Phytotoxic Activity of Parthenium Against Wheat and Canola Differ With Plant Parts and Bioassays Techniques

Phytotoxic effects of invasive weed Parthenium hysterophorus were studied by using whole plant, leaf and root aqueous extracts at 0, 2.5, 5.0, 7.5 and 10% (w/v) concentrations against germination and early seedling growth of wheat and canola. Studies were carried out both in Petri plates with filter paper as substratum placed in controlled conditions and soil-filled plastic pots placed in open environments. Pronounced variation was noted for phytotoxic activity of different plant parts of parthenium, aqueous extract concentrations, test species, and bioassay techniques. Aqueous parthenium extracts either inhibited or delayed the germination and suppressed seedling growth of test species over control. For both test species, all the germination attributes were suppressed to a greater extent in Petri plates than in plastic pots. Leaf extracts were more suppressive to germination of test species than whole plant and root extracts. Increasing extract concentration beyond 2.5% caused significant reduction in seedling dry biomass of both test species. Aqueous parthenium extract diminished chlorophyll contents of wheat and canola by 32-63% and 29 69%, respectively. Nevertheless, an increase of 9-172% and 22-60% in phenolic contents of wheat and canola was recorded. Canola appeared to be more susceptible than wheat at all extract concentrations. Present study concluded that bioassays conducted under controlled condition using filter paper as substratum may be misleading due to over estimation of allelopathic response and variation in potential of receiver and donor species. Furthermore, it implies that threshold concentrations of allelochemicals for test species in Petri plates are rarely reached under field conditions.

Exploring Herbicidal Potential of Aqueous Extracts of Some Herbaceous Plants Against Parthenium Weed

To assess the phytotoxic potential of Achyranthes aspera, Alternanthera philoxeroides, Datura metel and Rumex dentatus against Parthenium hysterophorus, 5% (w/v on dry weight basis) aqueous extracts from root, stem, leaf, flower and whole plant were tested through a Petri plate-based germination and pot-cultured seedling bioassays. Achyranthes aspera and A. philoxeroides inhibited parthenium weed germination more than extracts from other species. Whole plant, leaf and fruit extracts of A. aspera reduced the germination percentage (5%); leaf extract from A. philoxeroides caused lower germination index (0.4), higher mean germination time (14 d) and longer time to 50% germination (13.5 d) of parthenium weed. In the foliar spray bioassay, A. aspera reduced parthenium weed shoot growth more than the other species whereas R. dentatus caused more reduction in root growth. Whole plant extract from A. aspera caused maximum reduction in parthenium weed seedling vigor index (98%) and seedling biomass (96%). The aqueous extracts of A. aspera and A. philoxeroides contained higher concentrations of phenolics viz. gallic (16.9 mg L-1), caffeic (7.4 mg L-1), chromatotropic (63.8 mg L-1), p-coumaric (10.5 mg L-1), m-coumaric (3.1 mg L-1), syringic (9.21 mg L-1) and 4 hydroxy-3-methoxy benzoic (118.6 mg L-1) acids compared with extracts of the other two species tested.

Comparative uptake and metabolism of 2-[14C]-2,4-dichlorophenoxyacetic acid in callus cultures of monocot (Dioscorea spp.) and dicot (Nicotiana tabacum L.) plants

(Comparative uptake and metabolism of 2-[14C]-2,4-dichlorophenoxyacetic acid in callus cultures of monocot (Dioscorea spp.) and dicot (Nicotiana tabacum L.) plants). The uptake and metabolism of 2-[14C]-2,4-dichlorophenoxyacetic acid (2,4-D) were investigated in leaf calluses of Nicotiana tabacum, tuber calluses of Dioscorea opposita and calluses derived from zygotic embryos, leaves and petioles of Dioscorea composita. Striking similarities were evident in the patterns of 2,4-D metabolites and their chemical characteristics in the three callus types of D. composita compared, but significant differences were detected among the patterns of rnetabolites in the three species studied. Preliminary investigations on the stability of various metabolites (separated using TLC) by hydrolysis showed that sugar esters appeared to be the major metabolites in tobacco whilst in yams (D. opposita) glycosides were shown to be the main ones, which indicated a similarity between plants of Gramineae and Dioscoreaceae in terms of 2,4-D metabolism. Release of 2,4-D from tobacco callus cells upon their transfer to 2,4-D-free medium was detected and the implications of this are discussed in relation to the cultural conditions necessary to induce morphogenesis in vitro.

