Latex dilution reaction during the tapping flow course of Hevea brasiliensis and the effect of Ethrel stimulation

The latex dilution reaction during the tapping flow course has been well documented and associated with the facilitation of tapping latex flow. However, its underlying mechanism has not experimentally examined. The latex total solid content, osmotic potential and phloem turgor pressure change during the tapping flow course were simultaneously measured to investigate the cause of water movement during the tapping flow course. It was found that there are three different stages for the laticifer water equilibrium during the tapping flow course. The tapping-induced rapid turgor pressure drop is the cause of the first stage water influx into laticifers, while osmoregulation prevails during water exchange in the second and third stages of tapping flow. Meanwhile, aquaporin expressions were, for the first time, investigated during the tapping flow course. The rapid transcript up-regulation of HbPIP1, HbPIP2;1 and HbPIP2;3 contributes to the latex dilution reaction. However, their activity gating cannot be ruled out. Ethrel stimulation can significantly dilute the corresponding latex fractions during the tapping flow course due to its up-regulations of HbPIP1, HbPIP2;1 and HbPIP2;3. Nevertheless, the latex dilution reaction pattern for the Ethrel treated trees did not change, except for a lower degree of dilution compared with the un-treated trees. All these results suggest that both phloem turgor pressure and aquaporins are involved in the latex dilution reaction during the tapping flow course.

Hormones andCuscuta development: In vitro induction of haustoria by cytokinin and its inhibition by other hormones

Cytokinins induced haustoria formation in excised 10-mm segments ofCuscuta vine, the subapical 25-to-50-mm region being most responsive, producing a mean of 4–6 haustoria per segment. The order of effectiveness of cytokinins continuously applied (72 h) was 6-benzylaminopurine (BA) ges isopentenyladenine (iP) Gt zeatin (Z). Ribosides of BA and Z were as effective as the bases, whereas riboside of iP ([9R]iP) was half as effective as iP. Haustoria induction was influenced by weather and seasonal conditions at the time of vine collection; materials obtained on warm, sunny days responded better than those obtained on rainy, cloudy, or cool days. Haustoria were induced equally well all around the segment, and no thigmostimulus was needed for induction. p ]A 10-min pulse of 100 mgrM BA induced half as many haustoria as a 60-min pulse or continuous application of BA. White light inhibited haustoria induction elicited by a short (30-min) pulse of BA, whereas a longer (120-min) BA application overcame this light inhibition. Auxins (IAA or NAA, 1–10 mgrM), gibberellin (GA3, 1–10 mgrM), ethylene (as ethrel, 10–100 mgrM), and abscisic acid (ABA, 100 mgrM) were individually inhibitory (60–80%) with respect to haustoria induction when given continuously with 50 mgrM BA. A 60-min pulse of auxins (10 mgrM), GA3 (100 mgrM), or ethrel (10 mgrM), given at various time intervals during or after a 60-min pulse of 100 mgrM BA, showed that inhibition was maximal (70–95%) between 4 and 16 h of BA application and negligible (GA3) or much reduced (auxin, ethrel) at 20 h, indicating a ldquocommitmentrdquo to haustoria formation by this time.

Rubber latex yield and physiology of rubber tree with tea tree oil treatments

To examine the effects of tea tree oil on rubber latex yield and the resulting latex physiological parameters of rubber tree （Hevea brasiliensis），clean water and 20%，40%，60%，80% and 100% of tea tree oil were applied on the tapping cut of rubber trees. The data were analyzed by Duncan test and its results showed that when compared to clean water （ck），80% and 100% of tea tree oil stimulation significantly promoted rubber latex yield（P＜0.05）. In addition，the latex physiological parameters changed with the sucrose content（P＜0.01），magnesium ion content （P＜0.01） and inorganic phosphorus content （P＜0.01） of latex significantly increasing and thiol content significantly deceasing （P＜0.01）. The effect of tea tree oil treatments on rubber yield was similar to the impact of 0.5% ethrel stimulation. However，compared to ethrel stimulation，100% tea tree oil treatment significantly increased dry rubber and sucrose contents （P＜0.01） and decreased thiol content （P＜0.01）. Thus，tea tree oil treatment involved different latex yield promotion mechanisms than that of ethrel stimulation.

