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Cells, Genes & Molecules

Plants many plants need insects to pollinate their flowers for reproduction, and they use pigments in many colours to entice visitors. But there’s always room for improvement, and some plants go beyond pigments to engineer the surfaces of their petals to add new colours. Edwige Moyroud and colleagues have looked at the striations on the surface of some petals that can make them iridescent.

Two flowers, but the one on the left has a shimmering purple-blue centre. A close up microscope image of the petal shows ridges in parallel on the surface of the blue petal, but a much smoother surface on the other petal.
There is a clear visible difference between striated and smooth petal surfaces when the petals are viewed under microscopes: Hibiscus trionum (left) has microscopic ridges on its petal surface that act as diffraction gratings to reflect light, while Hibiscus sabdariffa (right) has a smooth surface. Image: Edwige Moyroud.

“Our initial model predicted that how much cells grow and how much cuticle those cells make were key factors controlling the formation of striations,” said Dr Moyroud, “but when we started to test the model using experimental work in Venice mallow we found out that their formation is also highly dependent on cuticle chemistry, which affects how the cuticle responds to the forces that cause buckling.”

Dr Moyroud added: “Plants are formidable chemists and these results illustrate how they can precisely tune the chemistry of their cuticle to produce different textures across their petals. Patterns formed at the microscopic scale can fulfil a range of functions, from communication with pollinators to defence against herbivores or pathogens. They are striking examples of evolutionary diversification and by combining experiments and computational modelling we are starting to understand a little bit better how plants can fabricate them.”

📰 Press release at Eurekalert.
🔬 Cuticle chemistry drives the development of diffraction gratings on the surface of Hibiscus trionum petals at Current Biology.

Growth & Development

If you’re a fan of corn on the cob in the US, then you’re likely to have to dig deeper into your pockets to pay for it. Research in Scientific Reports shows that Zea mays yields drop dramatically when temperatures exceed 30°C during flowering. The US Global Change Research Program predicts 20 to 30 more days over 32 C [about 90 F] by mid-century across much of the U.S.

“The reality is that producing sweet corn, one of the most popular vegetable crops in the U.S., will be more difficult in the future. We need to develop new approaches and technologies to help crops adapt to climate change,” says Daljeet Dhaliwal, former graduate research assistant and lead author on the study.

“Our analysis reveals that small temperature changes have a greater influence on crop yield compared to small precipitation changes for both rainfed and irrigated fields in the Midwest and Northwest, but rainfed production shows greater sensitivities,” co-author Martin Williams says.

“If there’s a bad time for extreme heat, it’s during flowering. That’s especially true in a crop where ear quality is so important. With heat stress during flowering, you can have ears with fewer kernels or very misshapen kernels that look nothing like what the consumer is expecting.”

Our analysis, using the whole distribution of growing season temperatures, showed that temperatures ranging from 8 to 30 ∘C∘C represent ‘benign’ growing conditions for sweet corn. Previous empirical studies conducted under controlled environmental conditions have determined the same range of temperatures beneficial for field corn growth and development… This is worrisome as the recent trends toward colder, wetter Midwest spring weather often results in delayed spring planting, thereby exposing the crop to hot summer weather for a longer duration.

Dhaliwal & Williams 2022.

📰 Press Release at Eurekalert.
🔬 Research: Evidence of sweet corn yield losses from rising temperatures at Scientific Reports.

Cells, Genes & Molecules

Animals can adapt quickly to survive adverse environmental conditions. Evidence is mounting to show that plants can, too. A paper in the journal Trends in Plant Science details how plants are rapidly adapting to the adverse effects of climate change, and how they are passing down these adaptations to their offspring.

Plants are facing more environmental stressors than ever. For example, climate change is making winters shorter and less severe in many locations, and plants are responding. “Many plants require a minimum period of cold in order to set up their environmental clock to define their flowering time,” says Martinelli. “As cold seasons shorten, plants have adapted to require less period of cold to delay flowering. These mechanisms allow plants to avoid flowering in periods where they have less chances to reproduce.”

Animals use neurons to create memories, but plants like neurons and so need another method to remember.

