Application of GA3 and girdling of branches on the production of extemporaneous fruits of 'Tahiti' acid lime

Abstract

Aplicação de GA 3 e anelamento de ramos na produção de frutos extemporâneos de limeiras ácidas 'Tahiti'Objetivou-se, neste trabalho, avaliar os efeitos do anelamento de ramos e da aplicação de GA 3 , ainda na florada da safra principal, sobre a formação de estruturas reprodutivas, o pegamento e a produção de frutos da florada subsequente, extemporânea, de limeira ácida 'Tahiti'. Utilizou-se o delineamento experimental em blocos casualizados, com cinco repetições, em esquema fatorial 4 x 3. O primeiro fator foi a aplicação foliar de GA 3 , 88 dias antes da florada extemporânea, nas concentrações (0, 7, 14 e 21 mg.L -1 ). O segundo fator foram as épocas de anelamento, 108 dias antes do início do florescimento (A108AF), 78 dias antes do florescimento (A78AF), mais a testemunha, sem anelamento (SA). Na florada extemporânea, as proporções de botões florais, flores e frutos que sofreram abscisão foram de 38,75; 31,25 e 18,64%, respectivamente, e foram colhidas 11,34% de todas as estruturas reprodutivas formadas. O GA 3 não alterou o pegamento. O anelamento aumentou o pegamento dos frutos em 229 e 256%, aos A108DAF e A78DAF, respectivamente, em relação às plantas SA. O GA 3 reduziu a formação de estruturas florais, fato que propiciou aumento, de forma quadrática, da produção, por reduzir a concorrência por fotoassimilados entre os frutos, sendo a concentração de 21 mg.L -1 a mais produtiva, com 15,97 frutos.planta -1 .Palavras-chave: giberelina, floração, estruturas reprodutivas, floema. Application of GA 3 and girdling of branches on the production of extemporaneous fruits of 'Tahiti' acid limeThe objective of this study was to evaluate the effect of girdling of branches and the application of GA 3 , still in the main crop flowering on the formation of reproductive structures, the fruit set of the following extemporaneous flowering of 'Tahiti' acid lime. This work used a randomized block design with five replications in a 4x3 factorial design. The first factor was the foliar application of GA 3 , 88 days before extemporaneous flowering at five concentrations (0, 7, 14 and 21 mg.L -1 ). The second factor was the girdling times, 108 days before flowering onset (A108AF), 78 days before flowering (A78AF) plus no-girdling control (NG). In extemporaneous flowering, the proportion of buds, flowers and fruits that abscised was 38.75, 31.25 and 18.64% respectively and 11.34% of all reproductive structures formed were collected. GA 3 did not affect fruit set. Girdling increased fruit set by 229 and 256% at A108DAF and A78DAF respectively, in relation to NG plants. The GA 3 reduced the formation of floral structures, which resulted in a quadratic increase in field production by reducing the competition for photoassimilates among fruits. The concentration of 21 mg.L -1 was the most productive, with 15.97 fruit.plant -1 .

Gibberellic acid in Citrus spp. flowering and fruiting: A systematic review

“…In most of the reviewed studies (Fig 8), exogenous GA applications during the induction period consistently reduced flower formation [85,87,89,90,97,98,106,102,107–111], while the application of Paclobutrazol (PBZ), a known antagonist of GA, increased the number of flowers [90,108]. As when temperature and water stress were manipulated for floral induction, GA also affected inflorescence type.…”

“…Most experiments were performed on young trees (Fig 5) under very controlled conditions and with repeated GA applications. GA applications were performed at any time during the induction period with good results, even on days before flowering [85,87,89,90,97,98,106,102,107–111]. It has been suggested that this technique can be used to mitigate alternate bearing in “on” years or to merely control the constant heavy flowering of some varieties [106,112].…”

“…GA has also been applied upon petal fall and some weeks later to improve fruit set with very variable results [13,83,96,98,108,114–118]. Many experiments have reported enhanced initial fruit set, but this effect was transient and the final yield did not increase in most cases [114,115,119,120].…”

Productivity of Citrus latifolia plants subjected to branch girdling

“…Despite the absence of statistical difference, a trend towards increased foliar concentration of carotenoids in plants with 100% girdling is evident. Accumulation of carbohydrates in the canopy may cause retroinhibition of photosynthesis, hinder CO 2 assimilation and cause oxidative stress (Pereira et al, 2014;Rivas et al, 2007). Under such circumstances, carotenoids take on photoprotective importance, as they remove the reactive species that cause oxidative stress.…”

“…Girdling prevents assimilation from being transported to the root system, increasing temporary retention of carbohydrates in the tree canopy and thus promoting greater fruit fixation (Santos et al, 2014). According to Pereira et al (2014), girdling increases the number and size of C. latifolia fruit. Despite the benefits of girdling, the incision into the stem may cause accumulation of phytoregulators and other metabolites, bringing undesired effects such as reduced plant size, lower photosynthesis rate, yellowing leaves and reduced root growth (Pereira et al, 2010(Pereira et al, , 2011.…”