A key for the identification of conifer stomata from N.E. China based on fluorescence microscopy

• A regional key to species level for coniferous stomata identification from N.E. China has been established.
• Fluorescence technique has been applied for stomata observation in situ from modern and fossil coniferous leaves.
• Fluorescence technique has been applied for individual coniferous stomata observation from pollen slides.
• Different fluorescence excitation wavelengths have been tested.

Stomata analysis is an important tool for palaeoecological and palaeoenvironmental research. Coniferous stomata are lignified and similar in size to pollen grains. Detached from the epidermis, individual stomata can be preserved in Quaternary sediments and are often found in palynological preparations. Their identification is important for environmental and climatic interpretation. By using macrofossil remains of needle leaves and fresh needle leaves, in this study a regional identification key to the species level for coniferous stomata from Long Gang Volcanic Field (N.E. China, Jilin Province) is presented. For the microscopic investigations and the measurement of stomatal features, fluorescence techniques were applied. Three types of fluorescence filter sets using ultraviolet (UV), blue, and triple mixed excitation wavelengths were employed. To test the key and the fluorescence effect with fossil material, individual stomata from palynological slides were studied. Our results show that individual stomata have similar fluorescence to those in situ on macrofossil needles. For future stomata research, fluorescence microscopy using blue light excitation is strongly recommended.