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As children, we are taught what the functions of a leaf are photosynthesis (converting sunlight into chemical energy) and storing WaterThis is generally true, including salad We eat leaves.
However, the surface of a leaf is not just a gradient – it is a complex lattice of chemical compounds, which have different properties in different areas. By finding out where lettuce’s weaknesses are concentrated (in its hydrophilic or “water-loving” areas), we can find new ways to keep it safe, make it last longer, and make production and selling easier.
not so waterproof
To protect themselves, leaves and other aerial parts of plants, such as flowers, stems and fruits, are covered with a waxy, more or less waterproof layer made of fat (lipid), called cuticle. It is similar to a natural raincoat, although its composition and structure are not uniform.
But what if the leaves aren’t as waterproof as we thought? This would explain one of the great household mysteries: why lettuce wilts and spoils so quickly.
nano world of salad
If the cuticle is an impermeable layer of lipids, as has been believed for centuries, then how can water escape from the interior of the leaf?
To uncover this mystery, a multidisciplinary team of scientists peered into the “nanoworld” of the lettuce leaf, viewing the leaves at a level of detail a thousand times smaller than a human hair. Thanks to atomic force microscopy (AFM) and other advanced techniques, we discovered that the surface of plants is not a continuous, uniform layer of wax, but rather has chemical heterogeneity, or “patchiness”, at the micro and nano scales.
We’ve seen it on rose petals, olive leaves and now even lettuce. It is as if the leaf raincoat had some areas of fabric that repel water, and other areas that attract it.
We chose lettuce leaves for our study because they spoil quickly and absorb water easily.
We wanted to answer one question: Why is this leaf so perishable and vulnerable to microbial contamination? In other words, why does it go bad so quickly? Does its surface have low barrier properties to prevent dehydration and pathogen attack?
epidermal cells of lettuce
In our study – conducted by the Polytechnic University of Madrid, the University of Murcia and the University of Valencia – we analyzed in detail the surface of the upper and lower leaves of a variety of lettuce.
We chose romaine lettuce, a common, highly perishable vegetable. It quickly fades and deteriorates, and is very sensitive to microbial contamination. This suggests that its “raincoat” (cuticle) is not as effective a protective barrier as that of other plants.
The surface of the leaf is mainly made up of two types of cells. “Pavement” cells cover most of the surface, while “guard” cells are made up of two kidney-shaped cells that join together to form a pore called a stomata (from the Greek word). stomameaning “mouth”).
About the authors
Victoria Fernández is a researcher at the Polytechnic University of Madrid (UPM). Anna Kross Stotter, University Professor. Applied Physics, University of Valencia. Jaime Colchero, Full Professor. Solid State Physics, UNESCO Code 2211, University of Murcia.
This article was originally published by Conversation And it is republished under a Creative Commons license. read the original article,
The density of stomata is slightly higher on the lower side of the leaves. However, both sides are generally similar in structure and chemical composition.
The main role of stomata is to open to allow carbon dioxide to enter for photosynthesis, although they also allow water vapor to exit. Stomatal opening is well controlled at the plant level, but can be affected by a variety of stresses.
Analyzing the salad revealed something important. While pavement cells have a fairly homogeneous surface rich in water-repellent lipids, the guard cells that form the stomata are diverse. The surface of the stomata is chemically heterogeneous or diverse. Between the hydrophobic (water-repellent) regions there are also hydrophilic (water-friendly) regions.
Chemical diversity, and why it matters.
Our study shows for the first time that the surface of stomata, in addition to being rough, also exhibits chemical diversity.
The purpose of stomata is to open leaves for photosynthesis and to allow carbon dioxide to enter the leaves, thereby limiting water loss. However, we believe that the chemical diversity concentrated at the surface probably serves an additional function that we have yet to explore further.
We can speculate on possible effects, such as a relationship between the hydrophilic regions of a plant and its susceptibility to contamination by bacteria or viruses. These areas also promote water loss from inside the leaves. By losing more water, they spoil after harvest, including at the time of sale.
Similarly, it is possible that this asymmetric structure of the stomata limits carbon dioxide loss and the transport of hydrophobic substances, and this affects the mechanical properties of the leaf.
Lettuce is the first horticultural species to be studied in such detail. However, we believe that studying the surface of fruits and vegetables is essential to finding ways to extend and improve their shelf life and extend their life after harvest – all of which contributes to a stronger, more robust food supply.