Increasing the performance of Passion fruit (Passiflora edulis) seedlings by LED light regimes.

Due to progress in the industrial development of light-emitting diodes (LEDs), much work has been dedicated to understanding the reaction of plants to these light sources in recent years. In this study, the effect of different LED-based light regimes on growth and performance of passion fruit (Passiflora edulis) seedlings was investigated. Combinations of different light irradiances (50, 100, and 200 µmol m-2 s-1), quality (red, green, and blue light-emitting LEDs), and photoperiods (10 h/14 h, 12 h/12 h and 14 h/10 h light/dark cycles) were used to investigate the photosynthetic pigment contents, antioxidants and growth traits of passion fruit seedlings in comparison to the same treatment white fluorescent light. Light irradiance of 100 µmol m-2 s-1 of a 30% red/70% blue LED light combination and 12 h/12 h light/dark cycles showed the best results for plant height, stem diameter, number of leaves, internode distance, and fresh/dry shoot/root weights. 14 h/10 h light/dark cycles with the same LED light combination promoted antioxidant enzyme activities and the accumulation of phenols and flavonoids. In contrast, lower light irradiance (50 µmol m-2 s-1) had negative effects on most of the parameters. We conclude that passion fruit seedlings' optimal performance and biomass production requires long and high light irradiances with a high blue light portion.

Methods of aril removal and lightness conditions on seeds physiological quality of sour passion fruits / Métodos de remoção do arilo e condições de luminosidade sobre a qualidade fisiológica das sementes de maracujá azedo

Abstract Passion fruits species presents a larger economic importance for in natura consumption and industry. The main way to propagate these species is by seeds; however, the aril presence and environmental conditions may inhibit the seeds germination. In this sense, the objective of this study was to evaluate the effect of aril removal methods and light conditions on P. edulis var. flavicarpa seeds quality and germination. There were used five methods to remove the seeds aril: (1) friction on steel mesh sieve for 5 minutes; (2) friction with coarse sand on steel mesh sieve for 5 minutes; (3) immersion in lime solution at 10% (w/v), for 30 minutes; (4) fermentation in sugar solution at 10% (w/v), during 48 hours; and (5) natural pulp fermentation, during five days. The seeds were submitted to germination test at darkness and lightness, as well as, to length seedlings and emergence test. Regardless the aril removal method, the germination percentage was lower at lightness than darkness highlighting the natural pulp fermentation treatment, which presented 86% of seeds germinated. On the other hand, the aril removal methods did not affect the seedlings emergence, with emergence percentages ranged from 88 to 94%.

Resumo As espécies de maracujá apresentam grande importância econômica, tanto para o consumo in natura, quanto para a indústria. A principal maneira de propagar essas espécies é por sementes; contudo, a presença de arilo e condições ambientais pode inibir a germinação. Nesse sentido, objetivou-se estudar o efeito de métodos de remoção do arilo e luminosidade na qualidade e germinação das sementes de Passiflora edulis var. flavicarpa. Cinco métodos foram empregados para a remoção do arilo: (1) fricção em peneira de malha de aço por cinco minutos; (2) fricção com areia grossa em peneira de malha de aço por cinco minutos; (3) imersão em solução de cal a 10% (m/v), por 30 minutos; (4) fermentação da polpa em solução de açúcar a 10% (m/v), por 48 horas; e (5) fermentação natural da polpa, por cinco dias. As sementes foram submetidas ao teste de germinação no escuro e no claro, teste de comprimento de plântulas e teste de emergência. Independente do método de remoção do arilo, a porcentagem de germinação no claro apresentou-se menor em comparação ao escuro, com destaque para o tratamento de fermentação natural da polpa, o qual apresentou 86% de sementes germinadas. Por outro lado, os métodos de remoção do arilo não afetaram a emergência das plântulas, com porcentagem de emergência variando entre 88 a 94%.

Methods of aril removal and lightness conditions on seeds physiological quality of sour passion fruits.

Passion fruits species presents a larger economic importance for in natura consumption and industry. The main way to propagate these species is by seeds; however, the aril presence and environmental conditions may inhibit the seeds germination. In this sense, the objective of this study was to evaluate the effect of aril removal methods and light conditions on P. edulis var. flavicarpa seeds quality and germination. There were used five methods to remove the seeds aril: (1) friction on steel mesh sieve for 5 minutes; (2) friction with coarse sand on steel mesh sieve for 5 minutes; (3) immersion in lime solution at 10% (w/v), for 30 minutes; (4) fermentation in sugar solution at 10% (w/v), during 48 hours; and (5) natural pulp fermentation, during five days. The seeds were submitted to germination test at darkness and lightness, as well as, to length seedlings and emergence test. Regardless the aril removal method, the germination percentage was lower at lightness than darkness highlighting the natural pulp fermentation treatment, which presented 86% of seeds germinated. On the other hand, the aril removal methods did not affect the seedlings emergence, with emergence percentages ranged from 88 to 94%.

