Seed germination of mudflat species responds differently to prior exposure to hypoxic (flooded) environments

Mudflats are exposed for short periods after flood water drawdown. They support fast-growing annual herbs with a ruderal strategy. To optimize their recruitment success, seeds of mudflat species germinate better under fluctuating temperatures, full illumination and aerobic environments that indicate the presence of optimal (non-flooded) conditions for plant growth and development. Here, we hypothesize that prior exposure of mudflat seeds to hypoxic (flooded) environment interferes with the germination process and results in more vigorous germination once aerobic conditions are regained. To test this hypothesis, seeds of five mudflat species were incubated in both aerobic and hypoxic environments at four (14/6, 22/14, 22/22 and 30/22°C) temperature regimes, reflecting different (seasonal) conditions when drawdowns may occur. All species responded positively to four temperature regimes; however, moderate 22/14 and 22/22°C temperatures were optimum for high percentages and rates (speed) of seed germination. Since seeds of four species germinated exclusively under aerobic conditions, they were moved from hypoxic to aerobic conditions. Prior exposure of seeds to hypoxic environment facilitated high percentages, rates and synchronization of germination of Limosella aquatica, Peplis portula and Samolus valerandi seeds compared to incubation under strict aerobic conditions. However, prior exposure to hypoxic environment induced secondary dormancy in non-dormant seeds of Hypericum humifusum but broke dormancy in Lythrum hyssopifolia seeds that otherwise required cold stratification to overcome physiological dormancy. All species that have a narrow ecological niche (strictly occurring in mudflat habitats) showed positive responses to prior exposure to hypoxic environments. In contrast, H. humifusum that has a wide ecological niche (from mudflats to moist sandy grasslands) showed a negative response. We conclude that the hypoxic environment may strongly affect seed germination behaviour once the aerobic environment is regained. The most striking effect is the acceleration of the germination process and, therefore, life cycle supporting the survival in an ephemeral habitat.

Four new species (Trombidiformes: Eriophyoidea: Eriophyidae) and one new record of Aceria from arid and semi-arid areas in East Iran

During the field study of eriophyoid mites from autochthonous plants in semi-arid and arid environment in East Iran (Birjand, South Khorasan, from 2016 to 2017), four new Aceria species (Trombidiformes: Eriophyoidea: Eriophyidae) were collected. They are Aceria halothamni sp. nov. on Halothamnus auriculus (Moq.) Botsch. (Amaranthaceae), Aceria acanthophylli sp. nov. on Acanthophyllum sordidum Bunge ex Boiss. (Caryophyllaceae), Aceria samoli sp. nov. on Samolus valerandi L. (Primulaceae), Aceria aeluropi sp. nov. on Aeluropus littoralis (Gouan) Parl. (Poaceae). In addition, Aceria atriplicis Wilson & Oldfield, 1966 was also found on Atriplex leucoclada Boiss. (Amaranthaceae), which is a new record for Iran. All these species are illustrated and described herein. They appear to be vagrants and no symptom was observed on their infested plants.

Rare plant species of salt marshes of the Croatian coast

Between 2011 and 2016 we surveyed 42 sites of coastal salt marshes of Croatia. We confirmed the occurrence of several rare and endangered plant species. Ten of them are included in the Red List of Croatia; critically endangered (CR) Eleocharis uniglumis, Triglochin barrelieri and T. maritima, endangered (EN) Carex divisa and C. extensa, vulnerable (VU) Parapholis incurva, Salsola soda and Suaeda maritima and category data deficient (DD) Limonium virgatum and Puccinellia festuciformis. We also report localities of other rare taxa of salt marshes like Allium telmatum, Tripolium pannonicum subsp. tripolium, Juncus gerardii, Parapholis filiformis, Plantago cornuti, Samolus valerandi and Scorzonera parviflora. Several plant species are endangered. Their habitats, salt marshes were converted into fields or destructed by construction for developing tourist infrastructure. Today only a part of the remained areas are under protection.