Comparative floral morphology and anatomy of Anacardiaceae and Burseraceae (Sapindales), with a special focus on gynoecium structure and evolution

Abstract

Anacardiaceae and Burseraceae are traditionally distinguished by the number of ovules (1 vs. 2) per locule and the direction of ovule curvature (syntropous vs. antitropous). Recent molecular phylogenetic studies have shown that these families are sister groups in Sapindales after having been separated in different orders for a long time. We present a comparative morphological study of the flower structure in both families. The major clades, usually supported in molecular phylogenetic analyses, are well supported by floral structure. In Anacardiaceae, there is a tendency to gynoecium reduction to a single fertile carpel (particularly in Anacardioideae). The single ovule has a long and unusually differentiated funicle, which connects with the stylar pollen tube transmitting tract in all representatives studied. In Anacardiaceae-Spondiadoideae, there is a tendency to form an extensive synascidiate zone, with a massive remnant of the floral apex in the centre; these features are also present in Beiselia (Burseraceae) and Kirkiaceae (sister to Anacardiaceae plus Burseraceae) and may represent a synapomorphy or apomorphic tendency for the three families. In core Burseraceae, gynoecium structure is much less diverse than in Anacardiaceae and has probably retained more plesiomorphies. Differences in proportions of parts of the ovules in Anacardiaceae and Burseraceae are linked with the different direction of ovule curvature.

Identification of zygotic and nucellar seedlings in polyembryonic mango cultivars

“…Moreover, unlike citrus embryos of mature seed, which are easily separated and individually cultured in vitro (Andrade-Rodríguez et al, 2004, 2005, mango embryos of mature seed cannot be separated without causing lesions. Consequently, it is possible that, during seed formation, embryos develop under different dynamics in the two species, especially if we consider apomixis is a type of facultative reproduction that responds to the conditions to which they are adapted (Andrade-Rodríguez et al, 2005;Batygina & Vinogradova, 2007).…”

“…Seedlings MeM-1 and MeM-2 were identified as nucellar, since they exhibited the same banding pattern as the mother plant. In these seeds, it is possible that the zygotic seedling was not detected because it degenerated, leaving the nucellar embryo to develop freely in the entire seed loculus (Batygina & Vinogradova, 2007). Another probable explanation is pointed out by Andrade-Rodríguez et al (2005) for monoembryonic seeds of Citrus reshni and "Robinson" (C. clementina x Tangelo Orlando): they may have been zygotic, but identical to or differing little from the mother plant due to self-pollination.…”

“…The embryo next to the point of insertion of seed funiculus in the seed coat was denominated 'one'; the rest were arranged counterclockwise and then numbered. The funiculus was used as the reference, since in anatropous ovules, such as mango, it is next to the micropyle (Bachelier & Endress, 2009). Fresh matter weight (mg), length (mm, from the tip of the radicle to the opposite tip of the largest cotyledon) and width (mm, measured at the widest part, perpendicular to length, including the two cotyledons) were recorded for each embryo (64 embryos of 'Manila', and 54 embryos of 'Ataulfo').…”

“…Therefore, in polyembryonic crops, the identification of the zygotic embryo has great importance (Villegas & Andrade, 2008). Moreover, nursery plant producers can use the nucellar embryos to propagate disease-free clone rootstocks (Soares Filho et al, 2003;Santos et al, 2010), or rejuvenate old clones that have lost their vigor through constant vegetative propagation (Batygina & Vinogradova, 2007;Villegas & Andrade, 2008).…”

“…Despite the relevance of several apomictic genera, such as Euphorbia, Mangifera, Malus, Ribes, Beta, Panicum, Brachiaria, Dichanthium, and Pennisetum (Bicknell & Koltunow, 2004), most studies on embryogenesis and polyembryony have been done on citrus; therefore, this genus has been considered the model for both processes (Batygina & Vinogradova, 2007). However, results obtained with citrus have been extrapolated to other species, leading to possible erroneous interpretations.…”