Articles
Effect of light quality and PGR sprays on rooting and growth of young plants propagated indoors
Article number
1423_25
Pages
185 – 194
Language
English
Abstract
Propagation of unrooted cuttings (URC) and tissue-cultured (TC) explants in controlled environments with sole-source lighting can help reduce crop losses (shrinkage) and shorten rooting times for greenhouse (GH) finishing.
However, unknowns exist about the optimal environmental setpoints for indoor propagation.
Our objective was to compare growth and rooting of chrysanthemum (Chrysanthemum × grandiflora) and lavender (Lavandula × intermedia) URC and coral bells (Heuchera × villosa) TC explants propagated under different light qualities indoors or in a GH, with or without sprays of a plant growth regulator (PGR) (daminozide (Dz) at 1,000 mg L‑1) used to counteract potential negative light-quality effects on stem elongation.
Indoors, a photosynthetic photon flux density of 70 µmol m‑2 s‑1 was provided for 20 h d‑1 by monochromatic blue (B) light-emitting-diode fixtures (LEDs) or by broadband white LEDs with or without 35 µmol m‑2 s‑1 of far-red radiation (WFR or W, respectively). In general, plants sprayed with Dz were shorter but produced less shoot and root dry mass (DM) than those without PGR, suggesting that at early rooting stages, PGR sprays may negatively affect root growth and quality.
Light-quality responses showed that chrysanthemum cuttings were tallest and had the highest shoot DM under WFR, but root DM was highest when cuttings were propagated in the GH. Lavender propagated under WFR and B were taller and tended to produce more shoot and root DM than under W or in the GH. In general, shoot and root growth were higher in coral bells propagated indoors than in the GH, and differences were particularly noticeable in unsprayed plants.
Overall, our results show that although indoor propagation provided some rooting advantages compared to GH propagation, growth responses to the different light-quality treatments were inconsistent among the three plant species.
In addition, although WFR and B provided rooting advantages during the initial propagation phase, differences in growth became smaller after a carryover phase.
However, unknowns exist about the optimal environmental setpoints for indoor propagation.
Our objective was to compare growth and rooting of chrysanthemum (Chrysanthemum × grandiflora) and lavender (Lavandula × intermedia) URC and coral bells (Heuchera × villosa) TC explants propagated under different light qualities indoors or in a GH, with or without sprays of a plant growth regulator (PGR) (daminozide (Dz) at 1,000 mg L‑1) used to counteract potential negative light-quality effects on stem elongation.
Indoors, a photosynthetic photon flux density of 70 µmol m‑2 s‑1 was provided for 20 h d‑1 by monochromatic blue (B) light-emitting-diode fixtures (LEDs) or by broadband white LEDs with or without 35 µmol m‑2 s‑1 of far-red radiation (WFR or W, respectively). In general, plants sprayed with Dz were shorter but produced less shoot and root dry mass (DM) than those without PGR, suggesting that at early rooting stages, PGR sprays may negatively affect root growth and quality.
Light-quality responses showed that chrysanthemum cuttings were tallest and had the highest shoot DM under WFR, but root DM was highest when cuttings were propagated in the GH. Lavender propagated under WFR and B were taller and tended to produce more shoot and root DM than under W or in the GH. In general, shoot and root growth were higher in coral bells propagated indoors than in the GH, and differences were particularly noticeable in unsprayed plants.
Overall, our results show that although indoor propagation provided some rooting advantages compared to GH propagation, growth responses to the different light-quality treatments were inconsistent among the three plant species.
In addition, although WFR and B provided rooting advantages during the initial propagation phase, differences in growth became smaller after a carryover phase.
Authors
M. Retana-Cordero, C. Gómez
Keywords
cuttings, LEDs, propagation, plant growth regulator, tissue culture, vertical farming
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