Defoliation and Fruit Removal Effects on Papaya Fruit Production, Sugar Accumulation, and Sucrose Metabolism

Abstract

<jats:p>Papaya (<jats:italic>Carica papaya</jats:italic> L.) source size and sink strength were modified by a single defoliation or continual defoliation and fruit thinning. Fruit set, development, weight, total sugar (sum of sucrose, fructose, and glucose), sucrose phosphate synthase (SPS), sucrose synthase (SS), and acid invertase (AI) enzyme activities in response to defoliation and fruit thinning were determined. The effects of defoliation and fruit thinning varied with weather conditions, plant growth conditions, and cultivar. Removal of 75% of the leaves significantly reduced new flower production and fruit set, and decreased ripe fruit total soluble solids (TSS), while 50% defoliation did not reduce new fruit set or ripe fruit TSS. When every third leaf from the oldest leaf was not removed, the number of new flowers was reduced by 47% more than when the same number of leaves was removed from the oldest to younger leaves. Continual removal of old leaves reduced new fruit set, fruit weight, and TSS in the 168 day experimental period. Fruit thinning increased new fruit set and ripe fruit TSS. Larger fruit size, faster fruit development, lower respiration rate, and higher sugar contents and AI activity were observed in immature (young) fruit when old fruit were removed. AI activity was reduced during early fruit development and increased again in mature fruit in plants subjected to defoliation, and suggested a role for AI in mature fruit sugar accumulation, while SS activity declined significantly in fruit 154 and 175 days after anthesis and in mature fruit when plants were subjected to continual defoliation. SPS activity was not affected significantly by defoliation or fruit thinning. Source-sink balance was critical for papaya fruit set, development, and sugar accumulation and each mature leaf was able to provide photoassimilate for about three fruit.</jats:p>

Metabolic variation between japonica and indica rice cultivars as revealed by non-targeted metabolomics

“…In addition, four seed metabolites (stachydrine, mannitol, arabinol, and arabitol) negatively correlate with filled seed number per panicle (FSNPP) but two metabolites (1-MGPC and 1-OGPC) positively correlate with ESNPP, revealing the competition for nutrition among the seeds in the same plant. The similar competitive phenomenon was observed in other species including badamu46, apple47, citrus48, papaya49, and tomato50. Furthermore, two seed metabolites (GPC and mannitol) negatively correlate with plant height.…”

Root Development of Bell Pepper (Capsicum annuum L.) as Affected by Water Salinity and Sink Strength

“…Successful plant growth and reproduction depend on adequate partitioning of the resources among roots, shoots and reproductive organs. Source and sink metabolism are tightly coordinated and large fluctuations and imbalances between supply and demand are avoided [1][2][3]. At the early stages of plant development, assimilates are partitioned between shoots and roots.…”

Herencia de la concentración de los sólidos solubles entre líneas parentales de papaya (Carica papaya L.) y sus híbridos

“…Sin embargo, debe tomarse en cuenta también que la relación fuente-sumidero también tiene un efecto importante sobre el nivel de brix de la fruta de esta especie. En este sentido, Zhou et al (2000) alteraron esta relación mediante tratamientos de defoliación y raleo de frutas, con lo cual comprobaron que un mayor índice "área foliar / kg de fruta" correlacionaba también con una mayor concentración de sólidos solubles finales en la fruta. Es importante notar que dicho índice también correlacionó positivamente con una mayor actividad de la invertasa ácida, reforzando la posibilidad de que dicha enzima esté implicada en la determinación final de los sólidos solubles de la fruta.…”

“…La mayoría de plantas con grandes superficies de área foliar tienen una capacidad fotosintética mayor a una determinada carga de frutas, lo cual se traduce en mayores niveles de sólidos solubles de sus frutas (Hubbard et al 1990). Esta correlación se ha cuantificado para varias especies frutales tales como kiwi, mango, manzana, grapefruit y ciruela (Zhou et al 2000).…”