Alfredo Gui Ferreira

Germinação de sementes de Asteraceae nativas no Rio Grande do Sul, Brasil

Achenes of thirteen native Asteraceae species common to the natural grassland or weeds of the southern region of Brazil were tested for germination over a range of alternating temperatures ( 20/10; 25/15; 30/20 and 35/25°C), and under constant temperatures ( 20; 25 and 30°C) with light or not .Only fresh collected achenes (herein = seeds) were used. The optimum temperature for germination differed among the species, with Elephantopus mobillis; Eupatorium laevigatum; Mikania cordifolia; Senecio oxyphyllus; Trixis praestans germinating the most over all temperatures tested. Eclipta alba seeds germination was promoted at 30°C. Colder treatments promoted germination in Tagetes minuta , and in Senecio heterotrichius; S.selloi; Stenachaenium campestre; Symphyopappus casarettoi and Vernonia nudiflora germination was equivalent at 20 or 25°C. Light promoted germination for all species except in Stenachaenium campestre and Tagetes minuta, the latter being a negative photoblastic species. According to the mean time for germination, the species could be ranked in: fast -less than 5 days- (Baccharis trimera; Eclipta alba; Elephantopus mollis; Stenachaenium campestre and Vernonia nudiflora); intermediate: between 5 and 10 days- (Eupatorium laevigatum; Mikania cordifolia and Tagetes minuta) ; slow: more than 10 days-(Senecio heterotrichius; S.oxyphyllus; S.selloi; Symphyopappus casarettoi; Trixis praestans). The results show that germination of seeds of a range of Asteraceae species varies with temperature and light regime; they provide an initial basis on which to test and interpret the effects of seasonal factors on germination and field establishment. In addition, comments on the agar and sand substrates were made.

Germinação de sementes de plantas medicinais lenhosas

Seed germination of Aloysia gratissima, Bauhinia forficata; Casearia sylvestris, Dodonea viscosa, Psychotria leiocarpa e Sida rhombifolia was verified using agar at 1% in petri dishes or sand, as substrate. The germination was tested under constant temperatures of 20°C, 25°C, 30°C and 35°C in light or darkness, and also at 10°C and 15°C in the dark. Morever, diary alternating temperatures of 10-20°C; 15-25°C; 20-30°C and 25-35°C were used, the higher temperature being in light at a radiating intensity of 40 to 60 µmol.m-2.s-1. Only A. gratissima showed positive photoblastic behavior, but higher germination was found at alternating temperatures. Both, C. sylvestris and P. leiocarpa at constant temperatures germinated only at 20 or 25°C. B. forficata seeds germinated more than 80% from 15°C to 30°C constant or when one of the shift temperatures was on that range. Scarified seeds of D. viscosa germinated at the same level from 10°C to 35°C. S. rhombifolia seeds germinated in higher rates at the constant temperature of 35°C or the alternating ones that included 35°C in the treatment. The higher percentage of germination achieved was from 44% in A. gratissima to 97% in B. forficata seeds. Since those are native species about which there are no reports on genetic improvement or landrace selection, the percentages of germination obtained were considered acceptable.

Atividade de peroxidase e polifenoloxidase na resistência do feijão à antracnose

The objective of this work was to evaluate the influence of peroxidase and polyphenol oxidase enzymes in anthracnose resistance of four bean cultivars. Seedlings were sprinkled with salicylic acid and delta race of Colletotrichum lindemuthianum (inducer fungus) and after three days they were inoculated with 33/95 virulent pathotype of C. lindemuthianum. Enzyme activity and phenol levels were evaluated three days after inducer fungus application and five days after inoculation with virulent pathotype. Plants treated with salicylic acid and inducer fungus presented higher activity increases of both enzymes, in all cultivars. Higher impulses in enzymatic activity were observed in cultivars with higher disease resistance. One isoperoxidase appeared in treatments with inducer fungus, salicylic acid, after inoculation with virulent pathotype, and in control plants, in AB 136, Rio Tibagi and Macanudo cultivars. Positive correlation was observed among peroxidase and polyphenol oxidase activity, phenolic compound levels and anthracnose resistance.

