Varying leaf-to-fruit ratios affect branch growth and dieback, with little to no effect on photosynthesis, carbohydrate or mineral pools, in different canopy positions of field-grown coffee trees

Abstract

a b s t r a c tHeavy bearing is a typical phenomenon on unshaded coffee (Coffea arabica L.) trees and limits both the production and retention of leaves, leading to branch dieback, and, thus, results in a strong biennial bearing pattern. The major goals of this study were to investigate the physiological mechanisms that may be associated with the leaf-to-fruit ratio (LFR), branch dieback, biennial production and the relationships between carbohydrate and mineral fluctuations and branch dieback in coffee plants. The trees were grown in north-south-oriented hedgerows under conditions of full sunlight. Leaves and plagiotropic branches from the upper and lower strata of the east-and west-facing sides of the hedgerow were examined. A strong biennial pattern of coffee production was observed over three harvests. Overall, the east face of the hedgerow produced a more sellable crop than the west face, and this was associated with more light availability for the east-facing branches. The branch growth rate was higher with an increasing LFR during 2006-2007, regardless of the canopy position, and no compensatory increase in the photosynthetic rate was found in response to a decreasing LFR. Due to a relatively low fruit yield in 2007-2008, there was no branch dieback. The extent of branch dieback increased dramatically with decreasing LFR and was probably not closely related to changes in the concentrations of carbohydrates, amino acids and minerals. The extent of branch dieback was apparently unrelated to the differences in the photosynthetic rates per unit leaf area, carbon isotope composition, or oxidative stress, as was assessed by the electrolyte leakage from the leaf tissues. We discuss these responses in terms of the relative lack of branch autonomy in coffee trees.

<b>Vegetative growth of Conilon coffee plants under two water conditions in the Atlantic region of Bahia State, Brazil

“…This result was certainly associated with the grain formation stage of the coffee plants, when the requirement for nutrients is high. As fruits constitute preferential sinks for nutrients and photoassimilates (Laviola et al, 2008;Partelli, Espindola, Marré, & Vieira, 2014), vegetative growth is severely jeopardized during this stage, due to an accentuated imbalance in the source:sink ratio of these productive branches, despite these branches (PlagBB) possessing limited autonomy in the production and supply of carbohydrates, as verified for C. arabica (Chaves, Martins, Batista, Celin, & DaMatta, 2012). Additionally, the advent of new branches (budding) may reduce the growth of older branches (Ferreira et al, 2013) due to the changes in the source:sink relationship among different branches.…”

Morphophysiological plasticity of plagiotropic branches in response to change in the coffee plant spacing within rows

“…This means that there was a higher dry matter partitioning for fruits over leaves and branches, and this was clearly confirmed by the linear increase in the fruit mass ratio (Figure 2 According to Cannell (1985), 20 cm 2 of leaf is required for each coffee fruit. However, Chaves et al (2012) showed that branch growth and total fruit production are reduced as RAFRr decreases, showing competition between vegetative and reproductive growth, the latter prevailing over the former, since fruits are priority sinks (CANNELL, 1985;LAVIOLA et al, 2007). In this study, the strong effect of spacing on RAFFr was demonstrated.…”

“…However, Chaves et al (2012) showed that branch growth and total fruit production are reduced as RAFRr decreases, showing competition between vegetative and reproductive growth, the latter prevailing over the former, since fruits are priority sinks (CANNELL, 1985;LAVIOLA et al, 2007). In this study, the strong effect of spacing on RAFFr was demonstrated.…”

“…Taken together, these results indicate that in denser crops, the marked lower yield per plant, also verified by Rena et al (2003) and Andrade et al (2014) is accompanied by a more appropriate leaf area: fruit ratio, therefore characterizing an increase in the source: sink ratio. This can contribute to lower production biannually and higher longevity of plants in denser crops, as suggested by DaMatta et al (2007), also reducing the occurrence of dry branches, whose incidence is known to be lower in branches with higher RAFFr (CHAVES et al, 2012). Figure 2.…”

“…Morphophysiological changes have been observed in coffee in response to environmental variations (NASCIMENTO et al, 2006;FERREIRA et al, 2013;PEREIRA et al, 2013;RODRÍGUEZ-LÓPEZ et al, 2014), especially variation of light intercepted by branch leaves in different canopy positions (ARAUJO et al, 2008;MATOS et al, 2009;CHAVES et al, 2012). Reduction in the planting spacing both between rows and between plants in a row resulted in greater height of the primary orthotropic branch (RENA et al, 2003;CUNHA, 2004;PAULO et al, 2005), lower stem diameter and canopy base (PAULO et al, 2005), caused more intense necrosis of plagiotropic branches in the lower third of the coffee plant (MATIELLO et al, 2010;CUNHA, 2004), and decreased the productive area of each plant CUNHA, 2004), justifying the fact that disuse of spacing below 0.5 m between plants in the row.…”