Stock plant etiolation and immersion in IBA solution stimulate rooting capacity of Pinus patula cuttings

Abstract

Cloning by rooted cuttings from individuals with low adventitious root-forming capacity depends on multiple factors such as light exposure during cutting development and immersion time in indole-3-butyric acid (IBA) solution. This study evaluated the effects of stock plant etiolation on total soluble sugars concentration and endogenous growth regulators profile, and its combined effect with exogenous IBA application on rooting capacity of Pinus patula cuttings. Early morpho-anatomical changes related to root formation were also assessed. A first trial evaluated immersion time of cuttings (0, 15, 30, 60, 120, and 240 s) in a 5000 ppm IBA liquid solution. Afterwards, the combined effect of stock plant etiolation (0, 3, and 6 days) with IBA application (0 and 120 s immersion) was tested. Cuttings were rooted under controlled conditions (20–24°C and 85–100 % relative humidity) for twelve weeks. Variables measured included the percentage of live cuttings, callus formation, rooted cuttings, number of primary roots, length of the longest root, average primary root length, and percentage of rooted cuttings with secondary roots. Both trials showed over 98 % survival. IBA-immersion for 120 s achieved 83.6 % rooted cuttings. In the second trial, six-day etiolation with IBA-application produced the highest rooting (64.4 %) with more and longer primary roots, and 70.7 % secondary root presence. Etiolation reduced sugar content and increased endogenous auxin levels in cuttings compared to non-etiolated ones. Changes in soluble sugars and growth regulators due to etiolation enhanced root formation. Controlling these parameters provides an operational protocol for efficient cloning of Pinus patula .