Effects of growth retardants on sprouting and development of apricot (Prunus armeniaca L.) and neem (Azarchta indica A. Juss.) nodal buds

Abstract

As a first step to the establishment of an in vitro conservation protocol for apricot and neem, the effect of several growth retardants on the sprouting and development from nodal buds of both species and meristem development at the histological level was evaluated. Nodal section bud sprouting was affected by growth retardants, ranged from 4 to 100 % in apricot and from 10 to 100 % in neem, depending on the retardant and its concentration. Retardants paclobutrazol (PBZ), flurprimidol (FMD), diniconazole (DIN), and acetyl-salicylic acid (ASA) produced a drastic reduction of shoot length in apricot. PBZ, DIN and ASA decreased the number of leaves, whereas 1-Aminocyclopropane-1-carboxylic acid (ACC) at 10−5 µM improved the number of leaves. Length of neem sprouted buds as well as the number of leaves was affected by all of the growth retardants, with the exception of ACC that only affected the number of leaves. Triiodobenzoic acid (TIBA) at 10−5 µM improved neem shoot length. PBZ, FMD, and DIN produced several effects as very thin, long, and dark green colored leaves in shoots from both species. Once growth retardants were removed from the proliferation medium the recovery of apricot bud growth was good from PBZ and FMD at low and medium concentrations and from ACC and ASA at all concentrations tested. In neem, the recovery was good only from TIBA and ASA at low concentrations; TIBA at 10−5 µM produced an increment of shoot length higher than the control. Histological changes observed in the meristems of apricot and neem buds during growth retardation induced by FMD and ASA could be related to some extent with those observed in the dormant shoot apex.