Application Of 6-benzylaminopurine Research Articles

Response of African Eggplant (Solanum macrocarpon L.) to Foliar Application of 6-Benzylaminopurine and Gibberellic Acid

Abstract The influence of foliar application of benzylaminopurine (BAP) and gibberellic acid (GA3) alone and in combination on quantitative and qualitative yields of Solanum macrocarpon L. ‘Igbagba’ was investigated to increase the production of the vegetable. Treatments were arranged in randomized complete block design with three replicates. Analysis of variance showed that treatments had significant (p < 0.05) influence on all parameters measured. Foliar application of 20–40 mg·dm−3 of GA3 alone doubled the shoot heights compared with other treatments. The highest leaf area, fresh shoot weight, dry weight and number of regrowth was observed on plants to which foliar application of 40 mg·dm−3 of BAP and 30 mg·dm−3 of GA3 was applied. Combinations of 40 mg·dm−3 of BAP and 30–40 mg·dm−3 of GA3 produced the highest quantities of chlorophyll a and chlorophyll b, carotenoids, total phenolics, soluble sugars and soluble protein. Highest moisture, crude protein, crude fat and ash contents were detected when 40 mg·dm−3 of BAP and 10–40 mg·dm−3 of GA3 were applied. However, the application of GA3 alone promoted crude fiber and carbohydrate synthesis. Leaf Na, P, Ca, Mg, Zn and Fe had highest quantities when 40 mg·dm−3 of BAP was combined with 30–40 mg·dm−3 of GA3. Leaf K was promoted by the application of BAP alone and combination of 40 mg·dm−3 of BAP and 10–20 mg·dm−3 of GA3. The highest number of re-growth was observed when 40 mg·dm−3 of BAP was combined with 30 mg·dm−3 of GA3. Foliar application of 40 mg·dm−3 of BAP and 30 mg·dm−3 of GA3 in combination was suggested for the enhancement of quantitative and qualitative yields of the vegetable.

CONCENTRAÇÕES DE AIB (ácido indolbutírico) E BAP (6-benzilaminopurina) NA ESTAQUIA DE JAMBOLEIRO(Syzygium cumini(L.) Skeels)

The aim of the study was to test different concentrations of indole-3-butyric acid and Benzylaminopurine in the jambolanpropagation by cuttings. The woody cuttings were obtained from plants approximately 15 years old and standardized with 12 cm in length, approximately 1.0 cm in diameter and two superficial lesions at the basal part, on opposite sides, with a portion of thebark being removed with about 0.5 cm wide by 2.5 cm in length, with apex cut in diagonal. The experimental design was completely randomized with factorial arrangement 3 × 3 *Indole-3-butyric acid (IBA) × Benzylaminopurine (BAP)+, with 4 replications, considering the use of 20 cuttingsper plot. The IBAconcentrations used were 0, 5000 and 10.000mg L-1and BAP 0, 250 and 500 mg L-1. The applications of the solutions were by immersion of 10 seconds in the base of the cuttings and conditioned in sand bed. After 120 days the characteristics of rooting and cuttings with calluses, number and length of primary shoots, number and length of roots were analyzed. The rooting percentage presented the highest result using 5,000 mg L-1of indole-3-butyric acid. However,the use of 10.000mg L-1of IBA provided a lower percentage of rooting, besides a higher number of dead cuttings. The use of Benzylaminopurine was not satisfactory for the rooting of jambolancuttings, since it did not provide increase in the rooting, thenumber of roots and the average size of the roots. The use of up to 5000 mg L-1of IBA without application of BAP was the most suitable for propagation of jambolanby cutting.

