Jasna Dolenc Koce

Genome size of Adriatic seagrasses

Genome size (C-value) was measured in four species of Adriatic seagrasses with interphase-peak DNA image cytometry. The estimated 2C-value was 1.5 pg DNA for Zostera noltii (2n = 12), 1.2 pg for Zostera marina (2n = 12), 1.1 pg for Cymodocea nodosa(2n = 28) and 6.2 pg for Posidonia oceanica, using Pisum sativum(2C-value = 8.84 pg) as the calibration standard. Seagrass leaves were fixed in 4% buffered formaldehyde to mitigate stoichiometric error due to tannins and post-fixed in 3:1 methanol:acetic acid (MAA). DNA was stained with the Feulgen reaction after hydrolysis in 5 M HCl for 90 min at 20 ◦ C. Comparison of genome size of seagrasses with the data for other species of Alismatidae indicated that the ancestral genome of Alismatidae was relatively small.

A cellular study of teosinte Zea mays subsp. parviglumis (Poaceae) caryopsis development showing several processes conserved in maize

The evolutionary history of maize (Zea mays subsp. mays) is of general interest because of its economic and scientific importance. Here we show that many cellular traits described previously in developing caryopses of maize are also seen in its wild progenitor teosinte (Zea mays subsp. parviglumis). These features, each with a possible role in development, include (1) an early programmed cell death in the maternal placento-chalazal (P-C) layer that may lead to increased hydrolytic conductance to the developing seed; (2) accumulation of phenolics and flavonoids in the P-C layer that may be related to antimicrobial activity; (3) formation of wall ingrowths in the basal endosperm transfer layer (BETL); (4) localization of cell wall invertase in the BETL, which is attributed to the increased transport capacity of photosynthates to the sink; and (5) endoreduplication in endosperm nuclei suggested to contribute to increased gene expression and greater sink capacity of the developing seed. In maize caryopsis, these cellular traits have been previously attributed to domestication and selection for larger seed size and vigor. Given the conservation of the entire cellular program in developing teosinte caryopses described here, we suggest that these traits evolved independently of domestication and predate human selection pressure.

Luzula sect. Luzula (Juncaceae) in the South-Eastern Alps: morphology, determination and geographic distribution

Bačič T., Dolenc Koce J. and Jogan N. 2007. Luzula sect. Luzula (Juncaceae) in the South-Eastern Alps: morphology, determination and geographic distribution. Bot. Helv. 117: 75 – 88.Within the genus Luzula, the type section (Luzula sect. Luzula) is particularly variable and taxonomically diverse. Eight taxa of Luzula sect. Luzula occur in the Alps. While these taxa have distinct caryotypes, their identification based on morphological traits has remained problematic, and their geographic distribution is insufficiently known. A morphometric study was performed on herbarium material from Slovenia and neighbouring regions to identify additional discriminative characters and to establish the distribution of taxa within the territory of Slovenia. We measured 52 plant traits on 233 herbarium sheets and analysed the data with multivariate statistical techniques. Results showed a clear differentiation between L. campestris and the seven other taxa, which were only discriminated by combinations of several quantitative characters. In general, ripe fruits are required for a reliable determination. Four of the eight taxa are widespread in Slovenia: L. campestris and L. divulgatiformis in the lowlands (mostly < 800 m), L. exspectata at higher altitude (> 900 m), and L. multiflora across a broad altitudinal range (200–1900 m). Two taxa (L. divulgata and L. alpina) proved to be rare in Slovenia, and two taxa (L. sudetica and L. pallescens), previously reported for the area, were not confirmed. Distribution maps are presented for the six Slovenian taxa, and a new determination key is proposed for the eight Alpine taxa.

Diversification of Luzula sect. Luzula (Juncaceae) on the Balkan Peninsula – a cytogenetic approach

Luzula sect. Luzula is one of the taxonomically most intricate groups of angiosperms, where diversification is mostly driven by true polyploidy and agmatoploidy (fission of chromosomes) leading to three different karyotypes (whole chromosomes – AL, half-sized chromosomes – BL and quarter-sized chromosomes – CL). Morphologically, the taxa are often difficult to distinguish, and genome size data coupled with karyological investigations are currently the most reliable means for their identification. For the Balkan Peninsula, one of the botanically least studied areas of Europe, ten taxa from this section have been reported, but little is known about their distribution. We here estimated the nuclear DNA amount (genome size, GS) using interphase-peak DNA image cytometry and counted the chromosomes for 33 populations of five species of Luzula sect. Luzula mostly from mountainous areas of the Balkan Peninsula and the adjacent southeastern Alps. Five taxa have been confirmed, of which L. divulgatiformis is new for Croatia and L. exspectata for Macedonia and Serbia. The most common species in the Dinaric mountains appears to be diploid (2n = 12 AL) L. taurica, for which the GS (2C = 0.83 pg DNA, fitting well in the range of previously determined values of diploid taxa) has been determined for the first time. The GS and karyotypes of other taxa (L. campestris, L. divulgatiformis, L. exspectata, L. multiflora subsp. multiflora) correspond well to previously published values. An identification key for the Balkan taxa of Luzula sect. Luzula is also included.