Physiological and biochemical abilities of robusta coffee leaves for acclimation to cope with temporal changes in light availability

Abstract

The effects of varying intensities of light on plants depend on when they occur, even if the total amount of light received is kept constant. We designed an experiment using two clones of robusta coffee (Coffea canephora) intercropped with shelter trees in such a way that allowed us to compare coffee bushes shaded in the morning (SM) with those shaded in the afternoon (SA), and then confronting both with bushes receiving full sunlight over the course of the day (FS). The SM bushes displayed better gas-exchange performance than their SA and FS counterparts, in which the capacity for CO2 fixation was mainly constrained by stomatal (SA bushes) and biochemical (FS bushes) factors. Physiological traits associated with light capture were more responsive to temporal fluctuations of light rather than to the amount of light received, although this behavior could be a clone-specific response. The activity of key antioxidant enzymes differed minimally when comparing the SM and SA clones, but was much larger in FS clones. No signs of photoinhibition or cell damage were found regardless of the light treatments. Acclimations to varying light supplies had no apparent additional cost for constructing and maintaining the leaves regardless of the light supply. Both the SM and SA individuals displayed higher return in terms of revenue streams (e.g. higher mass-based light-saturated photosynthetic rates, photosynthetic nitrogen use efficiencies and long-term water use efficiencies) than their FS counterparts. In conclusion, shading may improve the physiological performance of coffee bushes growing in harsh, tropical environments.

Tobacco guard cells fix CO2 by both Rubisco and PEPcase while sucrose acts as a substrate during light‐induced stomatal opening

“…; Rodríguez‐López et al . ). These results suggest that guard cells are either fixing the carbon needed to produce the osmoticum required to open the stomatal pore via photosynthesis or alternatively have stored this carbon in another form, most likely in the vacuole, during the previous dark period.…”

“…2). Given that the epidermal fragments were harvested pre-dawn, this fast stomatal opening may be related to the circadian clock of the stomatal opening of plants growing under tropical conditions, in which rapid stomatal opening is observed in early morning (Antunes et al 2012;Rodríguez-López et al 2013). These results suggest that guard cells are either fixing the carbon needed to produce the osmoticum required to open the stomatal pore via photosynthesis or alternatively have stored this carbon in another form, most likely in the vacuole, during the previous dark period.…”

Vegetative growth and yield of robusta coffee genotypes cultivated under different shading levels

“…Regarding to effects of shade on vegetative growth and yield of coffee plants, studies have reported that shade causes an increased leaf area (RODRÍGUEZ-LÓPEZ et al, 2013), decreases in branch emission (MORAIS et al, 2006), increases in the internode distance (ANIM-KWAPONG et al, 2010), and etiolation of the plagiotropic and orthotropic branches (ARAÚJO et al, 2016). About the production of Coffea canephora under shading, few studies were performed in field conditions, even that exist a demand for this information, leaving a gap of uncertainties to the coffee producer that pretends to have a coffee plantation shaded.…”

Climatic Vulnerability in Robusta Coffee Mitigation and Adaptation

“…higher efficiency in the use of nitrogen, and water, and enhanced potential net photosynthesis) (Machado Filho et al, 2012;Rodríguez-López et al, 2013), probably related to the reduction of temperature and irradiance level, as well as with an increase in air relative humidity . Figure 16.…”

“…Several works have reported that this system management might promote micro-meteorological changes, namely, by reducing (i) direct irradiation, (ii) wind velocity, (iii) air temperature, (iv) water vapor pressure deficit between the air and the leaf; which altogether would increase the water availability (DaMatta et al, 2003;2007b;2010;DaMatta 2004;DaMatta and Ramalho, 2006;Pezzopane et al, 2008;2011;Rodríguez-López et al, 2013). For instance, the positive effects of shading have been associated with the decrease of incident radiation on the canopy, reducing the extension of the photo-oxidative damages, the velocity of the wind and the temperature of the air (up to 5 ºC).…”