Anatomical and Physiological Effects of Phytohormones on Adventitious Roots Development in Larix kaempferi × L. olgensis

Abstract

Adventitious root development is crucial for cutting propagation in hybrid larch. In the present study, semilignified cuttings of Larix kaempferi ϫ L. olgensis clones were used to study the morphological and anatomical changes during the different development stages and compare the changes in contents of endogenous phytohormone in two clones with evidently different rooting capacity (25-5 and 23-12), and the effects of exogenous Indole-3-Butyric Acid (IBA) on phytohormone content of a very low native rooting capacity clone (8-9) during the development of adventitious roots. The results showed that the development of adventitious root in semi-lignified cuttings involves three key stages: root cell dedifferentiation and division (14-18 DAC); meristem formation and development (25-35 DAC); root formation and elongation (50-55 DAC). The endogenous phytohormones play a key role during adventitious root development. For 25-5 and 23-12, the level of endogenous phytohormones, especially the ABA content, has an important effect on rooting capacity. For the effects of IBA on 8-9, except lower ABA content, the temporary peak of IAA on the 1 DAC was important for initiating the rooting process. The ratio of (IAA + GA 3 + ZR)/ABA can be used as an indicator of rooting capacity. The anatomical and physiological data described here for semi-lignified cuttings of L. kaempferi ϫ L. olgensis clones improves our knowledge of adventitious roots development. Our study will also benefit future research on examining the molecular mechanisms of the adventitious roots development in hybrid larch.

Transcriptome and proteome profiling of adventitious root development in hybrid larch (Larix kaempferi × Larix olgensis)

“…In this study, two clones of L. kaempferi × L. olgensis , 25-5 (strong rooting capacity) and 23-12 (weak rooting capacity), and two early stages of adventitious root development, the root cell dedifferentiation and division stage (14 DAC) and the root initial cell formation stage (25 DAC) [ 2 ], are selected to study the molecular basis of developmental regulation of adventitious root formation. All plant material used in this study was propagated at Dagujia forest farm in Liaoning province in northeastern China (longitude of 42°2'48''N, latitude of 124°47'48''E; altitude of 225–394 m; and annual average temperature of 5.6°C) [ 2 ]. A completely randomized block design with three replicates was used.…”

“…Larches are very useful for afforestation because of their fast juvenile growth [ 1 ]. Among the various larches, hybrids of Larix kaempferi × Larix olgensis are widely planted in the mountainous regions of northeastern China for their high-quality timber, their pest resistance, and their amenity value [ 2 ]. The use of rooted stem cuttings is becoming the most popular method to propagate these hybrids.…”

“…So, the two clones are good materials for studying the biological process of adventitious root formation. Additionally, we had examined the development process of adventitious roots in semi-lignified cuttings of hybrid larch [ 2 ], which consisted of three key stages: 14-18 days after cutting (DAC) for cell dedifferentiation and division; 25-35 DAC for meristem formation and development; 50-55 DAC for root formation and elongation. The early stages, 14 and 25 DAC, were crucial for the expression and regulation of rooting-related genes.…”