In situ observations of the basal angiosperm Amborella trichopoda reveal a long fruiting cycle overlapping two annual flowering periods

Abstract

Amborella trichopoda is the sole living angiosperm species belonging to the sister lineage of all other extant flowering plants. In the last decade, the species has been the focus of many phylogenetic, genomic and reproductive biology studies, bringing new highlights regarding the evolution of flowering plants. However, little attention has been paid to in situ A. trichopoda populations, particularly to their fruiting cycle. In this study, an A. trichopoda population was observed during three annual flowering cycles. Individuals and branches were labeled in order to monitor the fruiting cycle precisely, from the flowering stage until the abscission of the fruit. Fruit exocarp was green during the first 9 months following flowering, turned red when the next flowering started a year later then remained on the branch during another year, between fruit ripping and abscission. Presence of fruits with two stages of maturity on shrubs was always noticed. Germination tests showed that seeds acquired their germination capacity 1 year after flowering, when fruits changed color. A. trichopoda's fruiting cycle is a long process overlapping two annual flowering periods. These results introduce a new model for flowering and fruiting cycles. The availability of mature seeds on shrubs for more than 1 year is likely to maximize opportunities to be dispersed, thus promoting the survival of this basal angiosperm.

A Combination of Histological, Physiological, and Proteomic Approaches Shed Light on Seed Desiccation Tolerance of the Basal Angiosperm Amborella trichopoda

“…Mature Amborella drupes were collected at a mature stage [ 23 ] from individual trees located at “Plateau de Dogny-Sarraméa” in the central mountain range of New Caledonia. The fleshy part of the fruits was removed before sensu stricto seed isolation.…”

The morphophysiological dormancy inAmborella trichopodaseeds is a pleisiomorphic trait in angiosperms

“…Secondly, our findings contribute to a growing picture of the ecophysiology of A. trichopoda within its endemic habitat of the New Caledonian rain forest. We thus add data on seed dormancy and germination to studies of photosynthesis (Feild et al, 2001), stomatal function (Rudall and Knowles, 2013), vascular function (Feild et al, 2000;Turgeon and Medville, 2011;Feild and Wilson, 2012), flowering time (Fourcade et al, 2015), pollination biology (Thien et al, 2009), seed physiology (Poncet et al, 2015), population structure (Thien et al, 2003;Poncet et al, 2013) and genetic diversity (Poncet et al, 2012). These diverse studies of A. trichopoda make a major contribution to the concerted reconstruction of the ecophysiological features of the first flowering plants (see Feild et al, 2004;Feild and Arens, 2007).…”

“…The mature A. trichopoda embryo is short and broad (Bailey and Swamy, 1948;Tobe et al, 2000), suggesting the possible presence of MD. Fourcade et al (2015) refer to unpublished studies of germination and dormancy in this species, though no detailed work has previously been undertaken.…”

Prolonged embryogenesis in Austrobaileya scandens (Austrobaileyaceae): its ecological and evolutionary significance

“…It can range from c . 2 to 3 months in Schisandra (Grushvitzky, ; Nikolaeva et al ., ; Zhou & Wang, ; Chien et al ., ) to 3 months in Amborella (Fourcade et al ., ; Fogliani et al ., ), and 4 months in Illicium (Thien et al ., ; Olsen & Rutter, ). Seeds of Nymphaeales show a much more variable time to germination.…”