Differential usage of storage carbohydrates in the CAM bromeliad Aechmea ‘Maya’ during acclimation to drought and recovery from dehydration

Abstract

CAM requires a substantial investment of resources into storage carbohydrates to account for nocturnal CO(2) uptake, thereby restricting carbohydrate partitioning to other metabolic activities, including dark respiration, growth and acclimation to abiotic stress. Flexible modulation of carbon flow to the different competing sinks under changing environmental conditions is considered a key determinant for the growth, productivity and ecological success of the CAM pathway. The aim of the present study was to examine how shifts in carbohydrate partitioning could assure maintenance of photosynthetic integrity and a positive carbon balance under conditions of increasing water deprivation in CAM species. Measurements of gas exchange, leaf water relations, malate, starch and soluble sugar (glucose, fructose and sucrose) contents were made in leaves of the CAM bromeliad Aechmea 'Maya' over a 6-month period of drought and subsequently over a 2-month period of recovery from drought. Results indicated that short-term influences of water stress were minimized by elevating the level of respiratory recycling, and carbohydrate pools were maintained at the expense of export for growth while providing a comparable nocturnal carbon gain to that in well-watered control plants. Longer term drought resulted in a disproportionate depletion of key carbohydrate reserves. Sucrose, which was of minor importance for providing substrate for the dark reactions under well-watered conditions, became the major source of carbohydrate for nocturnal carboxylation as drought progressed. Flexibility in terms of the major carbohydrate source used to sustain dark CO(2) uptake is therefore considered a crucial factor in meeting the carbon and energy demands under limiting environmental conditions. Recovery from CAM-idling was found to be dependent on the restoration of the starch pool, which was used predominantly for provision of substrate for nocturnal carboxylation, while net carbon export was limited. The conservation of starch for the nocturnal reactions might be adaptive with regard to responding efficiently to a return of water stress.

Functional types in the Bromeliaceae: relationships with drought‐resistance traits and bioclimatic distributions

“…Across the major functional types within the family, there is a relatively modest capacity for osmolyte accumulation (i.e. high values of p o ) and osmotic adjustment, consistent with some earlier studies (Smith et al 1986;Nowak & Martin 1997;Martin et al 2004;Ceusters et al 2009). Bromeliads are therefore rather drought sensitive at the cellular level compared with other plant groups (e.g.…”

“…; Ceusters et al . ). Bromeliads are therefore rather drought sensitive at the cellular level compared with other plant groups (e.g.…”

Specific leaf areas of the tank bromeliad Guzmania monostachia perform distinct functions in response to water shortage

“…In addition, the drought-induced establishment of CAM-idling in G. monostachia occurred extremely rapid when compared to other bromeliads. For example, in the bromeliad Aechmea 'Maya', a typical CAMidling state occurred only after 150 d of water stress (Ceusters et al, 2009), while in G. monostachia practically no CO 2 uptake was detected after one week of water shortage (Fig. 3).…”

Light quality modulates metabolic synchronization over the diel phases of crassulacean acid metabolism

“…These major CAM phases are punctuated by Phase II at the start of the day and Phase IV at the end of the day (Borland and Taybi, 2004). All four phases of the CAM cycle show plasticity in terms of magnitude and duration, which seems to be critical for optimizing carbon gain and water use under different environmental situations (Ceusters et al ., 2008a, 2009a, 2009b, 2010, 2011; Dodd et al , 2003). …”