. 2022 Mar 22;11(7):844. doi: 10.3390/plants11070844

Table 2.

Summary of the use of LED lighting in in vitro propagation of woody species.

Studied Species/Explant Type	Light Intensity and Photoperiod	Light Spectra	Growth Regulators in Medium	Results on In Vitro Proliferation	Morphogenetic Response	Authors and Year
Pseudotsuga menziesii Mirb. Douglas fir embryo	0.01–0.71 W/cm² 16 h photoperiod	8 different narrow bandwidth Fl having maxima each at one of the following wavelengths 371, 420, 467, 504, 550, 590, 660, and 740 nm.	Embryo from seeds; For callus induction: 800 pg L⁻¹ IAA, 1 mg L⁻¹ IBA, 1 mg L⁻¹ BA, 1 mg L⁻¹ AS-isopentyladenine After four weeks, 0.5 mM BA and 0.25 mM zeatin were added. No growth regulators for growing buds.	Callus and adventitious bud formation on the embryo-derived callus was maximum at (0.42 mW/cm⁻²) under RL (660 nm).		[122]
Woody ornamental plants. Organogenesis (axillary bud proliferation)		Fl (control), high pressure sodium lamps (HPS), BL and RL	Light pipe modified growth chambers	HPS increased shoot number as compared to FL. RL increased shoot number over control.		[123]
Spirea nipponica Maxim/Shoot explants from 8 to 10 week-old stock cultures	WL: low fluence 15.0–23.0; high fluence 47.0–62.0 µmol m⁻² s⁻¹; RL+FR: low fluence) 8.7–15.9 µmol m⁻² s^−l 16 h photoperiod	WL, RL + Fr	BA 0.25, 0.4, or 0.5 mg L⁻¹.	RL + FR = improved proliferation especially by 0.5 Ba addition. RL + FR followed by high fluence WL improved proliferation at lower BA levels.	RL + Fr favourably influenced shoot length and growth	[124] No LEDS
‘Mr.S 2/5’ clone of Prunus domestica Ehrh./Cuttings;	WL = 38.0 BL = 9.1 RL = 19.6 FR = 7.2 µmol m⁻² s⁻¹	WL BL RL FR	Ba 0.6 mg L⁻¹	In intact cuttings, WL gave the highest shoot proliferation In decapitated seedlings, all lights gave 100% bud outgrowth.	BL and WL = a higher number of nodes; RL = longer internodes. Shoots produced in RL were longer in decapitated seedlings.	[125] all experiments were repeated twice
Cydonia oblonga Mill/Leaves from the second to the fourth node of the apical portion of in vitro shoots	BL, WL and RL = 20 ± 1; FR = 1.2 R + B 10 + 10 B + Fr= 20 + 1.2 Fr + RL = 0.5 + 1.6 (µmol m⁻² s⁻¹)	D, BL, WL, FRL, RL, RL+Bl, BL+FRL RL+FRL After All light treatments, further 20 days of WL light exposure.	4.7 µM K and 0.5 µM NAA	Somatic embryogenesis was highest under RL treatment.		[126] No LEDS
Prunus avium L. cv ‘Hedelfinger’and one of its somatoclones/Leaves	~9 µmol 16 h photoperiod	WL, RL, BL, FR, D	2 mg dm³ TDZ+ 2,4-D or IAA	WL and BL = the highest node number. BL and FR = the highest shoot outgrowth from buds.	RL = highest shoot length under. WL and BL and WL= high chlorophyll.	[127] no LEDS
Malus domestica [Suckow] Borkh. genotype MM106/Shoot tips from in vitro cultures	~40 μmol m⁻² s⁻¹ 16 h photoperiod	WL, RL, BL, GL, YL, UV-AL, D	8.86 (2 mg L⁻¹) µM BA, 0.53 (0.06 mg L⁻¹) µM Ga₃, 0.3 µM (0.1 mg L⁻¹) IBA	GL and WL gave the higher total number of shoots at the end of the fourth culturing cycle.	Leader stem height was greater under D, RL and YL.	[128] No LEDs Four cycles
Populus alba × P. berolinensis/Stems from in vitro shoots	40 µmol m⁻² s⁻¹ 16 h photoperiod	GL, RL, BL and YL. Fl (control)	0.02 mg·L⁻¹ NAA, and 0.1 mg·L⁻¹ TDZ.	Fl and YL exhibited better effects on shoot regeneration		[129] no LEDs
Musa spp. cv.’Grande naine’ AAA)/Meristematic shoot tips	40 μmol m⁻² s⁻¹ 16 h photoperiod	WL, Fl	16.8 μM BAP, 3.8 μM IAA, 1 mg L⁻¹ on a temporary immersion system (TIS)	WL under TIS enhanced shoot proliferation.		[130]
Populus x euramericana selected clones, ‘I-476’ and ‘Dorskamp’/Petioles (5-mm long) from in vitro plants	60 μm m⁻² s⁻¹ 16 h photoperiod	Fl, BL, RL, RL +BL (1:1 and 7:3), and RL + BL + GL (7:2:1)	0.44 µM BA	Highest shoot regeneration on RL + BL (1:1) for ‘I-476’, on BL +RL (7:3) for ‘Dorskamp’ as compared to Fl.	High RL (100% or 7:3) = higher shoot length and leaf area BL or RL +BL (7:3) = higher stem diameter	[131]
Malus domestica [Suckow] Borkh rootstock cvs. Budagovsky 9 (B.9), Geneva 30 (G.30), and Geneva 41 (G.41). I exp = single-node segments	BL = 5.7 RL = 6.6 WL = 25 μmol·m⁻²·s⁻¹	WL, RL, BL for both experiments	1.0 mg·L⁻¹ BA, 0.1 mg·L⁻¹ IBA, and 0.5 mg·L⁻¹ GA₃. II exp: cv. G.30 with and without gibberellic acid (GA3).	RL increased the number of shoots in B.9 and G.30 as compared to WL.	RL increased the length, and the number of elongated shoots of B.9 and G.30. GA₃ promoted shoot growth of G.30 under RL and BL.	[132] No LEDS
Phoenix dactylifera L. cv. ‘Alshakr’ (Date palm)/shoot buds	20–25 μmol m⁻² s⁻¹ 14 h photoperiod	FL (control), RL +BL (18:2) (CRB-LED)	1 mg L⁻¹ (NAA), 0.5 mg L⁻¹ (BA) and 0.5 mg L⁻¹ kinetin (K)	CRB enhanced the percentage of buds producing shoots and average shoots formation compared to FL	CRB-LED enhanced total soluble carbohydrates, starch, free amino acids, and peroxidase activity	[133]
Camellia oleifera C. Abel/Axillary buds	50 m⁻² s⁻¹ 16 h photoperiod	RL, BL, RL + BL, (4:1) RL + BL (1:4), WL was used as control	3.0 mg L⁻¹ BA + 0.02 mg L⁻¹ IBA	RL + BL (4:1) = the highest proliferation coefficient.	RL + BL (4:1) = good chlorophyll content, the thickest leaves, high stomatal density.	[134]

Abbreviations: white (WL), blue (BL), red (RL), far-red (FRL), dark (D), fluorescent light (Fl), NAA (1-Naphthaleneacetic acid), BA (6-Benzylaminopurine), IAA (Indole 3- Acetic Acid), 2,4-D (2,4-dichlorophenoxyacetic acid).