Rare Earths Have a Green Thumb

Postdoctoral scholar from MIT, Giorgio Rizzo, published a research paper this July exploring the usefulness of lanthanides (Lns) in preserving crops from UV light stressors while contributing as much benefit as possible. The findings would support that a mixture of (La 3+) Lanthanum III cation and a certain sugar called Trehalose, a common disaccharide produced by plants under stress, can improve the absorption and overall beneficial effectiveness of the Lns to promote fertilization of seeds, crop resilience against UV light, and even photosynthetic ability. These findings could prove a boon to the farmers around the world, improving the bounty of their harvest and minimizing loss of their produce.

Lanthanides are heavy metals that are peculiar due to both their surprising use cases in optoelectrical situations and their ability to aid in radio imaging. The human body can safely consume 1-2 milligrams of these heavy metals per kilogram of body mass, with some wide variation based on which Lns is considered. Gadolinium is widely used in medicine as a magnetic resonance imaging contrast while lanthanum carbonate is used  in medicines to control phosphate levels in people who need dialysis. These metals are not your typical heavy metals like lead, cadmium, and others. In fact, the metal is being studied for its anti-cancer effects. The Lns are used as a micronutrient in crop fertilizers in several countries already.

Countries like China, Korea, Japan, Australia, and Switzerland utilize these rare earth metals in their fertilizers. China alone uses them on around four million hectares of land. Although it is known that lanthanides play an essential cofactor role in certain enzymes of Methyllobacteria, which contribute to plant growth and resilience, it is still unknown what impact such elements have on the rhizosphere when used widely in agriculture. Rizzo’s study hopes to contribute a basis of foundational knowledge on the impact of (Ln 3+) Lanthanum III cations, those which exist as mobile and soluble ions in this oxidation state in the soil, on plant tissues.

Chlorophyll is corrupted into pheophytins when it is hit with too much ultraviolet light from the sun. It is known that these corrupted forms of the important chemical may be restored through a process called regreening when they are combined with the lower oxide isotopes of metals such as iron, copper, nickel and platinum. A gap in human knowledge has so far existed concerning the interaction between higher oxidation state lanthanides and chlorophylls, and there is no experimental data to show what effect these compounds have on photosynthesis.

Chlorophyll is well known to be a key player in photosynthesis, whereby plants synthesize sugar from carbon dioxide, water and sunlight. Have you ever heard that there are different kinds of chlorophyll? While most plants have more chlorophyll A than B, plants more suited to low-light environments are expected to have more chlorophyll B than A. The difference lies in the metabolic processes of the different kinds of plants. However, the ratio of A to B in the same plant over time is a useful indicator of plant stress.

To study the effect of these heavy-metal chlorophyll compounds called Me3+ complexes, scientists attempted to isolate both chemicals and combine them in vitro. The synthesis of crystalline chlorophyll proved problematic. ‘An analog derivative of chlorophyll called trisodium copper chlorophyllin (TCC) was used as a reference compound for chl.’ (Rizzo)

Results of an in vitro experimental study showed that the TCC preferred to bond with magnesium +2 ions over the lanthanides. When the chlorophylls combine with the Lns, they adopt a somewhat deformed, bent shape as well as electronic rearrangements. Despite these findings, the in vivo tests showed that amounts of Lns could be found in the leaves of 18-day-old plants after a nano-dose was administered on chickpea, corn, soybean, and barley seeds.

Experimental data showed that a micro-dose of 10 nanograms of a combination of Lns and Trehalose, administered to a seedling, was most beneficial for preserving the size, shape and color of the mature plant’s leaves exposed to ultraviolet light and heat. These findings show that a simple, minor chemical adjustment to biological matter, informed by cutting-edge research, can lead to great things. Farmers may be expecting higher crop yields and fewer losses in the future, and fewer people will go hungry.