New ethereal plant species do not use photosynthesis

Hidden by the shadows of enchanting Asian forests, strange growths can be seen between dead leaves like the ghosts of long-dead flowers.

The plant’s foliage lacks green pigment having abandoned photosynthesis in favor of an alternative source of nutrients on the forest floor, a source stolen from the fungi that many other plants consider friends – the symbiotic mycorrhizae that connect most forest plants into a wide canvas of wood.

Found widely across East and Southeast Asia, from the Himalayas to Japan, Monotropastrum humble it was thought to be a single species. Now researchers from Japan and Taiwan have discovered a pink hue that qualifies as a unique species in its own right, the one they named Monotropastrum kirishimense.

The wide webs of wood – incredible networks of fungi and plant roots that cover entire forests – act as highways for nutrient deliveries as well as wires to transfer information between plants via electrical and chemical signals. These connections help strengthen a forest as a whole, distributing resources from nutrient-poor areas to nutrient-rich areas of the network. They also allow plants to warn each other of predators and even protect them from drought.

In exchange for these services, plants pay their fungal allies some of the hydrocarbons they produce through photosynthesis.

But Monotropastrum betrays this mutualistic relationship by stealing all of its nutrients from the fungi, offering no photosynthetic products to the network in return – enrolling them in a highly selective mycoheterotrophic club.

Three photos of the new pink species and three of the known white species
The new species (top) and Mr. humiliated (background). (Suetsugu et al., J Plant Res2022).

The most distinct feature of the newly described Japanese variant is its blushing pink petals and sepals, but there are other differences as well, the researchers note.

Unlike their cousin Mr. humiliated, the roots of the newly discovered plant barely protrude from the ground. They are also more strongly associated with a Russula mycorrhizal lineage, while Mr. humiliated promotes a completely different variety of mushrooms.

Moreover, although they grow next to each other, from M. kirishimense the flowering season does not overlap with that of Mr. humiliated, flowering 40 days later than the better known species. This study of these life cycle and wildlife interactions with physical forces on earth such as the seasons is called phenology.

“Our multifaceted evidence leads us to conclude that this taxon is morphologically, phenologically, phylogenetically, and ecologically distinct, and should therefore be recognized as a separate species,” Kobe University ecologist Kenji Suetsugu and colleagues conclude in their article.

“Our study presents the exciting possibility that a host change in M. kirishimensetowards a certain Russula lineage, triggered ecological speciation.”

Their different flowering seasons ensure the main pollinator they share, the bumblebee Bombus diversuscannot accidentally give one species the pollen of the other, preventing hybridization.

Many of the world’s forests are under threat and, as Monotropastrum species depend on ancient forests, these strange plants are also vulnerable to extinction. M. kirishimense is rare and researchers suspect it is likely endangered.

The new factory was described in the Plant Research Journal.

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