Environment, photosynthesis, and adventitious rooting of manchurian lilac cuttings propagated in overhead mist, submist, and combination systems

Abstract

We propagated manchurian lilac (Syringa pubescens subsp. patula 'Miss Kim') vegetatively from stem cuttings using overhead mist, submist, and combination propagation systems. Cuttings were collected when terminal buds were already set, after the period of tender growth that is optimal for lilac propagation. Net photosynthesis (Pn) was recorded to assess whether differences in rooting could be attributed to differences in photosynthetic activity of cuttings within each system. The propagation environment differed significantly among systems, with vapor pressure deficit (VPD) substantially greater for submist systems than for overhead mist or combination systems, and root zones warmer in submist and combination systems than in overheadmist. Pn of cuttings did not differ among systems and was initially low, but increased about when the first root primordia were visible. Rooting percentageswere 90%among cuttings in the combination system, with cuttings in overhead mist and submist rooting at lower, but similar, percentages (68% and 62%, respectively). Cuttings in the combination and submist systems produced significantly more and longer roots than those in the overheadmist system, and retained nearly all of their leaves. Overall, the use of systems that provide intermittent mist to the basal end of each cutting was effective for propagating manchurian lilac. Our results demonstrate that cuttings in submist alone experience a much greater VPD than those in overhead mist, but may nonetheless root at comparable percentages and produce superior measures of root system quality. Combination systems show promise for rooting of species like manchurian lilac, because cuttings rooted at high percentages and with consistent root systemquality, despite having been collected after the optimal spring period for lilac propagation.