The biological role of lipids in the vital activity and stress resistance of crops

Lipids are not just fat reserves of a plant, but a critically important factor in its viability, determining cell strength and the resistance of crops to stress. Physiologically, they are divided into storage (triglycerides) and structural (all other types). For an agronomist, understanding their role helps to assess how plants expend energy at the start of the growing season and how they withstand adverse conditions in the field.

• Energy released by the oxidation of 1 g of fat — 39 kJ
• Thickness of the membrane lipid bilayer — 3.5–4 nm
• Carbohydrate content in the membrane — 0.5–10 %
• Share of lipids in membranes — from 1/4 to 4/5

Membrane structure, substance transport, and stress protection

Structural lipids, together with proteins, form the basis of cell membranes and subcellular organelles: the nucleus, mitochondria, Golgi apparatus, and endoplasmic reticulum. In biomembranes, lipids are arranged in a double layer where the hydrophobic "tails" of the molecules face each other, while the polar hydrophilic heads are oriented outward. The ratio of components in membranes varies from 1/5 protein and 4/5 lipids to 3/4 protein and 1/4 lipids, and carbohydrates in the form of glycoproteins and glycolipids make up from 0.5 to 10 %.

The lipid bilayer does not simply separate environments, but also regulates the selective transport of substances into the cell and its compartments. Water, certain organic ions, and lipid-like compounds penetrate through pores in the lipid layer or through protein channels. The activity of bound enzymes and the course of oxidative phosphorylation — the process of ADP phosphorylation to form ATP, coupled with the transfer of electrons from reduced coenzymes to atmospheric oxygen — depend on the composition and properties of membrane lipids. In these reactions, lipids act as a "solid-state cofactor," providing an ordered hydrophobic environment.

The protective function of lipids directly affects harvest preservation during adverse weather. The lipids of the epidermal cuticle layer control water balance, preventing external waterlogging of tissues and curbing excessive moisture evaporation during droughts. The wax coating on leaves and fruits performs two key tasks:

• blocks the penetration of pathogenic microorganisms into plant tissues;
• mitigates the negative impact of high and low ambient temperatures due to the low thermal conductivity of lipids.

The regulatory function of lipids is expressed in their participation in metabolism management. Many of them serve as precursors for phytohormones and vitamins. In addition, lipids are part of plastid pigments, directly influencing the intensity and overall productivity of photosynthesis.