New insight into how thigmomorphogenesis affects Epipremnum aureum plant development

ABSTRACT Climbing Epipremnum aureum plants develop larger leaves than unsupported, hanging plants. This effect may be regarded, in part, as a thigmomorphogenic response, but gravimorphogenetic effect may also be involved, since polar auxin transport is known to be negatively affected in plants with horizontal or hanging stems, which may result in an altered hormone balance at the whole plant level. The present work was aimed at studying how exogenous auxins and cytokinins may influence growth of E. aureum rooted cuttings under different training systems. Rooted cuttings of E. aureum were cultivated either climbing on an upright wooden board or creeping on the glasshouse bench or hanging from a basket. All leaves of each plant were sprayed to run-off at sunset with four indole-3-acetic acid (IAA) doses 7 days after transplanting and one week later, with four benzylaminopurine (BAP) concentrations, rendering 16 hormone combination treatments. The application of IAA or BAP at 50 mg L-1 to creeping and hanging plants significantly promoted growth but, in climbing plants, a negative effect was generally observed. Changes in net assimilation and photosynthetic rates, together with modified allometric coefficients, accounted for these responses. The higher growth promotion by exogenous growth regulators observed in creeping or hanging plants compared to climbing plants, may be interpreted mostly as a gravimorphogenetic response.

Drought affects size, nutritional quality, antioxidant activities and phenolic acids of Moringa oleifera LAM.

To observe variation in growth performance, antioxidant activities, and nutritional quality of Moringa oleifera, we exogenously applied benzyl amino purine (BAP), ascorbic acid, and moringa leaf extract (MLE) to moringa plants at three field capacity levels, 100, 75, and 40% in a completely randomized design with three replications. We observed a decrease in growth, chlorophyll a and b, total phenolic contents, antioxidant activities, crude protein, and mineral contents of moringa leaves at 100 and 40% field capacity in comparison with 75% field capacity. BAP best improved growth performance of moringa plants, improving shoot length, root length, number of leaves and photosynthetic pigments, followed by MLE at 75% field capacity, while moringa plants showed reduced growth at 40% field capacity which was increased by BAP and MLE foliar application. Maximum contents of gallic acid, p-coumaric acid and sinapic acid were found in moringa leaves when the plants were sprayed with ascorbic acid while p-hydroxybenzoic acid and caffeic acid were maximally increased under 75% field capacity when the plants were subjected to BAP followed by MLE. The lowest and highest crude protein, calcium, potassium, magnesium, and phosphorous contents were recorded under 40 and 75% field capacity, with MLE impro-ving these contents under both conditions. It can safely be concluded that moringa plants showed retarded growth under 100 and 40% field capacity, and that the effects of deficit in nutritional quality were mitigated by applying BAP and MLE. Among these two plant growth regulators, MLE can be preferred being a natural source.

Effect of paclobutrazol and benzyl aminopurine application at two growth stages on yield and breaking dormancy of potato minitubers

Effect of paclobutrazol and benzyl aminopurine application at two growth stages on yield and breaking dormancy of potato minitubers

6-Benzylaminopurine treatment maintains the quality of Chinese chive (Allium tuberosum Rottler ex Spreng.) by enhancing antioxidant enzyme activity

Chinese chive usually develops an off-flavor after a short storage time. To explore effective ways to maintain the postharvest quality of Chinese chive, the effect of exogenous application of 6-benzylaminopurine (6-BA) on postharvest quality and antioxidant activity of chive was evaluated, and the mechanism of the physiological responses of chive to 6-BA treatment was explored. Chives were sprayed for 10 min with 100, 300, or 500 mg L−1 6-BA or with alkaline solution as the control, then stored at (2±1)°C with a relative humidity (RH) of 80–85%. We found that 300 mg L−1 6-BA significantly delayed yellowing and chlorophyll degradation, maintained the total phenolic and flavonoid content, and improved the activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). In conclusion, we identified exogenous application of 6-BA as an effective method for maintaining postharvest quality of Chinese chive. In addition, our finding that the activities of antioxidant enzymes increase in response to exogenous 6-BA provides new insights into the mechanism of cytokinin-based postharvest fresh-keeping.

Heat-Induced Cytokinin Transportation and Degradation Are Associated with Reduced Panicle Cytokinin Expression and Fewer Spikelets per Panicle in Rice.

