelial growth (PIMG) were calculated. In the second evaluation, fruits fragments bordering the disease symptom were immersed in essential oils aqueous solution of S. aromaticum, C. citratus, and E. citriodora, at the concentration of 5000 ppm, 0 ppm (water only - negative control) and fluazinam 1% (positive control). The immersion times in the treatments were: 2, 4, 8, 12 and 24 hours, with subsequent incubation in Agar-Agar medium at 25°C. This evaluation was performed daily for 15 days, observing the moment of fungal germination through the emission of the mycelium. It was verified from the obtained results that all treatments reduced the fungal growth, and the essential oils of C. citratus and S. aromaticum totally inhibited its growth from the dose 500 and 1000 ppm, respectively. Regarding the test on fruit fragments, the essential oil of S. aromaticum at the immersion times of 12 and 24 hours was effective in inhibiting the fungus until the 15th day of evaluation.

Petiscos florais: pétalas de Acca sellowiana (Myrtaceae) como fonte alimentar para aves em área urbana no Sul do Brasil / Floral titbits: petals of Acca sellowiana (Myrtaceae) as a food source for birds in an urban area in Southern Brazil

A goiaba-serrana (Acca sellowiana, Myrtaceae) é uma das poucas espécies vegetais cujas pétalas são habitualmente usadas como alimento por aves nos Neotrópicos. Registramos aqui o consumo de pétalas desta mirtácea por nove espécies de aves Passeriformes, numa arvoreta isolada em área urbana de Gramado, Rio Grande do Sul. A maior freqüência de visitas foi registrada para espécies de Thraupidae, aves predominantemente frugívoras. As aves tomavam as pétalas entre as mandíbulas e arrancavam ou cortavam porções, deixando sinais característicos nas flores. Thraupis sayaca e Tangara preciosa foram registrados recolhendo porções de pétalas e levando-as entre as mandíbulas, a primeira espécie tendo sido duas vezes observada fornecendo pétalas a ninhegos. Devido ao seu porte médio e à beleza das suas flores, bem como à atração de diversas espécies de pássaros mesmo em área urbanizada, reiteramos aqui o uso de A. sellowiana em arborização urbana no Sul e Sudeste do Brasil.

The feijoa (Acca sellowiana, Myrtaceae) is one of the few plant species whose petals are habitually eaten by birds in the Neotropics. We record here the use of petals of this myrtaceous plant by nine species of passerine birds of an isolated plant in the urban area of Gramado, Rio Grande do Sul, southern Brazil. Highest visiting frequency was recorded for tanagers (Thraupidae), a predominantly frugivorous bird group. The birds took the petals within their mandibles and tore or cut pieces off. Thraupis sayaca and Tangara preciosa were recorded collecting several petal pieces with their mandibles, the first species being observed twice feeding petals to nestlings. Due to its medium size and the showy flowers, as well as to its attractiveness to several bird species even in an urbane area, we reiterate here the recommendation to use A. sellowiana in parks and gardens in southern and southeastern Brazil.