Antelmo Ralph Falqueto

Atividade da pectinametilesterase e sua relação com a perda de firmeza da polpa de mamão cv. Sunrise Solo e Tainung

The objective of this work was to evaluate the pectinmethylesterase (PME) activity in papaya (Carica papaya L.) fruits cv. Sunrise Solo and Tainung, and to correlate its changes with the pulp firmness loss during fruit ripening. Fruits were collected daily from a commercial farm localized in Aracruz - ES, and stored under room temperature (approximately 25 °C) until the period of analysis. The pulp firmness loss of the fruits in both cultivars began at the 4th day after harvest (DAH); however, the cv. Sunrise Solo presented highest reduction than the cv. Tainung. The PME activity of cv. Sunrise Solo was higher at the 1st DAH, and decreased slowly at the 4th DAH, reaching its smallest value. At the 5th DAH the activity increased, remaining practically the same at the 8th DAH. In the cv. Tainung, the PME activity increased until the 3rd DAH and decreased at the 4th DAH. In the 5th DAH, its activity increased again reaching its higher value at the 6th DAH. From this on, the enzyme activity decreased significantly, maintaining the same value until the last day of analysis (8th DAH). The correlation coefficient obtained between the PME activity and the pulp firmness in the cv. Sunrise Solo after the 4th DAH was R = - 0,84, indicating that during this period, the pulp firmness of the fruits decreased when the PME activity increased. On the other hand, there was no significant correlation between these two characteristics in the cv. Tainung.

Nitrate reductase activity and chlorophyll a fluorescence in papaya

The objective of the present work was to connect the nitrate reductase activity and the photochemical efficiency of the photosystem II (PSII), measured as FV/FM, in papaya (Carica papaya L.) cv. Tainung 01 and Sunrise Solo 72/12 in field conditions. The photochemical potential of PSII was measured in situ on attached leaves that had been dark adapted, prior to the fluorescence measurement. After, in same leaves, the enzyme activity was measured. There was not significant difference among the photochemical efficiency of PSII between cv. Tainung 01 and Sunrise Solo 72/12, even so, the activity of the enzyme was markedly higher in cv. Tainung 01 than in cv. Sunrise Solo 72/12. The nitrate redutase activity was highly correlated with the photochemical efficiency of the PSII in both cv. Tainung 01 (coefficient of correlation r= 0,740 and coefficient of determination r2= 0,706) and Sunrise Solo 72/12 (coefficient of correlation r= 0,960 and coefficient of determination r2= 0,945). These results suggest that there is a correlation between chlorophyll a fluorescence and nitrate reductase activity in these plants.

Photosynthetic performance of mangroves Rhizophora mangle and Laguncularia racemosa under field conditions

In mature mangrove plants Rhizophora mangle L. and Laguncularia racemosa Gaerth. growing under field conditions, photosystem 2 (PS2) photochemical efficiency, determined by the ratio of variable to maximum fluorescence (F v /F m ), increased during the day in response to salinity in the rainy seasons. During the dry season, fluorescence values ( Fo) were higher than those observed in rainy season. In addition, Fo decreased during the day in both season and species, except for R. mangle during the dry season. A positive correlation among F v /F m and salinity values was obtained for R. mangle and L. Racemosa during the dry and rainy seasons, showing that photosynthetic performance is maintained in both species under high salinities. Carotenoid content was higher in L. Racemosa in both seasons, which represents an additional mechanism against damage to the photosynthetic machinery. The chlorophyll content was not affected by salinity in either species.

Características fotossintéticas de batata cv. Baronesa e seu genótipo transformado geneticamente para resistência ao PVY

Potato breeding is difficult and requires a great deal of time and energy. The use of recombinant DNA technology, with its potential capacity of isolating and transferring genes from any organism, allows incorporating in plants new characters of agricultural interest. However, consequences of the incorporation of determined genes on physiological characteristics are sometimes unknown. In this study we evaluated photosynthetic characteristics of potato plants genetically modified with resistance genes to PVY. Potato tubers of cv. Baronesa and its respective transformed genotype were planted in pots and kept in greenhouse. During the plant life cycle, parameters of chlorophyll fluorescence, net photosynthesis and potential photosynthesis were evaluated. Plants transformed with PVY resistant genes showed higher maximum photochemical efficiency and higher oxygen evolution rate, however the parameters of chlorophyll fluorescence and net photosynthesis were the same.