Cytokinins (CTKs) regulate panicle size and mediate heat tolerance in crops. To investigate the effect of high temperature on panicle CTK expression and the role of such expression in panicle differentiation in rice, four rice varieties (Nagina22, N22; Huanghuazhan, HHZ; Liangyoupeijiu, LYPJ; and Shanyou63, SY63) were grown under normal conditions and subjected to three high temperature treatments and one control treatment in temperature-controlled greenhouses for 15 days during the early reproductive stage. The high temperature treatments significantly reduced panicle CTK abundance in heat-susceptible LYPJ, HHZ, and N22 varieties, which showed fewer spikelets per panicle in comparison with control plants. Exogenous 6-benzylaminopurine application mitigated the effect of heat injury on the number of spikelets per panicle. The high temperature treatments significantly decreased the xylem sap flow rate and CTK transportation rate, but enhanced cytokinin oxidase/dehydrogenase (CKX) activity in heat-susceptible varieties. In comparison with the heat-susceptible varieties, heat-tolerant variety SY63 showed less reduction in panicle CTK abundance, an enhanced xylem sap flow rate, an improved CTK transport rate, and stable CKX activity under the high temperature treatments. Enzymes involved in CTK synthesis (isopentenyltransferase, LONELY GUY, and cytochrome P450 monooxygenase) were inhibited by the high temperature treatments. Heat-induced changes in CTK transportation from root to shoot through xylem sap flow and panicle CTK degradation via CKX were closely associated with the effects of heat on panicle CTK abundance and panicle size. Heat-tolerant variety SY63 showed stable panicle size under the high temperature treatments because of enhanced transport of root-derived CTKs and stable panicle CKX activity. Our results provide insight into rice heat tolerance that will facilitate the development of rice varieties with tolerance to high temperature.

An Evaluation of Banana Macropropagation Techniques for Producing Pig Fodder in Northern Thailand

Smallholder farmers raising pigs in northern Thailand rely heavily on banana stalks as a fermented feed source, but struggle to reproduce banana plants fast enough to keep up with consumption. This study evaluated a variety of techniques for rapidly multiplying banana plants, using techniques appropriate and affordable to smallholder farmers in order to help meet this demand. Propagation techniques of Musa (ABB) cv. ‘Kluai Nam Wa’ were conducted in greenhouse and field experiments in both lowland and upland areas of Chiang Mai Province, Thailand. In greenhouse experiments, six treatments were conducted during the dry and rainy seasons, while five different treatments were compared in the field. Treatments used various methods of mechanical injury or application of benzyl aminopurine (BA) to induce plantlet differentiation. Number of plantlets to emerge, days to emergence, and circumference of plantlets were observed over a 90-day period. Results indicate that time of year plays an important role in the macropropagation of bananas, as significantly higher numbers of plantlets emerged during the rainy season. Plantlets emerged in 65 days, on average, during the dry season, but took only 54 days during the rainy season. During the rainy season, the presence of BA produced more plantlets than the other treatments, but during the dry season, there were no differences among treatments. Overall, the number of plantlets produced in all treatments evaluated was very low; however we believe this research is an important contribution to the literature and acknowledge that there exists significant opportunity to capitalize on the low-cost appropriate technology benefits that macropropagation of bananas can deliver to smallholder farmers.

Exogenous Application of Growth Enhancers Mitigate Water Stress in Wheat by Antioxidant Elevation.

The present study was conducted to investigate the response of two wheat cultivars (AARI-11 and Millat-11) to a foliar application of four growth enhancers which include: {H2O (water), MLE30 (moringa leaf extract), KCl (potassium chloride), and BAP (benzyl-amino purine)}, within the six irrigation water-regimes which are applied at the various critical growth stages such as crown root initiation (CRI), tillering (T), booting (B), and heading (H). Irrigation water-regimes include: CRI+T+B, CRI+T, CRI+B, T+B, T+H, and control (CRI+T+B+H). The growth enhancers i.e., H2O, MLE30 (1:30), KCl (2%), and BAP (50 mg L−1) were applied @ 500 L ha−1 at tillering and heading stages. The results demonstrated some increased quantities of both enzymatic (superoxide dismutase, peroxidase, catalase) and non-enzymatic (ascorbic acid, phenol) antioxidants in leaves of AARI-11 when MLE30 was applied under T+B and T+H irrigation water-regimes. Similar results were also observed in the case of leaf chlorophyll “a” and “b” and K+ contents in both cultivars under control, T+B and CRI+T+B irrigation water regimes. AARI-11 produced the highest biological and grain yield, due to the application of MLE30 and BAP under control, CRI+T+B, T+B, and T+H irrigation water-regimes. However, KCl lagged behind among the treatments set for both cultivars under all the irrigation water-regimes. Foliar spray of MLE30 remained prominent growth enhancer and stresses mitigating agent under water deficit conditions particularly under T+B and T+H irrigation water-regimes. Moreover, economic analysis indicated that the foliar application of MLE30 is a cost effective and environment friendly strategy for the maximum yield and income.

