The use of different LEDs wavelength and light intensities on in vitro proliferation of cherry rootstock: influence on photosynthetic pigments, photosystem II photochemistry and leaf anatomy

Abstract Plant growth and development are strongly influenced by light quality conditions in their environment. In this study, shoot proliferation, photosynthetic pigments, leaf anatomy and photosystem II photochemistry of Gisela 6 cherry rootstock (Prunus cerasus x Prunus canescens) were investigated. Initially, three light wavelength absorption spectra including 400–700 nm (mainly blue-green, White Fluorescent Light, WFL), 450–550 nm (mainly blue-red: BR, LED2) and 450–660 nm (blue-green-yellow-orange-red, LED3) under 40 µmol m− 2 s− 1 intensity were studied. Following that, three Light Emitting Diodes (LED) intensities including 20 (LED1), 40 (LED2), and 120 µmol m− 2 s− 1 (LED4) were investigated under BR spectrum. The culture medium used was the MS (Murashige and Skoog) containing 4.4 µΜ 6-benzyladenine (BA), 0.05 µΜ α-naphthalene acetic acid (NAA) and 0.3 µM gibberellic acid (GA3) (30 days, 16h photoperiod, 22 ± 2 oC). WFL exhibited non-significant differences with LED2 (shoot number 4.25, proliferation rate 4.30, shoot height 0.91 cm). LED2 displayed higher fresh and dry shoot biomass, better PSII functionality, increased Chl a/b, Chl b and carotenoids content, avoiding oxidative damage as evidenced by the decreased stressed explants (5.36%). Leaf anatomy under LED2 and WFL was similar. LED4 presented the highest rate of stressed explants, with their leaf anatomy being severely affected, as leaves had a reduced mesophyll cell density. In LED4, the proportion of the absorbed energy used in photochemistry (ΦPSII) was decreased whereas the increased quantum yield of non-regulated energy loss in PSII (ΦNO) could not be compensated by the increased photoprotective energy dissipation (ΦNPQ). Therefore, LED2 was the most beneficial for growing Gisela 6 plantlets in vitro.