Induction of chalcone synthase and phenylalanine ammonia-lyase by salicylic acid and Colletotrichum lindemuthianum in common bean

The activities of the enzymes chalcone synthase (CHS) and phenylalanine ammonia-lyase (PAL) were measured in leaf extracts obtained from four cultivars of the common bean (AB 136, Rio Tibagi, Carioca and Macanudo). Two stages of plant development were examined: plantlets (V2) and the onset of blooming (R6). Initially, the plants were either treated with salicylic acid or inoculated with the delta race of Colletotrichum lindemuthianum (inductive fungus) and after three days they were evaluated for enzyme activity. Afterwards, all plants were inoculated (challenged) with the virulent pathotype 33/95 of C. lindemuthianum except for the water control. Five days later, the activities of PAL and CHS were evaluated. There were significant changes in the activities of both enzymes three days after treatment with salicylic acid or inductive fungus when compared to the control. Five days after inoculation with with the virulent pathotype 33/95 of C. lindemuthianum CHS activity in the Macanudo was similar to control plants that were not treated with salicylic acid or the inductive fungus but inoculated with 33/95 C. lindemuthianum. The increase in enzyme activity after challenge with 33/95 C. lindemuthianum was greatest for the salicylic acid treatment in the cultivar AB 136, followed by Rio Tibagi and Carioca.

Características de frutos e germinação de sementes de seis espécies de Myrtaceae nativas do Rio Grande do Sul.

Myrtaceae family is well represented in the flora of Rio Grande do Sul, in the Southern region of Brazil. The seed and the fruits from six trees species of this family were examined concerning their size, color, mass and water content. The species were the following: Acca sellowiana (Berg.) Burnet; Campomanesia guazumifolia (Camb.) Berg.; Campomanesia xanthocarpa Berg.; Eugenia rostrifolia Legr.; Myrcianthes pungens (Berg.) Legr and Psidium cattleyanum Sabine. The germinative behavior of the seeds was evaluated and the substratum used was autoclaved, which was placed in gerbox (11 x 11cm), at constant temperatures 15, 20, 25 or 30°C or in alternate ones 15°C/ 30°C, with fourteen hours period, in the highest temperature. The experiments were also carried out in the dark. The seeds of Acca sellowiana , Myrcianthes pungens , Psidium cattleyanum showed positive photoblastic behavior. All species germinated in 90 days except Campomanesia guazumifolia which took around 150 days to germinate. The water content ranged from 9% in Campomanesia guazumifolia to 68% in Myrcianthes pungens and the seeds varied from intermediate to recalcitrant ones. The eugenoid embryos had a cryptocotylar germination, however the myrciod and the pimentoid had a fanerocotylar germination.

Allelopathic effects of aqueous extracts of Artistolochia esperanzae O.Kuntze on development of Sesamum indicum L. seedlings

Aristolochia esperanzae is a climbing plant that occurs in the savanna regions of Brazil. The aim of this work was to identify the effects of aqueous extracts of A. esperanzae on germination, root growth and xylem cell development of sesame seedlings. Leaf and shoot extracts were prepared at concentrations of 1.5 and 3%. Extracts caused marked changes in germination and seedling growth with greatest inhibition produced by root extracts. Morphological changes and decreased growth and development of seedlings were also observed. The extracts of A. esperanzae caused a reduction of 50% in the size of root xylem cells and marked changes in the primary root and in the number of secondary roots.

Efeito alelopático de folhas de Solanum lycocarpum A. St.-Hil. (Solanaceae) na germinação e crescimento de Sesamum indicum L. (Pedaliaceae) sob diferentes temperaturas