Cytokinin-mitigation of salt-induced leaf senescence in perennial ryegrass involving the activation of antioxidant systems and ionic balance

Leaf senescence is one of typical symptoms of salt stress in higher plants. The objectives of this study were to examine whether salt-induced leaf senescence could be alleviated by exogenous cytokinin and to elucidate on the regulatory mechanisms of cytokinin for mitigating salt stress in plants. Perennial ryegrass (Lolium perenne cv. Pinnacle) plants were exogenously treated with 6-benzylaminopurine (25μM) for 3d prior to salt stress imposition and every 7 days during salt stress for 28 days (250mM NaCl) in growth chambers. Physiological indicators of leaf senescence, including visual turfgrass quality, leaf photochemical efficiency, leaf chlorophyll content, electrolyte leakage, malondialdehyde content, percentage of cell death, and reactive oxygen species production rate and content were evaluated. Leaf relative water content was also measured to indicate leaf hydration status. Salt stress caused significant declines in turfgrass quality, leaf photochemical efficiency, leaf chlorophyll content, and leaf relative water content, and significantly increased electrolyte leakage, malondialdehyde content, percentage of cell death, and reactive oxygen species rate and content. 6-benzylaminopurine application alleviated the adverse physiological effects of salt stress, which was associated with reactive oxygen species scavenging by increased activities of superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate reductase, and glutathione reductase and up-regulating gene expression levels for ascorbate peroxidase and glutathione reductase. Salt stress significantly decreased cellular K+/Na+ ratio and 6-benzylaminopurine application suppressed Na+ accumulation to maintain a higher K+/Na+ ratio associated with increased high-affinity K+ transporter expression. The results demonstrate that 6-benzylaminopurine effectively reduced salt-induced cellular damages by suppressing oxidative and ionic stresses in perennial ryegrass.

Effects of pectinase, BAP and dry storage on dormancy breaking and emergence rate of Crataegus pseudoheterophylla Pojark.

Germination rates of Crataegus pseudoheterophylla are low and may be restricted by the presence of a hard endocarp and embryo dormancy. We examined the effects of pectinase [0, 0.5, 1, or 2 % (w/v)], benzylaminopurine (BAP) (0, 100, 200, 400, or 500 mg l−1) and dry storage (6, 9, or 12 months), on water uptake percentage (WUP) and seedling emergence rates with the endocarp intact or removed. Following treatments, seeds were subjected to a cold–warm–cold–warm–cold alternating temperature stratification regime, and then germinated at 23 °C for up to 90 days. The highest germination percentage (GP) of 37.7 and 32.7 % were obtained in seeds without endocarp treated at 500 mg l−1 BAP and dry-stored seeds for 12 months, respectively. WUP imbibed (96 h) in seeds with and without endocarp was 26.7 and 39.4 %, respectively, and the highest WUP was achieved in a period of 12 months (81 %). These results revealed that the application of BAP, pectinase, and dry storage significantly increased GP in C. pseudoheterophylla, probably mainly through dormancy-mediated processes. The results of the study confirmed that the seeds were semi-permeable by water.

Optimization of Seed Potato (Solanum tuberosum L.) Tuber Dormancy and Sprouting Capacity through Integrated Gibberellic Acid and Benzylaminopurine Application

Lack of sprouted seed potato tubers at planting is a major drawbacks for potato production in Kenya as most potato varieties remain dormant longer than three weeks while the window of planting is two weeks. To develop strategies that can enhance earlier sprouting a study was done to determine the effects of application of gibberellic acid (GA) and benzylaminopurine (BA) either Original Research Article

Comparative Effects of Foliar Application of Gibberellic Acid and Benzylaminopurine on Seed Potato Tuber Sprouting and Yield of Resultant Plants

