February 20, 2020 | David F. Coppedge

Smarty Plants

There’s more going on in your local weed than scientists could have imagined in Linnaeus’s day.

Carolus Linnaeus was a creationist who admired plants tremendously. It drove him to explore and classify plants from around the world. Had he known some of the things discovered recently, he might have stood up and shouted “Glory to God!”

How plant cells sense the outside world through hydrogen peroxide (Nature News). Hydrogen peroxide: H2O2 – what does that common household product bring to mind? Bleaching hair? Cleaning teeth? Plant signaling? Probably not the latter. But actually, this highly reactive oxygen species (ROS) is used by plants as a way to sense the outside world. Because of its chemical activity, it must be handled gingerly by plants. They store hydrogen peroxide outside the cell membrane, in a space called the apoplast between the membrane and the cell wall. This extracellular H2O2, labeled eH2O2, has a number of important roles, the article explains, that are fulfilled with the aid of complex molecular machines.

The apoplast and cell wall act as a dynamic interface between plant cells and the outside world, with all its threats, challenges and opportunities. Some eH2O2 moves from the apoplast into the cytoplasm through channel proteins called aquaporins. However, unlike the cytoplasm, the apoplast contains relatively few molecules that counteract oxidation — and so ROS, including H2O2, can survive for much longer in the apoplast than in the cytoplasm. This is a compelling reason to suspect that there is a sensor for eH2O2 in the apoplast.

Although little is known about the initial target of eH2O2, the consequences of its production are much better defined. It is clear that eH2O2 triggers an influx of calcium ions (Ca2+) into the cell, which then leads to the systemic transmission of signals between cells in waves, activating processes such as pathogen resistance or acclimation to stress across the entire plant. In addition, eH2O2 signals regulate the polarized growth of pollen tubes and root hairs, and control the opening and closing of stomata — pores on the outer layer of the leaf formed by two guard cells. Stomata enable the free passage of molecules such as carbon dioxide and oxygen into the plant when open, and can close to prevent water loss from the plant.

The eH2O2 sensor has now been found, the article goes on to say. Its name is HPCA1. This signalling molecule, anchored at one end into the cell membrane, undergoes a conformational change when hydrogen peroxide is around. It triggers the influx of doubly-ionized calcium Ca2+ through specialized calcium channels. This well-known signaling ion is responsible for triggering many kinds of responses in both plants and animals.

In this evolution-free article, writer Christine H. Foyer has described calcium channels, aquaporins, stomata with their guard cells, and now HPCA1 all working together to give plants a way to sense their outside world. The weeds at our feet never looked so talented.

Plants surround us, but there is so much to learn about their benefits.


Plant protein helps control powerhouse of plant cell (Phys.org). The previous article mentioned hydrogen peroxide as a dangerous molecule. This article tells how another protein named PRXQ helps protect the chloroplasts from peroxides, and thereby protect the light-harvesting powerhouse of plants. PRXQ can concert peroxide into less dangerous molecules. “Limiting this damage is a constant battle in plants, especially under stress conditions,” one scientist notes; and PRXQ is on duty 24 x 7.

Plants for Health

Striking essential oil: tapping into a largely unexplored source for drug discovery (Nature Scientific Reports). “Essential oils” are complex volatile compounds produced by plants. For centuries, people have used them for cosmetics and flavors in various products, as well as for home remedies and alternative medicines that scientists have generally dismissed. Some familiar examples are eucalyptus, turpentine, sage, tea tree and curcumin, but there are hundreds more.

Now, this article says that essential oils (EO) are a largely untapped resource for legitimate drugs. Who knows what cures are waiting to be found in these compounds? Why construct chemicals artificially when treatments may be under our noses in the garden? Scientists need to shove aside their biases and take a new look at essential oils:

EO components occupy a special niche in chemical space, that offers unique opportunities based on their unusual physicochemical properties, because they are typically volatile and hydrophobic. Here we evaluate selected physicochemical parameters, used in conventional drug discovery, of EO components present in a range of commercially available EOs. We show that, contrary to generally held belief, most EO components meet current-day requirements of medicinal chemistry for good drug candidates. Moreover, they also offer attractive opportunities for lead optimization or even fragment-based drug discovery. Because their therapeutic potential is still under-scrutinized, we propose that this be explored more vigorously with present-day methods.

Self-Healing Landscapes

Hurricanes fertilize mangrove forests in the Gulf of Mexico (Florida Everglades, USA) (PNAS). This paper may provide little consolation for those who have suffered a hurricane, and nobody would wish more of them upon the gulf states. There is a bright side, however, to consider. Florida’s Everglades have survived many a century despite being pounded almost every year by devastating storms. One reason is the mangrove: a unique tree that roots itself in salt water along sandy coastlines. Mangrove forests have developed an almost ‘symbiotic’ relationship with hurricanes.

Despite the destructive effect of hurricanes on mangrove forests in tropical and subtropical latitudes, hurricanes are major drivers controlling soil fertility gradients in the Florida Everglades mangroves, and therefore represent a positive influence in maintaining observed mangrove spatial distribution and productivity patterns. Hurricane-induced mineral inputs to near-coast mangroves in the Everglades enhance phosphorus (P) concentrations in soils, increase plant P uptake, promote soil elevation gains relative to sea level, and facilitate rapid forest recovery following disturbance. The response of mangroves to large-scale P fertilization from hurricanes may be an important adaptation of neotropical mangroves in the Gulf of Mexico and the Caribbean region to withstand the impacts of both sea-level rise and P limitation.

The storms fertilize the trees and bring in nutrients, and the trees protect the coastlines from much of the damage. How about that!

You can tell that intelligent design is a fertile inference when you keep finding more instances of it the closer you look.

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