Investigating Mineral Distribution in Plant Trichomes with EDS

The elemental mapping of Echium hypertropicum, a flowering plant endemic to Cape Verde, was successfully carried out on a fresh sample with a scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The challenges of the sample sensitivity to the electron beam and shadowing effect of an irregular surface were successfully overcome using the innovative XFlash^® FlatQUAD detector at low acceleration voltage complemented with a Peltier cooling stage that brings the sample down to minus 50 degrees Celsius. 

Echium hypertropicum has epidermal outgrowths named “trichomes” on the upper surface of its leaves. Unlike the stinging trichomes found in species such as nettles, the trichomes of E. hypertropicum are non-threatening and serve protective and light-reflecting functions. Primarily, the mineralized trichomes hairs act as a shield, guarding against sun damage. By reflecting sunlight, trichomes prevent harm to the underlying leaf tissue. For this reason, trichomes are often present on plant species found in environments with high sunlight exposure such as mountainous regions. 

In E. hypertropicum trichomes exhibit a fascinatingly complex mineral distribution. Different minerals serve different structural and/or physiological functions. For example, the concentration of potassium observed around the stomata, a pore-like structure that surrounds trichomes, regulates their opening and closing. 

The intricate relationship between the plant's physiology and mineral distribution highlights the sophisticated mechanisms within E. hypertropicum. By understanding how plants regulate mineralization and ion concentration, researchers can gain valuable insights into the physiological processes underlying plant growth and adaptation to their environment.

The XFlash^® FlatQUAD detector facilitated the detailed elemental analysis and imaging of the trichomes and stomata of the fresh plant sample, overcoming inherent challenges such as the sample’s beam sensitivity and shadowing effects.