Seed potato tubers planted immediately after harvest is characterized by delayed plant emergence, poor establishment and low yields. Gibberellic acid (GA) and Benzylaminopurine (BA) or their combinations cause dormancy breakage though little information is available on their combined application to dormancy termination. The effects of foliar application of GA and BA on potato tuber sprouting and subsequent yield were studied. Three potato varieties with different tuber dormancy period; ‘Asante’ (short dormancy), Dutch Robyjn (medium dormancy) and ‘Kenya Sifa’ (long dormancy) were planted at National Potato Research Centre, Tigoni and sprayed with a factorial combinations of 0, 50, 100, 300 ppm GA and 0, 50, 75, 100 ppm BA separately and combined at the rate of 1000 lts/ha spray volume towards the end of maturation. The resulting tubers were put in diffuse light storage (DLS) and data on number, length and vigour of sprouts recorded. Sprouted seed tubers were subsequently planted and evaluated for both growth characteristics and yields. The data collected was subjected to analysis of variance and significantly different means were separated using Fisher’s protected least significant difference at p≤0.05. Higher rates of foliar application of GA+BA (300 ppm + 100 ppm) compared with the control (0 + 0) resulted in significant increase insprout length (cm), number of sprout/tuber, sprout vigour (score), and % sprouting from 3.24 to 7.02 and 3.84 to 9.03, 2.04 to 4.45 and 2.07 to 4.8, 1.7 to 3.06 and 1.63 to 3.23, 61.21to 86.67and 63.3 to 83.7 in Asante, 2.94 to 8.03 and 2.8 to 7.99, 1.84 to 5.24 and 1.87 to 4.76, 1.3 to 3.0 and 1.27 to 2.63, 50.61 to 92.7 and 52.7 to 85.7in Dutch Robyjn and 0.79 to 6.43 and 1.32 to 6.99, 0.61 to 3.49 and 0.79 to 3.33, 0.61 to 3.03 and 0.73 to 2.83, 22.12 to 85.76 and 28.3 to83.7 in Kenya Sifa after storage in 2008 and 2009 respectively. A combination of BA and GA resulted in significantly more growth than using only GA or BA alone at the same level. Similarly the subsequent tuber numbers per plant and yield (tons/ha) in resultant plants increased from 7.13 to 12.53 and 24.66 to 32.27, 6.93 to 10.47 and 16.73 to 23.37, and 5.63 to 9.6 and 17.53 to 30.13 in Asante, Dutch Robyjnand Kenya Sifa respectively. Combined application of GA + BA at varied rates can be used to improve sprouting characteristics of seed potato and yield of resultant plants.

Effects of combined or single exogenous auxin and/or cytokinin applications on growth and leaf area development in Epipremnum aureum

SUMMARYWe have analysed the effects of combined auxin and cytokinin treatments on whole plant growth and leaf development in Epipremnum aureum and compared both morphological and physiological variables to those obtained with a single hormone application. Rooted cuttings of E. aureum were sprayed with 0, 5, 50, or 100 mg I−1 indole-3- acetic acid (IAA) 7 d after transplanting. One week later, they were then sprayed with 0, 5, 50, or 100 mg I−1 benzylaminopurine (BAP). Whole plant growth, leaf development, carbon fixation, and leaf anatomy were recorded for 6 months after these sequential treatments. Following a single application of IAA or BAP, we observed an increase in the accumulation of whole-plant biomass, which reached a plateau at the highest concentration of either plant hormone. The promotion of growth was associated with increased rates of net C-assimilation and net photosynthesis, as well as with increased leaf thickness and the relative proportion of intracellular spaces in the mesophyll layer. The effect on leaves of applying both hormones, in different combinations and concentrations, resembled the results on whole plants obtained by spraying either the auxin or the cytokinin (at 50 or 100 mg I−1 BAP). Similarities in plant and leaf responses to the auxin and/or the cytokinin suggest that both hormones may act via the same pathway, which agreed with the well-known promotional effect of auxins on the development of new lateral roots, as root apices are the main site of cytokinin biosynthesis. Conversely, our results did not support the occurrence of a significant auxin-driven inhibition of cytokinin synthesis in root apices, at least for E. aureum, as reported in other species.