Effect of light and temperature on germination and early growth of Vochysia tucanorum Mart., Vochysiaceae, in cerrado and forest soil under different radiation levels

Vochysia tucanorum Mart. (Vochysiaceae) is a very widely distributed species in the cerrado and forests in Brazil, from the State of Bahia to Paraná. Its seed germination was analysed under eight treatments using different conditions of light and temperature. Up to 73 days, at least ca. 93% of the seeds germinated in all treatments, except under alternating temperatures of 35°/10°C (62%). Light enhanced germination, except under constant temperature of 25°C when seeds are not photoblastic. At this temperature, the highest percentage of germination was found. Initial vegetative growth was analysed by comparing the effects of shading, by means of different percentages of full daylight (100%, 45%, 10.6%, 4.8%), and soils from cerrado and forest. During 123 days, no mortality was recorded and cotyledons persisted on the seedlings of all treatments. In general, the seedlings of V. tucanorum were found to be more or less indifferent to the soil from cerrado or forest and shading seems to promote height increment. However, total dry mass was larger under a radiation of 45% full daylight and smaller under extreme conditions (100% or 4.8% full daylight).

Efeito da temperatura na germinação de sementes e morfologia da plântula de Maquira sclerophylla (Ducke) C.C. Berg

Maquira sclerophylla é uma árvore de interesse econômico madeireiro, encontrada na floresta de terra firme por toda a bacia Amazônica. Os objetivos deste trabalho foram estudar a morfologia do fruto, da semente e da plântula e observar o efeito de temperaturas constantes entre 10 e 35°C na germinação e formação de plântulas. Os frutos de M. sclerophylla são pseudodrupas globosas contendo uma grande semente também globosa, que representa cerca de 80% da massa fresca do fruto. A germinação é semi-hipogea e fanerocotiledonar, com cotilédones carnosos e viridiscentes. A emergência da radícula ocorreu nas temperaturas entre 15 e 35°C, porém, o desenvolvimento da plântula normal foi observado somente entre 20 e 30°C. Os resultados indicam 30°C como temperatura ótima para a germinação das sementes. Nesta condição, a emergência da radícula ocorreu após 18 dias, em média, e a formação da plântula com raiz primária, epicótilo e o primeiro par de folhas desenvolvidas, cerca de 37 dias após a semeadura.

Morfogênese in vitro e susceptibilidade de calos de variedades nacionais de cana-de-açúcar (Saccharum officinarum L.) a agentes seletivos utilizados em sistemas de transformação genética

Foi avaliada a morfogênese in vitro a partir de explantes de folha imatura excisados de plantas de duas variedades nacionais (RB739735 e RB72454) de cana-de-açúcar (Saccharum officinarum L.), mantidas em campo. Os explantes foram obtidos de plantas com 6-9 meses e cultivados em meio MS sólido suplementado com 2,4-D a 9 miM. As culturas foram mantidas no escuro, durante quatro semanas. A eficiência de formação de calos foi influenciada pelo genótipo. Os calos derivados da variedade RB72454 eram mucilaginosos e não originaram plantas. Explantes da variedade RB739735 formaram calos amarelos friáveis e embriogênicos (tipo II), que mantiveram sua capacidade proliferativa por, pelo menos, seis meses. Após transferência para meio MS sem reguladores de crescimento e em condições de iluminação, 56% desses calos originaram plantas, resultando na produção de, em média, 50 plantas por calo, após dois meses de cultura. As plantas continuaram a se desenvolver, originando novos brotos após transferência para meio MS0 líquido, não sendo observadas anormalidades fenotípicas. A inibição do desenvolvimento dos calos em resposta a diferentes concentrações de antibióticos usados em protocolos de transformação genética foi também avaliada. Foi observada inibição na presença de canamicina a 128,7 miM e de higromicina a 94,8 miM. Não foi obtido nenhum efeito inibidor do antibiótico geneticina (G418), em concentrações entre 43,3 e 86,6 miM.

