Seed morphology and anatomy of the New Zealand genera Cheesemania, Ischnocarpus, Iti, Notothlaspi, and Pachycladon (Brassicaceae)

Abstract

Seed morphology, testa anatomy, and embryos of most New Zealand species of Cheesemania, Ischnocarpus, Iti, Notothlaspi, and Pachycladon (the last four genera endemic) are described and a generic key is provided. Seeds of Ischnocarpus and Pachycladon (Sisymbrieae) have a reticulate testa, thin-walled epidermis and palisade cells, large mucilage bodies, and a well-defined aleurone layer. Their embryos have incumbent radicles. I do not infer a close relationship between them as all these features are common elsewhere in the family. Seeds of Iti are similar but have a bireticulate testa and flat mucilage bodies. Seeds of Cheesemania (Arabideae) are also similar, but distinctively winged. They have smaller mucilage bodies, and their embryos usually have accumbent, but may have obliquely accumbent, or incumbent radicles.

Notothlaspi (Lepidieae) has distinctive seeds with a very large hilum, bireticulate testa with massive thickening of palisade cell walls, and primary areoles with sinuate margins. Mucilage bodies are apparently absent The very long incumbent radicle is twice folded, perhaps an adaptation to rapid establishment in its scree habitat.

Taxonomic conclusions must await similar comparative studies in Australia and South America.

Keywords:

• Brassicaceae
• seeds
• Cheesemania
• Ischnocarpus
• Iti
• Notothlaspi
• Pachycladon;
• morphology
• anatomy
• New Zealand