<b>Use of phytoregulators in overcoming macaw palm seed dormancy</b> - doi: 10.4025/actasciagron.v35i4.16385

The macaw palm is a tropical palm with significant potential for biofuel production; however, seed dormancy is a major factor limiting its agro-industrial use. The present study evaluated the effects of phytoregulators in overcoming macaw palm seed dormancy. We evaluated the effects of immersion in solutions of gibberellic acid (GA3) (0, 2000 and 5000 mg L-1) during two exposure times (24 and 48 hours), associated with the removal or maintenance of the opercular tegument, as well as the effects of the associations between GA3 (2000 mg L-1), indole-3-butyric acid (IBA) and benzylaminopurine (BAP) and the effects of repeated applications (one, two or five) of combinations of these phytoregulators. The seeds were sown in vermiculite and incubated in a humid growth chamber at 95 ± 5% relative humidity and 30°C for 18 weeks in all experiments. GA3 application and removal of the opercular tegument had positive effects on germination, but no significant differences were observed in immersion times for this phytoregulator. The application of IBA and BAP did not influence germination. The application of GA3 on five separate occasions gave the best results, with 41% germination at the end of the experiment.

The pea TCP transcription factor PsBRC1 acts downstream of Strigolactones to control shoot branching.

The function of PsBRC1, the pea (Pisum sativum) homolog of the maize (Zea mays) TEOSINTE BRANCHED1 and the Arabidopsis (Arabidopsis thaliana) BRANCHED1 (AtBRC1) genes, was investigated. The pea Psbrc1 mutant displays an increased shoot-branching phenotype, is able to synthesize strigolactone (SL), and does not respond to SL application. The level of pleiotropy of the SL-deficient ramosus1 (rms1) mutant is higher than in the Psbrc1 mutant, rms1 exhibiting a relatively dwarf phenotype and more extensive branching at upper nodes. The PsBRC1 gene is mostly expressed in the axillary bud and is transcriptionally up-regulated by direct application of the synthetic SL GR24 and down-regulated by the cytokinin (CK) 6-benzylaminopurine. The results suggest that PsBRC1 may have a role in integrating SL and CK signals and that SLs act directly within the bud to regulate its outgrowth. However, the Psbrc1 mutant responds to 6-benzylaminopurine application and decapitation by increasing axillary bud length, implicating a PsBRC1-independent component of the CK response in sustained bud growth. In contrast to other SL-related mutants, the Psbrc1 mutation does not cause a decrease in the CK zeatin riboside in the xylem sap or a strong increase in RMS1 transcript levels, suggesting that the RMS2-dependent feedback is not activated in this mutant. Surprisingly, the double rms1 Psbrc1 mutant displays a strong increase in numbers of branches at cotyledonary nodes, whereas branching at upper nodes is not significantly higher than the branching in rms1. This phenotype indicates a localized regulation of branching at these nodes specific to pea.

Subtilisin-like serine proteases involved in N remobilization during grain filling in wheat

The induction of two subtilisin-like proteases (P1 and P2) associated with stress-induced senescence in young plants was investigated in adult wheat plants during the grain-filling period. Western blot analysis of flag leaf extracts showed that P1 was induced very late in the life cycle of the plants (9 days post-anthesis) and that 7 days later it reached a 2.5-fold increase with respect to the initial value at anthesis. On the other hand, the P2 signal was already detected previous to anthesis and increased soon after anthesis, reaching a fourfold increase by the end of the grain-filling period. The induction of P1 and P2 temporally correlates with the degradation of the Rubisco small and large subunits in the flag leaf, as well as with nitrogen (N) accumulation in the ears. At the same time, a decrease in the endogenous concentration of the cytokinins isopentenyladenine and isopentenyladenosine (iP + iPA) in the leaves was observed. In detached leaves senescing in the dark, the levels of both proteases were affected by 6-benzylaminopurine application: the induction of P1 was completely prevented, whereas the induction of P2 was reduced. Our findings demonstrate that both P1 and P2 are expressed in leaves of adult plants and are induced during natural senescence. These results enable us to postulate their participation in N remobilization to developing grains during monocarpic senescence and their regulation by a cytokinin-mediated mechanism.

