Abstract
This work describes the evaluation of morpho-physiological and biochemical changes in “MD-2” micro-propagated pineapple plants (Ananas comosus (L.) Merr.) grown after 30 days under low light intensity (LL, greenhouse light conditions at 250 μmol·m-2·s-1) or high light intensity (HL, field light conditions at 800 μmol·m-2·s-1). Gas exchange, leaf pH, protein content and superoxide dismutase activity (SOD) (EC 1.15.1.1) were measured every 3 h during one day. Chlorophylls content and succulence index (SI) were determined at 9 h. Results showed significant differences in CO2 exchange rates, with a maximum occurring at 6 h (3.00 and 8.25 μmol CO2 m-2·s-1 for leaves under LL and HL conditions respectively). Plants under HL conditions had higher CO2 uptake and lower pH values between 0 h and 6 h respective to LL plants. The maximum pH value was attained 3 h before in HL plants. Leaf SI was increased and chlorophyll content decreased by HL conditions. SOD activity was higher in plants under HL conditions, near doubling those of LL plants at 18 h (2.8 versus 1.5 U·mg-1 Protein respectively). Both groups showed a typical CAM phenotype, but it was stronger in HL conditions, which may confer these plants with a better acclimation to transfer to the field.
Highlights
Pineapple (Ananascomosus (L.) Merr.) is a perennial monocot plant belonging to the family Bromeliaceae, subfamily Bromelioideae, in the order Bromeliales
Pineapple plants grown under HL conditions increased the D-leaf width at thirty days, while D-leaf length did not show significant differences (Table 2)
D-leaf width increment, could be a response to high light intensity conditions, it is know that the D-leaf width of micro-propagated pineapple plants was increased to 3.5 cm at 60 days of planted in field [6]
Summary
Pineapple (Ananascomosus (L.) Merr.) is a perennial monocot plant belonging to the family Bromeliaceae, subfamily Bromelioideae, in the order Bromeliales. To attain a better survival rate and establishment on field, these plants need to be further acclimatized in greenhouses using different pots, substrates, fertilizer programs, controlled light intensity and temperature and other important factors until plants reach the appropriate size [10]. Besides C3 or CAM metabolism in pineapple plantlets was conditioned by a combination of low relative humidity, and high temperatures and light intensity during the 4 first weeks of ex vitro growth [13] [14]. The aim of this work was to examine some morphological, physiological and biochemical changes in micro-propagated pineapple, 5-month old plants, grown during thirty days under low or high photosynthetic photon flux, in a greenhouse or under field light conditions respectively
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