No matter how much care we provide our crops, they will not always develop in optimal conditions. There are a number of factors that will affect them, causing stressful situations.
Like all living beings, plants are subject to the influence of climatic conditions and the incidence of other living organisms. These factors influencing plants cause stress situations that cause the plants' responses to vary from physical modifications to changes at the physiological and/or biochemical level, with the sole purpose of staying alive (Larcher, 1995).
We can define plant stress as any type of adverse situation that affects them both physiologically and biochemically, that is, the presence of a factor external to the plant exerts a negative influence on their optimal development. Although stress is a relative concept, since a given environmental situation may be stressful for one species but not for others.
Although it never ceases to amaze us how plants are able to adapt to changes in order to prosper, in the case of agriculture this effort by the plant will inevitably lead to a decrease in the quantity and quality of production.
And this stress will occur to a greater or lesser extent throughout our crop cycles, which is why our main objective is to minimize it.
We can divide plant stress factors into two classes:
Biotic factors: By the action of living beings.
- Large and small animals
- other plants
- Insects
- Bacteria, fungi and viruses
- Nematodes
Abiotic factors: Physicists and chemists.
- Drought (water stress)
- Excess salts in the soil (saline stress)
- Heat, cold and freezing (stress due to extreme temperatures)
- Luz
- Waterlogging and flooding (anaerobic stress)
- Stress from environmental pollutants (CFCs, ozone, herbicides, metals, etc.)
- Deficiency in mineral elements (nutritional stress) or Wind, compact soil… (mechanical stress)
- injuries or wounds
Faced with all these types of stress, the plant develops resistance mechanisms that help mitigate them. We can therefore define stress resistance as the ability of a plant to resist, avoid, and escape negative environmental stimuli or being able to remain under a particular state of stress without their phenotype being significantly modified.
Phenotypic manifestations of stress include deformations such as yellowing, stains, necrosis, etc. Other less obvious ones require special techniques for their detection, such as Low enzymatic assimilation, induction of gene transmission, changes in chemical composition, etc.
We have already seen that biotic factors, such as attacks by herbivorous insects, diseases caused by pathogenic fungi and bacteria, and viruses transmitted by vectors (nematodes, for example), produce stress conditions in the plant that will lead, if not to the death of the plant, at least to a decrease in productivity and/or quality.
These damage attributed to plant pathogens They are common in agricultural crops and worldwide, causing significant economic losses annually (Zamudio-Moreno et al., 2015).
Any infection in plant tissue begins when the pathogen enters the host. Depending on the nature of the pathogen, it is classified as (Glazebrook, 2005):
- Organism biotrophic, if they invade the plant through natural openings and do not cause cell death in their host, so they do not present obvious symptoms of infection in the short term.
- Organism necrotrophicIf they invade the plant through wounds or dead tissue, they kill the cells and feed on their remains, causing obvious necrotic symptoms in the short term.
- Organisms hemibiotrophic, if they combine both forms of invasion.
Worldwide, resistant cultivars developed through genetic improvement programs are used to reduce damage caused by plant pathogens (Kobayashi et al., 2014). To implement these programs, there are three sources of plant protection genes:
- Natural resistance genes.
- Pathogen-derived resistance.
- Resistance conferred by other sources, such as cross-protection, use of antibodies, post-transcriptional gene silencing or resistance mediated by biostimulation.
There is a vast body of research that indicates that plants refine and increase their defensive capacity against pathogens after a appropriate stimulus, and this resistance mechanism is regulated by a network of the signaling pathways of hormones salicylic acid (SA), acid jasmonic (AJ) and ethylene (ET) that induce the expression of distinct sets of genes (Gurunani, 2012). Interactions between signaling pathways are mediated by two forms of systemic resistance, Acquired Systemic Resistance (ASR, mediated by AS) and Induced Systemic Resistance (ISR, mediated by AJ and ET).
Some features in which you can differentiate RSA and RSI are that, in the case of RSA, it is induced by a wide number of biotic elicitors (among which are biotrophic and hemibiotrophic organisms) or abiotic, induces the production of PR proteins and uses signaling pathways that may involve AS. On the other hand, RSI is activated by biotic agents (including herbivorous insects and necrotrophic organisms), is potentiated by the plant-PGPR interaction, does not involve the synthesis of PR proteins and signaling is carried out through AJ and ET (Wang et al., 2009).
We are currently in the ongoing development of biofertilizers or whose end is to increase the resistance of crops to stress and to help them recover. Its purpose is to promote in plants the physiological mechanisms necessary to overcome these adversities, in addition to significantly increasing the systemic resistance against diseases and pathogens.
From the technical and R&D department of Cultifort, we want to talk to you about SPIRALIS Long Life y SPIRALIS ECO Long Life, the result of the development of an innovative line of R&D, the Natural Defensive BiotechnologyThese are fertilizer products, conventional and organic respectively, formulated together with a complex of selected organic acids and peptides, related to green and red algae, which facilitate their assimilation by the plant and enhance the effect bioprotector against various stress factors. The synthesized endogenous defensive molecules induce structural changes in cell walls of plants at the level of their lignification, thus constituting a physical barrier against stress. Its use is recommended every 15 days, in risk situations and in all types of crops, to prevent and overcome stress conditions.