Brotação de gemas em secções de caule de abacaxizeiro 'smooth cayenne' tratadas com reguladores de crescimento

Avaliou-se a propagação ex-vitro do abacaxizeiro, 'Smooth Cayenne', utilizando-se de secções de caule tratadas com Ácido Giberélico (GA3) e 6-benzilaminopurina (BAP). O delineamento utilizado foi o fatorial fracionado do tipo (1/5)5³, com tamanho de secções, GA3 e BAP, e cinco níveis, num total de 25 tratamentos, que consistiram em combinações de secções de diferentes comprimentos (6; 8; 10; 12 e 14 cm) e concentrações (0; 100; 200; 300 e 400 mg L-1) de GA3 e BAP. Cada parcela constituiu-se de 50 secções. O BAP apresentou efeito positivo, e o GA3, efeito negativo sobre a percentagem de secções brotadas em avaliação realizada aos 28 dias após o plantio. O tamanho da secção, o GA3 e o BAP influenciaram no número de gemas brotadas por secção. Verificou-se efeito para as características: altura, massa fresca e massa seca da parte aérea, e massa seca das raízes das mudas avaliadas aos 123 dias após o plantio, em resposta ao tamanho das secções, GA3 e BAP, sendo o efeito positivo apenas para o tamanho das secções. Os maiores valores de massas fresca e seca de mudas são obtidos sem a aplicação de BAP e GA3 em secções de caule com 14 cm de comprimento.

Effect of surface application of benzylaminopurine before and during water deficit on herbage production and quality

Insufficient water availability is one of the most serious environmental stresses for a plant and can be a major limitation to herbage production in many regions. Plant hormones, such as cytokinins, have been reported to reduce the detrimental effects of low water availability in many different plant species. However, there is little research available concerning the effect on pasture grasses. The aim of the present study was to quantify the effect of surface applications of 6-benzylaminopurine (BAP) before and during water deficit on herbage growth and quality of perennial ryegrass–white clover pastures. Pastures fertilised with BAP were compared with unfertilised pastures and pastures receiving nitrogen. Exogenous BAP application did not significantly affect herbage production or quality relative to unfertilised pastures. Nitrogen fertiliser increased total herbage production, but had little effect on herbage quality compared with BAP. The failure of surface applications of exogenous BAP to improve herbage production or quality suggests that it is not an appropriate method to enhance plant tolerance to water deficit at the concentration applied in this study.

Benzylaminopurine Application on Two Different Apple Cultivars (Malus domestica) Displays New and Unexpected Fruitlet Abscission Features

It has been previously shown that abscission of apple fruitlets is preceded by an increase in ethylene evolution and in the amount of transcripts for 1-aminocyclopropane-1-carboxylate oxidase (ACO), an enzyme catalysing the final step in ethylene biosynthesis. These events are concomitant with shedding induction and chemical thinning. There are several thinners but their mode of action and efficacy is poorly understood. One of them is benzylaminopurine (BA), a cytokinin believed to act by enhancing vegetative activity and stressing the competition between shoots and fruitlets, thus leading to fruitlet shedding. Nevertheless, the specific mechanism of action of BA and the variable effect depending on apple cultivar (easy or difficult to thin) are poorly understood. Abscission, the amount of MdACO1 transcripts and other parameters were followed in immature apple fruits during the period of physiological drop. The cultivars studied were 'Golden Delicious' and the 'spur' type 'Red Delicious'. BA was used as a thinning agent and was sprayed 14 d after petal fall (DAPF). Fruitlets were divided into central (C) and lateral (L) fruitlet populations. Fruitlet size was significantly different between C and L fruitlets but it did not differ much between the populations within the same cultivar. C fruitlets were characterized by basal ethylene evolution while L fruitlets displayed an increase in hormone biosynthesis during abscission induction. Cluster composition evaluated by the L/C ratio differed in the two varieties, being almost unchanged throughout abscission induction in 'Golden Delicious' and progressively decreasing in 'Red Delicious'. Shoot growth activity evaluated at the end of the season indicated a possible connection with both the ongoing abscission and BA application. MDACO1 transcripts were mainly detected in L fruitlets and the accumulation was related to total abscission in 'Golden Delicious', while in 'Red Delicious' expression was observed in both C and L fruitlets. BA probably exerts its thinning effect through vegetative growth. In the 'spur' type 'Red Delicious' the chemical is ineffective, probably due to a limited action on shoot growth due to genetic characteristics. The amount of MdACO1 transcripts in seeds is a good indicator of abscission.