Morfologia comparada de plântulas e plantas jovens de leguminosas arbóreas nativas: espécies de Phaseoleae, Sophoreae, Swartzieae e Tephrosieae

Dados morfológicos referentes às fases juvenis das plantas são tão importantes quanto escassos na literatura. Neste trabalho, foram estudadas as plântulas e plantas jovens de Erythrina speciosa (Phaseoleae), Holocalyx balansae e Sophora tomentosa (Sophoreae), Swartzia langsdorffii (Swartzieae), Lonchocarpus muehlbergianus e Platycyamus regnellii (Tephrosieae), como parte de um amplo projeto com leguminosas arbóreas, que objetivou descrever a morfologia das fases juvenis, com vistas à identificação das espécies, fornecendo subsídios para trabalhos taxonômicos, filogenéticos e ecológicos. Erythrina speciosa apresentou plântula epígeo-carnosa, formando somente dois eofilos. As espécies de Sophoreae e Swartzieae formaram plântulas hipógeas, sendo constituídos de cinco a sete eofilos em Holocalyx balansae, de seis a 15 em Sophora tomentosa e de sete a 10 em Swartzia langsdorffii. Em Tephrosieae, Lonchocarpus muehlbergianus produziu plântula hipógea e constituiu de oito a 10 eofilos e Platycyamus regnellii formou plântulas epígeo-carnosas e apenas dois eofilos. As plântulas e plantas jovens de Erythrina speciosa e de Platycyamus regnellii são similares, sendo distinguidas somente pela presença de espinhos e nectários extra-florais na primeira. Com relação à filotaxia, as espécies de Sophoreae e Swartzieae apresentaram somente nós alternos, enquanto que, em Phaseoleae e Tephrosieae, a filotaxia do primeiro nó eofilar foi oposta, passando a alterna nos nós subsequentes. Foram encontrados nódulos radiculares em todas as espécies, exceto em Holocalyx balansae e em Platycyamus regnellii.

Ultrastructural analysis of in vitro direct and indirect organogenesis

This is a comparative study of the ultrastructural characteristics of the cells involved in the organogenesis in vitro of Bauhinia forficata Link (indirect system) and Glycine max (L.) Merrill (direct system). B. forficata calli after 30 days culture and G. max meristemoids after 10 days culture were prepared for ultrastructural analysis using conventional methods. Concentrically arranged rough endoplasmic reticulum (RER) and plastids containing starch grains were seen during G. max and B. forficata organogenesis. The amitotic process, the presence of plastids around the nucleus and nuclear envelope with conspicuous pores were found in B. forficata.

Juvenile dynamics of the endemic and rare Enterolobium glaziovii Benth. (Mimosaceae) around reproductive trees in the Atlantic forest, Brazil