Effects of 6-benzylaminopurine on photosystem II functionality and leaf anatomy of in vitro cultivated Aechmea blanchetiana

Cytokinins (CKs) are often used during the in vitro cultivation of plant species. However, it is not clear how CKs, such as 6-benzylaminopurine (BAP), affect photosystem PS) II functionality and leaf anatomy over a long period of in vitro plant propagation. The aim of this study was to analyze the residual effects of BAP on the photosynthetic performance and leaf anatomy of Aechmea blanchetiana after 120 d without exposure to CKs. Aechmea blanchetiana plants previously grown in vitro were transferred to Murashige and Skoog (MS) culture media containing 0, 5, 10, 15, or 20 μM BAP. After 60 d on the MS medium with BAP, explants were subcultivated twice on the MS medium without growth regulators, first in a stationary liquid medium for 60 d and then in a solidified medium with 6 g dm-3 agar for 60 d. Leaf anatomy, pigment content, and chlorophyll a fluorescence were assessed for plants from each treatment after 120 d on the CK-free medium. Stomatal density presented a negative linear correlation with BAP concentration. Pigment content decreased in plants subjected to previous BAP exposure. An increase in absorbed energy flux per reaction center (ABS/RC) and a sharp decrease in energy transport flux (ETo/RC) followed by an increase in energy dissipation flux (DIo/RC) also occurred. Furthermore, maximum quantum yield (FV/FM) decreased as a function of BAP concentration. Thus, the use of BAP during in vitro propagation of A. blanchetiana induced long-term physiological defects.

Anatomy and photosystem II activity of in vitro grown Aechmea blanchetiana as affected by 1-naphthaleneacetic acid

Auxins are one of the main regulators of in vitro plant growth and development. However, the mechanisms, by which auxins, such as 1-naphthaleneacetic acid (NAA), affect in vitro root and leaf anatomy and photosystem function, remain unclear. Accordingly, the aim of the present study was to analyze the effect of different NAA concentrations on the anatomy and photosynthetic performance of in vitro-propagated Aechmea blanchetiana and to determine whether such a treatment affects micropropagated plants after acclimatization. In vitro-established A. blanchetiana plants were transferred to culture media that contained 0, 2, 4, or 6 μM NAA, and after 50 d, they were transplanted into plastic seedling trays with a commercial substrate and cultivated for 60 d in a greenhouse. The plants were evaluated after a 50-d in vitro NAA exposure (growth traits, chlorophyll α fluorescence, and root and leaf anatomy) and after 60 d of acclimatization in the greenhouse (root and leaf growth). Changes induced by NAA in root anatomy might improve uptake of minerals and sugars from the medium, thereby increasing the in vitro growth. In the leaves, the lowest chlorenchyma thickness and sclerenchyma area were observed in plants grown without NAA, and NAA exposure also improved photosystem II activity. The highest ex vitro growth rate was observed for plants that were propagated with 4 μM NAA. Therefore, the use of NAA during in vitro propagation can improve the anatomical and physiological quality of A. blanchetiana plants, as well as to improve ex vitro transfer.

Fluorescência transiente da clorofila a e crescimento vegetativo em cafeeiro conilon sob diferentes fontes nitrogenadas

The use of nitrogen fertilizers is an effective resource to increase the coffee yield, so that the improvement and /or generation of new techniques that assist in the management of nitrogen fertilization are essential, as will contribute to increase nitrogen use efficiency (N). Thus, this study aimed to determine the chlorophyll a fluorescence transient and vegetative growth in Conilon coffee under different nitrogen sources. The experiment was carried out in Nova Venécia ES Brazil, on coffee plantation Conilon cultivar “Vitória Incaper 8142”. Were evaluated five sources of nitrogen fertilizers: urea common, urea + NBPT, urea + Cu and B, urea + S, and ammonia nitrate. The chlorophyll a fluorescence maximum did not differ in any of the times examined. The values of relative chlorophyll index (RCI) alternated their significance with respect to treatments throughout the evaluation dates. The N sources were not responsible, singly, with changes to the RCI. The sources of nitrogen fertilizers with increased efficiency exhibited low influence on transient fluorescence of chlorophyll a and do not influence the vegetative growth of the coffee.