Variation of phloem turgor pressure in Hevea brasiliensis: An implication for latex yield and tapping system optimization

Phloem turgor pressure (PTP) is the initial driving force for latex flow after a rubber tree is tapped and therefore plays an important role in rubber tree latex production. Variation in PTP with rubber tree clone, age, yield potential and commonly used Ethrel (an ethylene releaser) stimulation have, however, not been comprehensively studied to date. The aim of this study was to investigate these relations and examine whether PTP can be used as an index for rubber tree clone assessment and tapping system optimization. The results showed that: (1) the daily change of PTP in the foliation season suggests that a high PTP can ensure a high latex yield and tapping could be moved forward to midnight or earlier in the night; (2) the decrease of PTP from the basal to distal stem indicates the benefit of a controlled upward tapping system; (3) the logarithmic increase in PTP with rubber tree planting age and age-based mean girth suggests that the preferred age for the commencement of rubber tree tapping is eight years; (4) the change of PTP with regenerated bark age suggests that the regenerated bark could be exploited again after the second year; (5) PTP is positively related to the yield potential of rubber tree clones; (6) although Ethrel stimulation could not significantly increase the initial PTP of a rubber tree, it delays the recovery of PTP after tapping. Therefore, PTP is an indicator of rubber tree latex yield and can be used for tapping system optimization. © 2014 Elsevier B.V.

Regulation of HbPIP2;3, a latex-abundant water transporter, is associated with latex dilution and yield in the rubber tree (Hevea brasiliensis Muell. Arg.)

Rubber tree (Hevea brasiliensis) latex, the source of natural rubber, is synthesised in the cytoplasm of laticifers. Efficient water inflow into laticifers is crucial for latex flow and production since it is the determinant of the total solid content of latex and its fluidity after tapping. As the mature laticifer vessel rings are devoid of plasmodesmata, water exchange between laticifers and surrounding cells is believed to be governed by plasma membrane intrinsic proteins (PIPs). To identify the most important PIP aquaporin in the water balance of laticifers, the transcriptional profiles of ten-latex-expressed PIPs were analysed. One of the most abundant transcripts, designated HbPIP2;3, was characterised in this study. When tested in Xenopus laevis oocytes HbPIP2;3 showed a high efficiency in increasing plasmalemma water conductance. Expression analysis indicated that the HbPIP2;3 gene was preferentially expressed in latex, and the transcripts were up-regulated by both wounding and exogenously applied Ethrel (a commonly-used ethylene releaser). Although regular tapping up-regulated the expression of HbPIP2;3 during the first few tappings of the virginal rubber trees, the transcriptional kinetics of HbPIP2;3 to Ethrel stimulation in the regularly tapped tree exhibited a similar pattern to that of the previously reported HbPIP2;1 in the virginal rubber trees. Furthermore, the mRNA level of HbPIP2;3 was associated with clonal yield potential and the Ethrel stimulation response. Together, these results have revealed the central regulatory role of HbPIP2;3 in laticifer water balance and ethylene stimulation of latex production in Hevea.

Degreening of 'Satsuma Okitsu' Tangerine

Fruit of 'Satsuma Okitsu' tangerine are similar to 'Ponkan', with a maturation period starting in January, and supplying the Brazilian market during the off-season. Fruits of this cultivar have to be harvested with green peel, which is not well accepted by the market. This study aimed to evaluate the degreening of 'Satsuma Okitsu' tangerine using ethephon (2-chloroethyl phosphonic acid). The fruits were harvested with stems when they reached soluble solids: acidity ratio of >7. After selection, the fruits were treated with the Imazalil fungicide (200 ml 100 L-1) for two min and after 24 hours fruits were dipped in different concentrations of ethephon (Ethrel 240): control, 250, 500 and 1000 ppm. The fruits were analyzed every 3 days during 9 days of storage at 18 +/- 2 degrees C, 85 +/- 5% RH for appearance, weight loss, rind color, soluble solids, acidity and ascorbic acid content. The experiment was conducted as a factorial in a completely randomized design. The treatment with Ethrel provided the best flavedo or rind degreening which made these fruits turn orange with greater intensity and showed good quality during 9 days at 18 degrees C, besides increase in weight loss.

Reguladores vegetais e atividade de invertases em cana-de-açúcar em meio de safra

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Superação de dormência de sementes e crescimento inicial de plântulas de umbuzeiro

Pre-germination treatments such as scarification and the use of growth regulators can provide the overcoming of dormancy in seeds and enhance the emergence and development of seedlings. The aim of this study was to determine appropriate treatments to overcoming seed dormancy and enhance the initial growth of seedlings of Spondias tuberosa. We used a randomized design in factorial 2 x 4, with the following factors: seeds scarified or not scarified and then soaked in water or aqueous solutions of gibberellin, cytokinin and ethylene, with 4 replicates and 15 seeds. There was no significant interaction between scarification treatments and use of growth regulators. Mechanical scarification and soaking of seed of umbuzeiro in solutions containing growth regulators does not increase the percentage of seedling emergence, however soaking in a solution of Ethrel at 100 ppm provides higher speed of emergence and root development.

