Pollinators are not just attracted to plants by scent, but also by humidity • Earth.com
The significance of humidity in luring pollinators to plants has emerged as a potent factor in a recent research led by Cornell University
05-20-2023

Pollinators are not just attracted to plants by scent, but also by humidity

The significance of humidity in luring pollinators to plants has emerged as a potent factor in a recent research led by Cornell University. This newfound information, a breakthrough in basic biology, has potential to revolutionize agricultural practices.

The study, published in the journal Current Biology, was a collaborative endeavor involving scientists from Cornell, Harvard University, and the Montgomery Botanical Center. 

The researchers explored the behavior of the weevil, a pollinator for the plant Zamia furfuracea. The team’s findings revealed that the weevil’s sensitivity to humidity is on par with its response to scent.

New insights discovered into how plants and insects interact

Shayla Salzman, the first author of the study, remarked on this breakthrough in the understanding of plant-insect interactions. 

Salzman, a postdoctoral National Science Foundation fellow in the School of Integrative Plant Science Plant Biology Section at Cornell, stated: “The world of plant-insect interactions was drastically changed by the work that was done on visual and scent cues.” 

“We’re just starting to realize how many other factors are playing a role in plant reproduction and impacting insect decision making, pollination and success.”

Humidity had previously been considered a byproduct

Co-author and PhD candidate Ajinkya Dahake led an earlier study, published in Nature Communications, that identified humidity as a signal encouraging hawkmoths to pollinate the sacred datura flower (Datura wrightii). These combined studies underline the active use of humidity by two vastly distinct plants to encourage pollination.

“Prior to our research, humidity was seen as just an outcome of evaporation of nectar, a side note. What we’ve found is that this is an active process of the flower, coming through specialized cells, and these organisms may even have evolved to privilege this humidity release, because it attracts pollinators,” explained Dahake. 

Previously, research into plant-insect interactions and pollination largely targeted visual and scent cues – markers that humans can also perceive. However, insects are significantly more proficient than humans at detecting changes in factors like humidity, carbon dioxide, and temperature, according to Salzman.

Still much more to learn

In light of the ongoing climate crisis, which is directly affecting these elements, Salzman said, “It’s crucial that we understand how insects utilize all of that information in their interactions with plants.” 

This information could potentially assist farmers and food distributors to encourage pollination of crops, or to direct insects away from stored foods towards traps.

Dahake explained that while humans require substantial changes in humidity to notice a difference, insects can detect minute changes. 

“Insects have specialized receptors that respond to very small changes in humidity: Even a change of 0.2% to 0.3% will cause a neuron to fire,” said Dahake. “Even a one part per million change in carbon dioxide concentration will cause an insect neuron response.” 

The implication of these findings on insect behavior is still a matter of ongoing research.

More about pollination

Pollination is a crucial biological process for the reproduction of most flowering plants, including many crops that make up a significant proportion of our diet. It is essentially the transfer of pollen from the male parts of a flower (the stamens) to the female part (the pistil) of the same species. This process allows fertilization and the production of seeds, ensuring that a new generation of plants can be born.

Types of Pollination: 

Pollination occurs in two main types:

Self-Pollination

In self-pollination, pollen grains are transferred from the stamen to the pistil of the same flower or another flower on the same plant. This method of pollination doesn’t promote genetic diversity but guarantees reproduction in isolated areas or harsh conditions where cross-pollination may not be possible.

Cross-Pollination

This process involves the transfer of pollen from the stamen of one flower to the pistil of another flower on a different plant of the same species. Cross-pollination encourages genetic diversity, leading to stronger, more resilient plant populations.

Mechanisms of Pollination: 

Animal Pollination

Many plants rely on animals, such as bees, butterflies, bats, and birds, to carry their pollen to other plants. The animals are usually attracted by the plant’s colorful petals, scent, or the promise of nectar. As they feed, pollen sticks to their bodies and is transported to the next flower they visit. Some plants have evolved alongside specific pollinators, leading to unique floral adaptations that make it easier for these pollinators to access their nectar and pollen.

Wind Pollination

Some plants rely on the wind to carry their pollen to other plants. These plants usually have small, inconspicuous flowers and produce large quantities of lightweight pollen. Common examples include grasses, corn, wheat, and many trees.

Water Pollination

Although less common, some plants use water as a medium to transfer pollen. This mechanism is primarily seen in aquatic plants.

Importance of Pollination:

Pollination is crucial to the food supply. According to the Food and Agricultural Organization (FAO), more than 75 percent of the world’s food crops rely to some extent on animal pollination. Additionally, pollinators contribute to crop quality, increasing the market value of many agricultural products.

Pollination is also vital for maintaining biodiversity in natural ecosystems. The mutualistic relationships between plants and their pollinators have led to the evolution of diverse species and complex ecosystems.

However, pollinators worldwide are under threat due to habitat loss, pesticide exposure, climate change, and disease. The decline in pollinator populations poses a serious risk to global food security and biodiversity. Efforts are underway to protect and conserve pollinator species to ensure the sustainability of our food supply and the health of our ecosystems.

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