Studies on the regeneration and seedling mortality of rare tree species are important, but scarce. The aim of this study was to investigate the annual variation in recruitment, growth and mortality of juveniles of Enterolobium glaziovii Benth., a rare tree species from the Brazilian Atlantic Rain Forest. All seedlings and juveniles around four reproductive trees were labeled and their fate was followed from 1996 to 1999. There were no annual differences in juveniles' recruitment below and beyond the parental crown, but juveniles' survival and growth were lower below than beyond of the parental tree crowns. Small individuals (< 15 cm tall) showed the greatest mortality and the lowest growth, followed by medium (from 15 to 50 cm tall) and large ones (> 50 cm tall). Large juveniles were more widely dispersed from the conspecific parental tree than were medium and small ones. This suggests that distance dependent mortality of juveniles mediated by the parental tree is an important cause of spacing shifts associated with the growth of small individuals of E. glaziovii into large ones. Widely dispersed juveniles may escape the high mortality associated with pathogens, herbivores or seed predators concentrated around adult conspecifics. The negative influence of the parental tree on its juveniles may explain the sparse distribution of its adults in the forest.

Changes in plant community diversity and composition across an edge between Araucaria forest and pasture in South Brazil

This work investigated how richness, abundance, composition and structure of woody and herbaceous vegetation were altered by the proximity of an edge between Araucaria forest and pasture in South Brazil. Herbaceous and woody species including seedlings were surveyed in 42 plots of 5 × 5 m randomly placed at the following distances: 5 and 50 m from the edge into the pasture and 0, 25, 50, 100 and 250 m from the edge into the forest. There was a significant increase in vegetation cover, richness and abundance of woody species, woody seedlings and herbaceous plants at the edge (0 m). These variables, in general, decreased from 25 to 50 m from the edge into the forest in comparison to the forest interior. Few seedlings of woody plants were able to establish themselves in the pasture. There were continuous changes in species composition that occurred in the studied gradient due to the invasion of light-demanding species and the disappearance of some shade-tolerant species at the edge. In conclusion, the forest edge studied generated changes in the plant community that extended up to 50 m into the forest.

Population structure of Eschweilera coriacea (DC.) S. A. Mori in forest fragments in eastern Brazilian Amazonia

The population structure of a common canopy tree was examined in three sites to investigate the possible effects of forest fragmentation in eastern Amazonia. Evidence for the escape hypothesis of differential seed/seedling survival was evaluated. Two 1 ha plots were established at each site and all individuals of Eschweilera coriacea (DC.) S. A. Mori over 1 m tall were tagged, measured and mapped. Smaller individuals were recorded in the same way within subplots. Mature individuals were abundant at all sites with densities of 32-52 ha-1. The species exhibited substantial regeneration, although total population density varied fourfold among sites (1,256-4,805 individuals ha-1). Overall, juveniles were clumped while adults were randomly distributed. The difference between the dispersion pattern of adults and juveniles supported the escape hypothesis. However, no difference in population structure among sites could be related to the forest fragmentation.

The potential of natural regeneration of rocky outcrop vegetation on rupestrian field soils in "Serra do Cipó", Brazil

An area's innate potential to regenerate represents a crucial factor for its conservation and management. The seed rain and seed bank are important agents in the regeneration process. Seed banks are particularly important in communities where there is a high proportion of obligate seeders. Rocky outcrops are habitats where most part of the plant species depends on their seeds to reproduce and maintain viable populations. Therefore, seed banks ought to be important in this vegetation physiognomy. We test the hypotheses that the seed bank of the rocky outcrops found in the rupestrian fields of "Serra do Cipó", Brazil, is richer in species and denser than those formed on different vegetation physiognomies neighboring the outcrops. We then compared species abundance, species richness and composition in the rocky outcrops' seed banks with those of sandy and peaty bogs, forests, gallery forests, and "cerrados". Furthermore, we report on the natural regeneration potential of these soils by assessing a greenhouse study on seedling emergence. Soil samples were collected from 0 to 5 and 5 to 10 cm of depth. Rocky outcrops had the poorest in species and less dense seed bank and showed segregation in species composition. Emergence was greater in the most superficial layer. However, soils on rocky outcrops showed the greatest proportion of endemic threatened species in their seed banks, demonstrating their importance for biodiversity conservation of the "Serra do Cipó" rupestrian fields.