Efeito da aplicação de etileno no pH, acidez, índice refratométrico e açúcares totais de frutos de manga, colhidos em estágio pré-climatérico

Este trabalho teve como objetivo o estudo da ação do etileno no amadurecimento de frutos de manga, tentando contribuir para o conhecimento da fisiologia do amadurecimento destes frutos. Foram utilizadas mangas (Mangifera indica L.), variedade Keitt, colhidas em estágio pré-climatérico. Estes frutos receberam tratamento com ethrel (500 e 1.000 ppm, com exceção da testemunha) e foram submetidos às seguintes determinações: pH, acidez, índice refratométrico e açúcares totais. A análise e interpretação dos resultados mostrou a inexistência de diferença estatística entre esses 3 tratamentos, indicando que a aplicação de ethrel não trouxe nenhuma vantagem na melhoria de qualidade dos frutos.

Influência do etileno sobre características químicas de frutos de manga var. Keitt, colhidos em estádio pré-climatérico

Frutos de manga (Mangifera indica L.) variedade Keitt, colhidos em estádio pré-climatérico, receberam tratamento com 500 e 1.000 ppm de Ethrel (com exceção da testemunha), sendo submetidos a determinações de carboidratos solúveis, vitamina C, proteínas e umidade, de acordo com amostragens realizadas 3, 6, 9 e 16 dias pós-colheita. Os resultados obtidos, revelaram que o Ethrel não excerceu nenhuma influência nas características químicas dos frutos e que, somente em termos de carboidratos solúveis e vitamina C, os frutos mostraram alterações durante a maturação.

EFFECT OF TREATMENT WITH GROWTH-REGULATORS AND SCARIFICATION ON THE TOLERANCE TO WATER-STRESS IN SEEDS OF ORYZA-SATIVA LCVIAC-165

The effect of treatment of seeds of Oryza sativa L. cv. IAC 165 with gibberellic acid, 6-benzyladenine and ethrel on the tolerance to the water stress were analysed. Gibberellic acid had no effect and 6-benzyladenine and ethrel promoted slight increase in the tolerance to water stress, specially in darkness. After scarification, those growth regulator presented no effect. Our results suggest that 6-benzyladenine and ethrel promoted water stress tolerance due to the decrease in the resistance of the seed coat to embryo expansion.

Effect of growth regulators in citral content in lemongrass in different seasons (in Portuguese)

The purpose of the present research was to evaluate the effect of plant growth regulators in yield citral content in lemongrass (Cymbopogon citratus (D.C.) Stapf), in different seasons. The field experiment was conducted on Sao Manuel Experimental Farm, Agronomical Science College, Paulista Estatal University, Botucatu, Brazil, which soil was classified in alic yellon red latosol (Haplorthox). Plants were randommly assigned blocks to treatments with three repetitions. The experimental groups consisted of GA3 (50 and 100 mg.l-1);Ethrel (100 and 200 mgl-1); CCC (500 and 1000 mg.l-1); Alar 85 (1000 and 2000 mg.l-1); Accel (20 and 40 mg.l-1) and control group. Five applications of plant growth regulators were realized every other three months. After 40 days of each foliar spray, the plants were cut and determined the citral yield. The essential oils were extracted from leaf tissue by hydrodistillation in a Clevenger apparatus. Samples of 250g of leaf and put in Clevenger apparatus with deionized water for 3h to determine the yield of essential oil. The citral content was analyzed by GC. In the present study the concentrations of plant growth regulators used did not increase citral content.

Reguladores vegetais na produção de biomassa e teor de óleos essenciais em Cymbopogon citratus (DC.) Stapf, em diferentes épocas do ano

The purpose of the present research was to evaluate the effect of plant growth regulators in biomass production and essential oil yield content in lemongrass (Cymbopogon citratus (DC.) Stapf), in different seasons. The experiment was conducted on São Manuel Experimental Farm, Faculdade de Ciências Agronômicas, UNESP - Botucatu. Which plants were randomly assigned into blocks to treatments with three repetitions. The treatments consisted of GA3 (50 and 100 mg L-1); Ethrel (100 and 200 mg L-1); CCC (500 and 1000 mg L-1); Alar 85 (1000 and 2000 mg L-1); Accel (20 and 40 mg 0L-1) and control. Four applications of plant growth regulators were realized every three months. After 40 days of each foliar spray, the plants were cut to determine the fresh weight and essential oil yield. The application of plant growth regulators did not increase the biomass production, showing difference among collect periods when the major production was detected at the fourth collect (summer). The greatest essential oil yield was found at the second collect (winter). In the present study, the used concentrations of plant growth regulators did not increase biomass neither essential oil yield.

Maturação induzida, alterações fisiológicas, produtividade e qualidade tecnológica da cana-de-açúcar (Saccharum officinarum L.)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)