Changes in leaf anatomy and photosynthesis of micropropagated banana plantlets under different silicon sources

Abstract

The objective of this study was to verify the possible changes in leaf anatomy and photosynthetic characteristics of ‘Maçã’ (Silk) banana plantlets cultivated in vitro in the presence of different silicon sources. ‘Maçã’ (Silk) banana plantlets pre-established in vitro were transferred to MS medium containing 30 g L−1 sucrose, 1 mg L−1 NAA and 1.8 g L−1 Phytagel™ and 1.0 g L−1 of three different sources of silicon: Na2SiO3, K2SiO3 and CaSiO3. The control group was conduced without silicon addition. After 45 days, gas exchanges were measured in infrared gas analyser and the leaf anatomy and chlorophyll content were evaluated as well as the silicon content in plants. The presence of calcium and sodium silicates enabled higher levels of silicon in the leaves than in the roots, however, potassium silicate promoted higher levels of silicon in the roots. Plantlets grown in the presence of calcium silicate had a higher photosynthetic rate and chlorophylls content compared to other treatments. There was a thickening of the epidermis, increased stomatal density, thicker mesophyll, thicker palisade parenchyma and a higher proportion of palisade parenchyma in relation to spongy parenchyma in seedlings grown in the presence of calcium silicate than in the control and other treatments. Silicon promoted more functional features and greater adaptability of ‘Maçã’ (Silk) banana plantlets, and the calcium silicate is a more efficient source for the promotion of favorable features in the in vitro culture of this species.