|Authors: ||R.G. Lopez, E.S. Runkle|
|Keywords: ||light quantity, plug, propagation|
Light intensity is often reduced during propagation of nonrooted herbaceous cuttings to minimize temperature and water stress, but the effects of light quantity on rooting and cutting growth have not been quantified for horticulturally important annuals that are vegetatively propagated.
Petunia Tiny Tunia ‘Violet Ice’ (Petunia ×hybrida) cuttings were propagated under a daily light integral (DLI) of 1.2 to 3.9 mol•m-2•d-1. DLI environments were created using no shade or 30, 55, and 70% woven shade cloth.
All cuttings were rooted in a glasshouse with overhead mist, maintained at 25 ºC with a vapor pressure deficit of 0.3 kPa.
A 12-h photoperiod was delivered using a 9-h natural day extended with light from soft-white fluorescent lamps.
Rooting and growth evaluations of cuttings were made 8, 12 and 16 d after stick.
Rooting and quality of cuttings increased when the DLI under which they were propagated increased.
For example, after 16 d of propagation an increase in DLI from 1.2 to 3.9 mol•m-2•d-1 decreased cutting shoot length from 6.3 to 4.1 cm, increased average root number from 17 to 36, and increased average length of the longest root from 9.4 to 12.9 cm.
Root and shoot dry weight of cuttings harvested after 16 d of propagation increased by 452% and 47%, respectively, as the DLI increased.
Therefore, the DLI during propagation should be properly managed to reduce rooting time and produce high quality rooted transplants.
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