Allelopathy should be defined as any stimulatory or inhibitory effect by one plant on another through production of chemical compounds released into the environment. Several Solanum species have shown some allelopathic property. S. lycocarpum islargely distributed on disturbed areas of the Brazilian Cerrado. In the present study the effects of aqueous extracts of S. lycocarpum leaves on the germination and growth of Sesanum indicum L. (sesame) were investigated. Aqueous leaf extracts at concentrations of 1%, 2%, 3%, 4%, and 5% (w/v) were prepared. The osmolarity of the extracts were measured and solutions of polyethylene glycol (PEG 6000) of similar osmolarity were prepared to evaluate osmotic effects of the extracts on sesame germination and growth. The experiments were carried out on petri dishes lined by two layers of filter paper plus the solutions to be tested. For the germination experiments the number of germinated seeds was checked every 8h. For the growth experiments sesame seeds were previously germinated in water and disposed to grow in the extracts. After five days of incubation the root and shoot length of the seedlings was measured. All the experiments were performed at 22 oC, 30 oC and 38 oC. The extracts did not affect the germinability but increased the average germination time in a dose-dependent manner at the three temperatures. The root growth was more affected by the extracts, showing tip-necrosis, absence of root hairs, and formation of secondary roots. These effects were more evident at 38 oC. Using PEG 6000 it was shown that the observed effects were not due to osmotic properties of the leaf extracts.

Efeito alelopático de folhas e frutos de Solanum lycocarpum A. St.-Hil. (Solanaceae) na germinação e crescimento de Sesamun indicum L. (Pedaliaceae) em solo sob três temperaturas

Investigaram-se os efeitos de extratos aquosos de folhas e frutos de Solanum lycocarpum na germinacao e crescimento inicial de Sesamum indicum em solo. Os experimentos foram conduzidos sob temperaturas de 22, 30 e 38 oC. O extrato de folhas nao interferiu significativamente no tempo medio, mas reduziu a germinabilidade e diminuiu o pico de germinacao nas tres temperaturas. Esse extrato nao interferiu significativamente no crescimento da parte aerea, exceto a 30 oC, mas reduziu significativamente o crescimento da radicula nas tres temperaturas. Os extratos de frutos aumentaram significativamente o tempo medio de germinacao a 30 oC e reduziram a germinabilidade a 22 oC. Tambem reduziram tanto o crescimento aereo quanto das raizes das plântulas. Os resultados mostram que as propriedades alelopaticas de Solanum lycocarpum se manifestam no substrato solo em ampla faixa de temperatura.

Seed disinfestation methods for in vitro cultivation of epiphyte orchids from Southern Brazil

Disinfestation of orchid seeds is necessary when the germination is performed in vitro. In such case, cultures are supplemented by a source of sugar and salts in order to obtain energy and other requirements. However, the presence of sugar and salts easily allows the development of unwanted microorganisms. To avoid such phenomenon, an efficient procedure must be done as a pretreatment of the seeds with liquid or gaseous substances. In this study with several Brazilian orchids, the seeds were disinfested with sodium hypochlorite solutions containing 0.4% or 0.8% active chlorine for five minutes and sodium hypochlorite or formaldehyde fumes up to two hours, this procedure being efficient for such purpose and making it possible to be used routinely.

Germinação de sementes de espécies medicinais do Rio Grande do Sul: Bromelia antiacantaha Bert., Cuphea carthagenensis (Jacq.) Macbride e Talinum patens (Jacq.) Willdenow

These species of herbs are well distributed over all Rio Grande do Sul State, and are used to prepare medicine for the human population. The influence of constant temperatures (10oC; 15oC; 20oC; 25oC; 30oC and 35oC) on the germination of seeds during a photoperiod of 8 hours, was analyzed. Experiments were also performed in darkness, and at alternating temperatures (10-20oC; 15-25oC; 20-30oC; 25-35oC). Seeds that did not germinate were submitted to the tetrazolium test. Over 80% of the seeds of B. antiacantha germinated at constant temperatures of 25o, 30o or 35oC, both in light and darkness. Below 25oC, the seeds presented relative dormancy. Storage during one year under laboratory conditions (25oC), or at a low temperature (5oC) allowed for 90% of seed viability. Over 80% of the seeds of C. cartliagensis germinated at alternating temperatures, but no germination was observed at constant temperatures, although the seeds remained viable. T. patens presented over 50% of deteriorated seeds and final germination was similar at constant and alternating temperatures. The three species can be propagated through seeds, if the appropriate temperature requirements are observed for each of them.