Fruit load and branch ring-barking affect carbon allocation and photosynthesis of leaf and fruit of Coffea arabica in the field

Abstract

Increasing fruit load (from no berries present to 25, 50 and 100% of the initial fruit load) significantly decreased branch growth on 5-year-old coffee (Coffea arabica L.) trees of the dwarf cultivar 'Costa Rica 95', during their third production cycle. Ring-barking the branches further reduced their growth. Berry dry mass at harvest was significantly reduced by increasing fruit load. Dry matter allocation to berries was four times that allocated to branch growth during the cycle. Branch dieback and berry drop were significantly higher at greater fruit loads. This illustrates the importance of berry sink strength and indicates that there is competition for carbohydrates between berries and shoots and also among berries. Leaf net photosynthesis (P(n)) increased with increasing fruit load. Furthermore, leaves of non-isolated branches bearing full fruit load achieved three times higher P(n) than leaves of isolated (ring-barked) branches without berries, indicating strong relief of leaf P(n) inhibition by carbohydrate demand from berries and other parts of the coffee tree when excess photoassimilates could be exported. Leaf P(n) was significantly higher in the morning than later during the day. This reduction in leaf P(n) is generally attributed to stomatal closure in response to high irradiance, temperature and vapor pressure deficit in the middle of the day; however, it could also be a feedback effect of reserves accumulating during the morning when climatic conditions for leaf P(n) were optimal, because increased leaf mass ratio was observed in leaves of ring-barked branches with low or no fruit loads. Rates of CO(2) emission by berries decreased and calculated photosynthetic rates of berries increased with increasing photosynthetic photon flux (PPF) especially at low PPFs (0 to 100 micromol m(-2) s(-1)). The photosynthetic contribution of berries at the bean-filling stage was estimated to be about 30% of their daily respiration costs and 12% of their total carbon requirements at PPF values commonly experienced in the field (200 to 500 micromol m(-2) s(-1)).

Cytology, biochemistry and molecular changes during coffee fruit development

“…Kumar and Tieszen (1976) estimated that green coffee berries could provide 100 % of their maintenance requirements and up to 30 % of their growth requirements through their own photosynthetic activity. In a more recent study, it was estimated that berries could produce about 30 % of their own daily respiration costs and contributed to approximately 12 % of their total carbon requirements (Vaast et al, 2005). Therefore, even if large long distance carbohydrate transfers occur in coffee trees (Cannell, 1971), the contribution of the pericarp to the coffee bean development is far from negligible.…”

Metabolismo de nitrogênio em dois sistemas de cultivo de café sob veranico da estação úmida

“…Para os cafeeiros mantidos a pleno sol, foi verificada maior concentração de carga de frutificação no terço médio da copa dos cafeeiros; para os cafeeiros arborizados, o maior pegamento de frutos foi observado no terço superior. Segundo Vaast et al (2005), em estudo realizado com cafeeiros de cinco anos de idade, cv. Costa Rica 95, o transporte de fotoassimilados para os frutos foi quatro vezes superior ao observado para os ramos durante o terceiro ciclo de produção da cultura.…”

Impacts of leaf age and heat stress duration on photosynthetic gas exchange and foliar nonstructural carbohydrates in Coffea arabica

“…Since fruit production is the strongest carbohydrate sink in C. arabica (Cannell, 1976) and competes with vegetative growth (Amaral, Matta, & Rena, 2001; DaMatta et al., 2007, 2008; Vaast et al., 2005), the lack of fruiting in the heat treatments should theoretically result in more NSC available for growth, storage, metabolic maintenance, and repair (Chapin, Schulze, & Mooney, 1990; Dietze et al., 2014; Kozlowski, 1992). This helps elucidate the patterns in total NSC and starch of the 45‐min group (Figure 5a,b).…”

“…Given that even short heat events can have substantial impacts on carbon gain (Filewod & Thomas, 2014), the predicted fluctuations in the duration of summer heat waves (Della‐Marta, Haylock, Luterbacher, & Wanner, 2007), and the paucity of studies manipulating heat stress duration, research on the effects of heat stress duration on physiological recovery and NSC dynamics is needed. NSC dynamics in C. arabica are tightly linked to sink demand from vegetative and reproductive growth (Chaves, Martins, Batista, Celin, & DaMatta, 2012; Génard et al., 2008; Ramalho et al., 2013), and many studies have investigated whether NSC levels regulate C. arabica photosynthesis (Batista et al., 2011; DaMatta et al., 2016; Franck, Vaast, Génard, & Dauzat, 2006; Ronchi et al., 2006; Vaast, Angrand, Franck, Dauzat, & Génard, 2005). However, to our knowledge, no study has investigated the impacts of heat stress‐induced reductions in photosynthesis as a cause rather than a consequence of NSC dynamics in C. arabica .…”