Growth and Reproductive Phenology of Welwitschia Mirabilis Hook. F.

Abstract

Reproductive phenology, reproductive traits and the pre emergent reproductive success (PERS) of Welwitschia mirabilis were studied in plants growing in the Botanical Garden of Portici. The leaves grow throughout the year and growth is positively correlated to temperature and day length; at flowering, the growth rate slows down. The plants have a reproductive cycle lasting 9-10 months; male plants form more branches and strobili than females, female strobili are larger than male ones. Both male and female plants produce cones that differ in the color of the covering bracts. Plants produce a lot of seeds, but most of them are empty; therefore the seed/ovule ratio is low. Filled and empty seeds are morphologically similar; filled seeds have high vitality that is maintained for several years. As probable causes of the low seed/ovule ratio, both pollination and embryo abortion are taken into account; our observations lead us to believe that the embryo abortion hypothesis is more accurate. However, since each plant may produce a discrete number of cones and filled seeds are highly viable, ultimately Welwitschia appears to be a rather efficient plant in terms of pre emergent reproductive success.

Field evidence from Namibia does not support the designation of Angolan and Namibian subspecies ofWelwitschia mirabilisHook

“…Despite this lack of additional field evidence, numerous journal articles, books (e.g. Dilcher, 2005;DiSalvatore et al, 2013;Kunzmann, 2011, van Jaarsveld & Pond 2013 and websites (e.g. Anon, 2014;Earle 2012;Leuenberger, 2010;Porcher, 2010) now state that there are two subspecies of W. mirabilis.…”

Ephedra as a gymnosperm evo‐devo model lineage

“…Observed 1C‐values at each ploidy level (2x–8x) in 50 species of Ephedra show that diploid South American species ( Ephedra triandra and E. tweediana ) fall within the smaller end of the range (red arrowhead). Growth habit is represented with icons, and generation times are shown as approximate ranges (in years), where available (Burns & Honkala, 1965; Dallimore & Jackson, 1967; Di Salvatore et al, 2013; Wang et al, 2015; Whitmore, 1977 and references therein). Figure adapted from Ickert‐Bond et al (2020) [Color figure can be viewed at wileyonlinelibrary.com]…”

Study of Heavy Metals Concentration in Sewage Water of Different Areas Around Bikaner City

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