An efficient method of propagation of Podophyllum hexandrum: an endangered medicinal plant of the Western Himalayas under ex situ conditions

Abstract

This study shows an effective but simple method of conserving characterized populations and elite clones through vegetative propagation and genetic diversity through seeds in Podophyllum hexandrum (family Berberidaceae). Seed dormancy has been considered to be a major constraint in these seeds and most of the earlier reports recommended dormancy-breaking pretreatments such as chilling, gibberellic acid (GA(3)), etc. However, seeds of the 14 accessions that we tested exhibited no dormancy and hence did not require any pretreatments. Besides accession, collection of seeds with high moisture content could be one of the reasons for lack of dormancy. Thus, we propose germination of seeds (while they still retained moisture) in sand at 25 degrees C for high and reproducible results within a shorter period of time compared with earlier reports. Hypocotyl dormancy is known to considerably delay plant establishment and hence en masse propagation by preventing the emergence of functional leaves for up to 11-12 months. Manual removal of cotyledonary leaves, being labor and time intensive, is not a feasible method for large-scale seedling establishment. However, in this study, we showed that GA(3) at 200 ppm can alleviate hypocotyl dormancy besides reducing the time taken for true or functional leaf emergence. Treatment of cotyledonary leaves of 1 week-old-seedlings with 200 ppm GA(3 )resulted in true or functional leaf emergence within 7 days, and the resultant plants were also more vigorous than the ones obtained from manual removal of cotyledonary leaves. The study helped advance the establishment of seedlings by one growing season (almost 1 year).

Factors affecting podophyllotoxin yield in the ex situ grown Podophyllum hexandrum, an endangered alpine native of the western Himalayas

“…The highest amounts of PDT were recorded in the belowground parts of 2-year-old plants harvested during LGP. Although this amount is much lower than that of in situ plants, i.e., 1.2 versus 1.96 [12], the difference in yield can be easily met by producing a large number of plants using our earlier reported protocol [7]. Interestingly, the 3-yearold plants with maximum biomass of below-ground parts did not yield the highest amounts of PDT.…”

“…The plant avoids, rather than tolerates its harsh environmental conditions by strictly synchronizing its growth with seasonal variations in temperature [6]. It has also been shown that P. hexandrum can be grown ex situ at lower temperate altitudes [7]. However, its growth behavior, and the right age and time of harvesting the below-ground parts under ex situ conditions are yet to be identified.…”

Methyl jasmonate treatment increases podophyllotoxin production in Podophyllum hexandrum roots under glasshouse conditions

“…The soil study (sand versus peat-perlite) was performed at both temperatures with 30 plants for each soil type. Sand and peat-perlite were previously described to be successful for P. hexandrum, respectively for the germination of seeds and in transplanting of rootlets into soil (Kharkwal et al 2008;Guo et al 2012). For statistical analysis, a factorial design was used with three factors: soil, temperature and time.…”

Xyloglucan endo-transglycosylase/hydrolase (XET/H) gene is expressed during the seed germination in Podophyllum hexandrum: a high altitude Himalayan plant

“…1 filter paper moistened with aqueous solution of phytohormones (250 lM: V/V) or water (for control) according to Sharma et al (2006) and Kharkwal et al (2008) in Petri plates at 20 ± 1°C for overnight. After that, the seeds were shifted on to filter papers (Whatman No.…”

“…In Podophyllum, slow and delayed germination is due to the structural barriers around the embryo (Sreenivasulu et al 2009), or the absence of specific components required for radicle elongation or both. Earlier studies on Podophyllum seed germination reports that the GA enhances the germination by removing physiological, morphological, or morpho-physiological dormancy (Kandari et al 2007;Sharma et al 2006 andKharkwal et al 2008). In seeds, as an adaptive measure to sustain the unfavoring conditions, ABA induces and then maintains the dormancy which leads to the delayed germination (Bewley and Black 1994).…”