Influence of nutritional media and photoperiods on in vitro asymbiotic seed germination and seedling development of Dendrobium aqueum Lindley

Abstract

Dendrobium aqueum Lindley is an epiphytic orchid decreasing in nature owing to environmental disturbance and inherent lower germination rates of mature seeds. To conserve this species, in vitro asymbiotic media and photoperiod screening were experimented. Twenty asymbiotic orchid seed germination media were examined to get the optimal medium for germination and seedling development under 16/8 hrs photoperiod. Highest seed germination occurred in 1 / 2 MS medium (93.41%) followed by mMS (91.04%) and m ½ MS (90.23%) in 6 to 7 weeks. The biggest protocorms were observed in MS medium (788.8 µm) followed by ½ MS (615.60 µm). The yellowish embryos during germination exhibit varied colours from yellow to pale green, dark green, yellow, brown, black and white. MS, ½ MS, mMS, ½ mMS, and ¼ MS media only promote fully developed seedlings within 126 to 143 days. The influence of five different photoperiods with four media was also examined separately. 24/0 hrs (L/D) photoperiod provide highest germination (97.75%) on MS followed by ½ MS (96.01%). Dark Photoperiod 0/24 h (L/D) supports up to protocorm stage but with poor seedling growth. The well rooted seedlings were hardened and successfully reintroduced in its natural habitat with 56% survival rate.

Asymbiotic in vitro seed propagation of Dendrobium

“…Parthibhan et al 2012). a Imbibed, enlarged seeds (zygotic embryos) with testa, turned into green (photosynthetic) 920 after 15 days of culture.…”

“…However, green pod culture or immature seed germination involves the use of green, undehisced capsules, which are harvested 70 days after pollination, opened and seeds are inoculated on culture media (Soundararajan 2009; Table 1). The time required for seed germination ranges from 30 to 59 days (Alam et al 2002;Sunitibala and Kishor 2009;Parthibhan et al 2012). Green pod seeds grown on Robert Ernst medium (Ernst 1982), KP medium (Knop 1865), KC medium, Curtis medium (Curtis 1936) and Pfeffer (Harvais 1972) medium became pale green or whitish green and eventually produced weak seedlings but on VW medium, KC medium, Thomale GD medium (Thomale 1954), Mitra et al medium (Mitra et al 1976) and Wolter and Skoog medium (WS; Wolter 1968) the seeds became brown and could not germinate.…”

“…KC or modified KC media are usually used for Dendrobium seed germination (Table 1; Hu and He 1979;Xu and Yu 1984;Yu et al 2011). Parthibhan et al (2012) studied 20 basal media devoid of PGRs and additives for D. aqueum. Half-strength MS medium macronutrients, to which 2 % sucrose was added, resulted in highest seed germination (93.41 %) and seedling development.…”

“…ex Lindl., D. hookerianum Lindl., D. longicornu Lindl., D. nobile, D. parishii Rchb.f.) are also flamed(Dohling et al 2008;Hajong et al 2010;Vasudevan and Van Staden 2010;Dutta et al 2011;Kaewduangta and Reamkatog 2011;Parthibhan et al 2012;Paul et al 2012;Hossain 2013;Nongdam and Tikendra 2014)…”

Influence of Photoperiod and Culture Medium on the Speed of Asymbiotic Seed Germination and Seedling Development in Spathoglottis plicata

“…Comparative results were found with Calopogon tuberosus, where seeds at an advanced stage (Stage 6) were only observed under light incubation (Kauth et al, 2006). Similarly, although light was not a limiting factor for early stages of seed germination, it was essential for subsequent seedling development in Dendrobium aqueum (Parthibhan et al, 2012). The authors observed that the 0/24-h light/dark photoperiod supported seeds up to the protocorm stage with poor seedling growth; seedling development occurred only when longer photoperiods were used.…”