Changes of endogenous hormones during ovary development in rhododendron delavayi × rhododendron sinofalconeri and rhododendron delavayi × rhododendron cyanocarpum

Abstract

Endogenous plant hormones (EPHs) play a key role in plant development coordination, including floral bud development and fruit growth. Studying of EPHs during ovary development is very important to understand the growth regulation in rhododendron, which is the most important economic ornamental woody plant in the world. In this study, cross-pollination was performed between Rhododendron delavayi as female parent with R. cyanocarpum and R. sinofalconeri as male parents. Concentrations of different EPHs were evaluated in ovary development during days after cross-pollination (DAPs) using the HPCL technique. Jasmonic acid (JA) and jasmonoyl-L-isoleucine (JA-Ile) content recorded as the highest endogenous hormone level suggesting the low temperature stress faced by the plants during their growth in the forest special during winter season (January). Concentrations of Indole-3-acetic acid (IAA) peaked on 25 DAPs in both species and decreased during further days. The ovary consisted of the highest abscisic acid (ABA) level on the cross-pollination day (0 DAPs) indicating its inhibition effect on Rhododendron fruit growth. The highest level of GA9, GA19 and GA4 was recorded on 17 DAPs whereas GA4, GA44 and GA20 contents indicated that GAs has an important role in ovary development for both studied species. In conclusion, although no significant differences were found in the ovary measurements between both species, highly significant variations were recorded in EPHs changes after cross-pollination indicating the influence of the two male parents’ genotypes. Our results in EPHs changes during ovary development opened a gate to find a new modern way for saving the rare Rhododendron plants.