In vitro morpho-histological studies of newly developed embryos from abnormal malformed embryos of date palm cv. Gundila under desiccation effect of polyethelyne glycol treatments

Abstract

Substantial progress has been made toward micropropagation of date palm species by somatic embryogenesis. Routine production faced disadvantage due to persisting problems with the efficiency of embryo maturation and conversion. This was attributed to the formation of somatic embryos with numerous morphological abnormalities. The present paper was conducted to study the desiccation effect of poly ethylene glycol (PEG) in relation to embryo maturation, and germination. Abnormal malformed embryo explants were cultured on germination medium supplemented with different concentrations of PEG (15, 20 and 25gl−1) for two periods (15, 30days) as desiccation treatments. Clear significant changes showed de novo organs as newly direct somatic embryos (secondary embryos). These embryos could be germinated with shoot formation from all desiccated abnormal somatic embryo explants with PEG treatments. The addition of PEG at 20gl−1 to germination medium for 30days gave the highest significant number of newly direct somatic embryos comparing with other treatments. Finally secondary somatic embryos converted to full plantlets. For the first time histological investigation was made to reveal anatomical development of secondary embryos from abnormal malformed embryos under (PEG) treatments. The first step showed numerous meristematic multicellular centers occurring before treatment with (PEG). These centers may serve as an inactive source of embryoids. Some morphological and histological changes were recorded during (PEG) treatments and determined by special developmental stages (2-celled, 4-celled, globular and bipolar embryos with normal structure) of new somatic embryos of date palm. The presented data strongly supported that the osmotic stress caused by different concentrations of PEG activates the process of morpho-ontogenetic events to develop new healthy somatic embryos.