Morpho-physiological and phytohormonal changes during the induction of adventitious root development stimulated by exogenous IBA application in Magnolia biondii Pamp

Alterações morfofisiológicas e fito-hormonais durante a indução do desenvolvimento radicular adventício estimulado pela aplicação exógena do AIB em Magnolia biondii Pamp

Abstract

Magnolia biondii Pamp is an important ornamental tree species widely grown and used as a rootstock in the propagation of different Magnolia varieties. In the current studies, anatomical, physiological and endogenous hormones were studied to check the effect of IBA 750 mg/L on the adventitious rooting and to provide theoretical and technical support for the propagation of Magnolia biondii Pamp through stem cuttings. Two thousand stem cuttings were prepared and divided into two groups i.e., IBA treated cuttings and water control. For the evaluation of antioxidant enzyme activities, and endogenous hormones levels, samples were collected on the day of planting and each 5^th day and further steps were carried out in the laboratory according to the protocols and proper precautions. For the anatomical observations, samples were collected on the 13^th, 15^th, and 17^th day for IBA treated cuttings while 21^st, 23^rd, and 25^th day for control. Collected samples were preserved in the FAA solution and further observations were carried out in the laboratory. Anatomical observations showed that it took 13 days for the differentiation of root primordia to the appearance of young adventitious roots in IBA treated cuttings, while it took 21 days to develop primordia in the control. Antioxidant enzyme activities involved in ROS were significantly higher in the IBA treated cuttings compared to control. POD showed a peak on the 13^th day before the emergence of roots in IBA treated cuttings while it showed a peak on the 21^st day in the control. PPO showed a peak on the 21^st day in the IBA treated cuttings while it showed a peak on the 29^th day in the control. SOD showed a peak on the 17^th day in IBA treated cuttings, while it showed a peak on the 25^th day in the control. Exogenous application of IBA enhanced the endogenous IAA and GA₃ levels compared to CK, while it reduced the levels of ABA continuously at the time of rooting and then increased gradually. Inclusively, our study suggests that IBA 750 mg/L is efficient for the rooting of Magnolia biondii Pamp cuttings, as it enhanced the process of antioxidant enzyme activities, endogenous hormones levels and reduced the time of root formation which is evident from the anatomical observations.

Keywords:
Magnolia biondii Pamp; antioxidant enzyme activities; endogenous hormones; anatomical observations; adventitious rooting; stem cuttings