Anatomical and developmental aspects of leaf galls induced by Schizomyia macrocapillata Maia (Diptera: Cecidomyiidae) on Bauhinia brevipes Vogel (Fabaceae)

Samples of healthy leaves and galls induced by Schizomyia macrocapillata Maia on Bauhinia brevipes Vogel were submitted to routine techniques to investigate gall anatomy and development. Pouch galls are induced on the abaxial surface of unfolded immature leaves, and become spheroid with long reddish hairs covering their external surface. Galls occur isolated or coalesce when in larger numbers. Gall development was divided into six phases: 1) initiation; 2) tissue re-arrangement; 3) tissue differentiation; 4) maturation; 5) growth phase; and 6) dehiscence. This last phase corresponds to gall senescence, which takes place just after the larva exits the chamber to pupate. An important developmental phase of tissue reorientation was recorded after the initiation phase. The presence of hyphae close to the covering layer characterizes this gall as an ambrosia gall and the feeding mode of the gall migde is discussed. Few hyphae were found during the first developmental phases and fungi may play an important role during gall morphogenesis. Neoformed trichomes may provide not only photoprotection but also protection against natural enemies and water loss. The neoformation of phloematic bundles suggests host manipulation and indicates the establishment of a deviating sink.

Flowering and fruiting of Aulonemia aristulata: a gynomonoecious woody bamboo species from Atlantic Forest in Brazil

Aulonemia aristulata (Döll) McClure is a lignified bamboo species endemic to Brazil. This species occurs in southeastern forests and can reach high density at forest edges, dominating the understory of canopy-disturbed forest patches. The goal of this study was to describe the flowering period, floral biology, fruiting and seedling recruitment of A. aristulata in natural conditions in two areas located in a segment of the Atlantic Forest. Data on the morphology of the synflorescences and florets, timing and sequence of the anthesis events and floral visitors were recorded. Natural pollinators (open pollination or control) as well as spontaneous self-pollination were also checked. Pollen viability was estimated using the acetocarmine technique. Aulonemia aristulata is monocarpic (semelparous) with gregarious flowering. All culms in both studied areas blossomed and fruited between August and November 2007, dying subsequently between December 2007 and April 2008. Two types of synflorescences and flowers were observed: terminal with bisexual and protandric florets, with the anthesis lasting for 3-4 days; and axillary, with morphologically bisexual, but functionally female, florets and anthesis lasting for 3-4 days. The latter were also observed in the rhizome of plants whose aerial portion had been removed. The presence of axillary synflorescences with pistillate flowers is described here for the first time in Aulonemia species. Moreover, this is the first report of gynomonoecy in woody bamboo. Fruiting from bisexual florets under natural conditions (35%) was superior to that obtained from bagged synflorescences (11.5%). Fruiting from functional female florets was around 20%. Pollen viability was on the average of 90%. The results suggest that Aulonemia aristulata is anemophilous. The massive bamboo seedling recruitment observed after dieback with the ability to colonize open areas could promote the regeneration of Aulonemia aristulata.

Physiological, morphological and biochemical characteristics of the sexual propagation of Piper aduncum (Piperaceae)

In this work we attempted to characterize the diaspores and the germination process of Piper aduncum L., as well as to verify the influence of the interaction between presence and absence of light (photoperiod of 12 hours and dark) and temperature (25 °C, 30 °C and 20-30 °C) and also of gibberellin (0, 50, 100, 200 and 400 mg L-1) on the root protrusion and normal seedlings formation. The diaspores are very small with a thousand seed weight of 0.3645 g, 13% moisture and protein reserve. Diaspores are strict positively photoblastic in the tested temperature range and the optimum temperature for root protrusion was 30 °C, while for normal seedlings was 25 °C. The previous permanence in the dark led to an increase in the speed of root protrusion and percentage and speed of seedling formation. The application of gibberellic acid negatively interfered with the protrusion and growth of the radicle while favoring the elongation of hypocotyls.