Jowkar, A. | Search bioRxiv

bioRxiv2024

The longevity of cut flowers of Iranian narcissus is affected by genotype, physiochemical characteristics and stem structural factors

Flower longevity is one of the critical factors in determining the quality of cut flowers. narcissus, a popular cut flower in Iran, is cultivated outdoors in the fall and winter. Despite numerous studies on extending the longevity of narcissus flowers, our understanding of internal changes in floral tissues during the postharvest period is limited. This study aimed to investigate the morphophysiological and biochemical changes in floral tissues during postharvest conditions in Iranian narcissus populations. Ten narcissus populations were collected from various regions of Iran and cultivated in a greenhouse. The harvested narcissus flowers were kept in vases containing distilled water. Flower longevity; physicochemical characteristics, such as relative solution uptake, electrical conductivity, relative water content, total protein, antioxidant enzyme activity, carotenoids, H2O2 and malondialdehyde; stem mucilage sugars; structural features of the stem and vascular bundles; and the number of bacteria in the vase solution were evaluated on the first and third days after harvest. The experiment was conducted in a completely randomized design with nine replications, and mean comparisons were performed via SPSS software. The longevity of flowers is influenced by genetic characteristics and floral tissues. The populations of Shahla from the Khusf region and Porpar from the Khafr region presented the greatest longevity, whereas white narcissus presented the shortest longevity. Compared with petal tissue, corona tissue has greater longevity because of its thicker structure, higher water retention capacity, lower production of free radicals, and stronger antioxidant defense system. The number of vascular bundles was significantly positively correlated with relative solution uptake. No vascular blockage was observed during the postharvest period, but stem cells collapsed on the third day of vase life, which seemed to affect water uptake. The reason for the lack of vascular blockage in the narcissus stem requires further research.

plant biology↗

bioRxiv2023

Fragrance and color production by corona and perianth tissues of Iranian narcissus genotypes (Narcissus tazetta L.)

Flower color, shape and scent are the most attracting factors for consumers in the floriculture industry. The most fragrant Iranian narcissi (Narcissus tazetta L.) grown in natural habitats are Shahla, Meskinak, and Porpar genotypes. The present study was conducted to evaluate the color, scent, and also their interaction separately in corona and perianth of eleven Iranian narcissus accessions, for a better understanding of the bio-physiological differences in these tissues. For this purpose, the volatile organic compounds (VOCs) were analyzed using Headspace GCMS (gas chromatography/mass spectrometry); and total carotenoid, color values, and tissue thickness were measured in both perianth and corona tissues. Sensory analysis for corona and perianth was also conducted to evaluate scent perception. Besides, the expression of genes related to scent and color in corona and perianth was evaluated. Moreover, epidermal cells of perianth and corona were assessed by polarized light and SEM microscopy. The two most abundant compounds in both tissues were E-{beta}-ocimene and benzyl acetate, respectively; among which the first compound was higher in perianth, while the second one was higher in corona. Among identified VOCs, -terpineol, acetic acid, 2-phenylethyl ester, -pinene, {beta}-myrcene, and limonene were detected in corona of all genotypes of N. tazetta; however, these compounds were not identified in perianth of every genotypes. In corona, the negative correlations between the measured values of E-{beta}-ocimene and carotenoid and also, between the expression level of ocimene synthase and PSY (Phytoene synthase) with DXR (1-Deoxy-D-xylulose 5-phosphate reductoisomerase) suggested that there might be a competition between carotenoids and monoterpenes precursors in the MEP (methyl-D-erythritol phosphate) pathway. Volatile organic compound, color, scent emission, fresh weight and thickness of tissue were different in perianth and corona; while the surface coverage (with epidermal conical cells) were similar in these tissues. The findings of this research illustrated clearly for the first time that while both perianth and corona play important roles in scent production, corona has a more distinguished role in greater production of scent and color in Iranian narcissus flowers.

plant biology↗