Effect of training system and climate conditions on phytochemicals of Passiflora setacea, a wild Passiflora from Brazilian savannah.

Passiflora setacea is a Brazilian savannah fruit known as a good source of phytochemicals. The phytochemical composition is influenced by environmental factors and management techniques such as training system. This study aimed to evaluate the influence of training system (espalier or trellis) and environmental factors (temperature, precipitation and sunlight exposure) on antioxidant capacity and bioactive composition of P. setacea pulp. Total phenolic compounds (TP), proantocyanidins (PA), total flavonoids (TF), vitamin C and total antioxidant activity were analyzed. Five flavonoids (orientin, isoorientin, vitexin, isovitexin and hesperetin) were determined by HPLC-DAD, using calibration curves. Training system presented no effects on TP, PA, TF and antioxidant activity, whereas rainy season year 2 increased FRAP values, TF, orientin, isovitexin and hesperetin content, which could be associate to climate stressful condition leading to higher levels of these compounds.

No time for candy: passionfruit (Passiflora edulis) plants down-regulate damage-induced extra floral nectar production in response to light signals of competition.

Plant fitness is often defined by the combined effects of herbivory and competition, and plants must strike a delicate balance between their ability to capture limiting resources and defend against herbivore attack. Many plants use indirect defenses, such as volatile compounds and extra floral nectaries (EFN), to attract canopy arthropods that are natural enemies of herbivorous organisms. While recent evidence suggests that upon perception of low red to far-red (R:FR) ratios, which signal the proximity of competitors, plants down-regulate resource allocation to direct chemical defenses, it is unknown if a similar phytochrome-mediated response occurs for indirect defenses. We evaluated the interactive effects of R:FR ratio and simulated herbivory on nectar production by EFNs of passion fruit (Passiflora edulis f. flavicarpa). The activity of petiolar EFNs dramatically increased in response to simulated herbivory and hormonal treatment with methyl jasmonate (MeJA). Low R:FR ratios, which induced a classic "shade-avoidance" repertoire of increased stem elongation in P. edulis, strongly suppressed the EFN response triggered by simulated herbivory or MeJA application. Strikingly, the EFN response to wounding and light quality was localized to the branches that received the treatments. In vines like P. edulis, a local response would allow the plants to precisely adjust their light harvesting and defense phenotypes to the local conditions encountered by individual branches when foraging for resources in patchy canopies. Consistent with the emerging paradigm that phytochrome regulation of jasmonate signaling is a central modulator of adaptive phenotypic plasticity, our results demonstrate that light quality is a strong regulator of indirect defenses.

Induction of flavonoid production by UV-B radiation in Passiflora quadrangularis callus cultures.

Callus cultures from several species of Passiflora were initiated in vitro, and their capacity to produce four glycosyl flavonoids (orientin, isoorientin, vitexin, isovitexin) was analysed. The aim of the present work was to examine the possible role of UV-B irradiation and elicitation with methyl jasmonate (MJ) on the production of these compounds in callus cultures. All the species tested (P. incarnata, P. quadrangularis, P. edulis) formed friable callus from leaf explants after 4 weeks on medium supplemented with kinetin and 2,4-dichlorophenoxyacetic acid. Among them, P. quadrangularis turned out to have a faster growth rate and a more friable texture, and was therefore chosen for experiments with elicitors. In callus cultures only small amounts of isoorientin were found, while the concentration of the other flavonoids was below the detection limit. UV-B irradiation of calluses was able to increase the production of all four glycosyl flavonoids. After a 7-day exposure of cultures to UV-B light, the production of isoorientin reached concentrations similar to those found in fresh leaves from glasshouse-grown plants. Elicitation with methyl jasmonate also enhanced orientin, vitexin and isovitexin concentrations, even though the stimulation was about 6-fold weaker for orientin and vitexin and about 40-fold for isovitexin, than that exerted by UV-B treatment. Callus cultures treated with the UV-B dose which most enhanced flavonoid production showed a higher antioxidant activity compared to untreated calluses, with an increase ranging from 28% to 76%. Results show that the secondary metabolite biosynthetic capacity of Passiflora tissue cultures can be enhanced by appropriate forms of elicitation.