Plants possess a somatic memory that can last for some time during the life of an individual plant, and is maintained through mitosis…, but there is also increasing evidence of long-lasting memories with information transmitted to one or more subsequent generations… In this context, epigenetic mechanisms have drawn attention because they can mediate the learncing, storage, and transmission of information without modification in the DNA sequences… As such, these modifications, which constitute an epigenetic alphabet, orchestrate the response of plants to their environment and are essential actors in the priming phenomenon. Epigenetic modifications are also key elements of the molecular mechanisms underlying plant memory, as well as of the ability of plants to forget, and therefore appear as an essential component of plant intelligence.

Gallusci et al. 2022.

The authors add in their paper that epigenetics also allows plants to transmit their experiences to their offspring. However this isn’t all good news, there may be a cost to balance the benefit. The team conclude: “Although the phenomenon of transgenerational stress memory protects offspring against the previously occurred stress, it is also likely that inter/transgenerational-induced resistance is associated with an increased susceptibility to other stresses.”

A plant next to a clock that would be running backwards, symbolising memory - if this image were animated

📰 Press Release at Eurekalert.
🔬 Read Deep inside the epigenetic memories of stressed plants at Trends in Plant Science.

Growth & Development

As any gardener can tell you, root sprouting species are a pain to get rid of, as they can regenerate from even small root fragments. So why don’t more plants do this? Jana Martínková and colleagues took pairs of plants from the same genus with different root sprouting abilities and put them through a series of tests to see how they grew back.

The difference between root sprouting and non root sprouting plants.

We found differences in growth and acquisition strategies and carbohydrate concentrations between root-sprouting and non-root-sprouting herbs. These differences suggest that [root sprouting] species are better prepared for severe biomass removal, although this advantage was not fully manifested by regenerated aboveground biomass in our experimental plants. Based on our findings, root spouting ability presumably represents a valuable strategy under disturbance, although it seems that only more severe disturbance that removes all axillary buds would unequivocally favour [root sprouting].

Martínková et al. 2022.

The team found that root sprouting required a low auxin-to-cytokinin ratio, two hormones plant use to regulate development. However, balancing the two is important and plants that have too low a auxin-to-cytokinin ratio risk developmental deformities. So it’s the plants prepared for the greatest disturbances that will invest in root sprouting.

Read Why is Root Sprouting Not More Common Among Plants? Phytohormonal Clues and Ecological Correlates by Martínková et al. at Environmental and Experimental Botany

Cells, Genes & Molecules
Dr. habil. Krzysztof Jaworski, NCU professor from the Chair of Physiology of Plants and Biotechnology of the Faculty of Biological and Veterinary Sciences of the University in Toruń and Mateusz Kwiatkowski, M.Sc. Photo credit Andrzej Romański

When humans get hurt, they feel pain, but that pain signal passes through a chain of relay reactions. A similar thing happens to plants.  When a stimulus appears, for instance a pathogen attack, a plant receives this information through a receptor, analyses it, sometimes amplifies it and forms a corresponding reaction. 

“[A] plant hormone auxin, the major intracellular regulator of plant growth and development, is like a finger which pushes domino blocks.  The first block is the receptor, the activation of which moves other blocks.  At the end of this chain is a little ball, the final factor, which changes the expression of a defined set of genes, either inhibiting or activating the formation of proteins which affect the final physiological response of the organism,” says Dr. Krzysztof Jaworski.

Tests on plants as diverse as Arabidopsis and moss show that this is likely to be a common system for all plants.

The current model of canonical auxin signalling relies on TIR1/AFB auxin receptors acting as F-box proteins, which form a functional SCF-type E3 ubiquitin ligase together with other subunits… Here we show that TIR1/AFB receptors have an additional, AC activity that requires the AC motif in the C-terminal region of the protein… Given that TIR1/AFB receptors from both Arabidopsis and moss demonstrate similar AC activity, it is likely that TIR1/AFB receptors across all land plants share this activity.

Qi et al. 2022.

📰 Press Release: Eurekalert
🔬 Research: Adenylate cyclase activity of TIR1/AFB auxin receptors in plants @ Nature.
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Plants & People

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