Mollo 2015 (Conference Paper) Alcantarea, Rocky Outcrops

PEPC and MDH activity in Alcantarea imperialis (Carriere) Harms cultured in vitro with polyethylene glycol ? PEG 6000

Author(s):—Luciana Mollo & Catarina Nievola in Benko-Iseppon, A.M.; Alves, M. & Louzada, R. (2015) An overview and abstracts of the First World Congress on Bromeliaceae Evolution. Rodriguésia 66(2): A1-A66.

Publication:— (2015).

Abstract:—Plant species from rupicolous environments are adapted to temperature variations and to low water availability,as is the case of the ornamental bromeliad Alcantarea imperialis, known as imperial bromeliad, native to the Serra dos Órgãos (RJ, Brazil), a montane tropical rainforest area with ?Campos de Altitude?. It grows on rocky outcrops (inselbergs), in shallow and stony soils and is exposed to episodes of water shortage. Under this condition, plant species can express the CAM pathway, induced by the absence of water. The goal of this study was to analyse the activity of phosphoenolpyruvate carboxylase (PEPC) and malate dehydrogenase (MDH) enzymes in A. imperialis plants cultured in vitro under water-deficit conditions, simulated with different polyethylene glycol (PEG 6000) concentrations, in order to verify if this species can express the CAM pathway when exposed to such conditions. Plants were obtained through seed germination in Murashigue & Skoog culture medium with macronutrient concentration reduced to half, 30 g L-1 of sucrose and 7 g L-1 of agar. After 6 months, plants were transferred to the same media, without agar and with PEG in concentrations of 0% (T1, with -0.5 MPa); 7.5% (T2, with -1.9 MPa); 30% (T3, with -4.7 MPa); 45% (T4, with -8.5 MPa);and 60% (T5, with -17 MPa) during 7, 15 and 30 days in a growth chamber under 26 ºC ± 4 ºC and 12 h photoperiod. Plants were analysed in terms of biometric parameters, PEPC and MDH activities. No differences were observed in biometric parameters between treatments. However, results indicated that longer exposure to water-deficit conditions led to a gradual increase in PEPC and MDH activities, which could be involved with this species adaptation to water-deficit conditions, although no expression of CAM could be confirmed in plants cultivated at any of the PEG concentrations applied.

Keywords:—Photosynthesis; C3; Pepc.