Stoller Academy Blog
Plant Health and Defense Mechanisms

The United Nations has declared 2020 International Year of Plant Health (IYPH) and Stoller, as a company committed to knowledge and research, joins the event that aims to raise awareness about a problem of international scale. Plant health protection can help end hunger, reduce poverty, protect the environment and stimulate economic development. FAO estimates that agricultural production should increase by 60% by 2050 in order to feed a larger and generally richer population. However, plant’s face a wide range of different stresses during their development, that can reduce and limit their productivity.

During plant development, plants are subjected to a wide range of stresses, these environmental stresses can be either of abiotic or biotic nature. Abiotic stress causes losses in all major crop plants worldwide and includes environmental factors like, extreme temperatures, flooding, droughts etc. On the other hand, attacks by pathogens such as fungi, bacteria, virus among others are known as biotic stresses. Currently plants face a combination of both types of stresses, where abiotic stresses like low temperatures and salinity are known to help spread pathogens and insects.

 

Plant Stress

 

Given that plants are sessile organisms, they face these stresses daily and have devised mechanisms to tolerate and even reduce the effects of these environmental conditions. They sense the external stress, get primed and thus produce physiological responses to confront the stress.

Plants are able to defend themselves from predators by synthesizing chemical attractants as a response of a stimuli produced from being attacked. Once the signal is produced, natural predators of the herbivores are attracted to the plant thus effectively reducing the attack from the original predator. These natural chemical messages are called VOCs (Volatile Organic Compounds), these compounds not only function to attract natural predators but are also involved in other types of defense mechanisms, such as S.A.R (Systemic Acquired Resistance).

 

Chemical Attractants

 

S.A.R is a defense mechanism by which the plant defends itself by priming a systemic response for producing defense molecules in both affected and healthy tissues after an attack by an external pathogen like bacteria or fungi.

 

Systemic acquired resistance

 

When a pathogen attacks a healthy tissue, such as a leaf, plants produce a series of proteins and accumulate a plant hormone called salicylic acid (SA), both of which result in a cascade of chemical reactions resulting in different defense gene expression, eventually ending in the synthesis of defense molecules that include pathogen related proteins (PR proteins).

 

These molecules work on a systemic level, thus priming healthy tissues and even producing VOCs that are airborne and travel to nearby plants sending them a message to prepare themselves for an attack. By these means, plants are able to stop the expansion of diseases within themselves, effectively reducing the damage that diseases cause on their development and productivity.

 

On the other end of the defense spectrum, another type of defense mechanism is the ISR (Induced Systemic Resistance), in this case beneficial microbes can cause an induced response within the plant, dependent on the action of two hormones: Jasmonate (JA) and Ethylene (ET).

 

Induced Resistance

 

Through ISR and SAR, plants can affect pathogens that are sensitive to either SA or JA/ET pathways, therefore effectively affecting a wide range of pathogens (Virus, bacteria, fungi etc.). Another interesting fact is that these defense mechanisms are not species specific, meaning that they are effective in different plant species, including those of great agronomical importance (potatoes, fruit trees, citrus, rice, vegetables, etc).

 

Helping increase these natural defense mechanisms in plants can improve their resistance to pathogen attacks, thus effectively reducing damages on crop productivity, moving one step further towards a future where global food security is key.

 

Abbas Caballero
Poduct Manager
Stoller Europe

 

References

Food and Agriculture Organization of the United Nations. 2020. Take Action!. [online] Available at: <http://www.fao.org/plant-health-2020/take-action/en/> [Accessed 10 March 2020].

Gull, A., Ahmad Lone, A. and Ul Islam Wani, N., 2019. Biotic and Abiotic Stresses in Plants. Abiotic and Biotic Stress in Plants,.

Pandey, P., Irulappan, V., Bagavathiannan, M. and Senthil-Kumar, M., 2017. Impact of Combined Abiotic and Biotic Stresses on Plant Growth and Avenues for Crop Improvement by Exploiting Physio-morphological Traits. Frontiers in Plant Science, 8.

Vallad, G. and Goodman, R., 2004. Systemic Acquired Resistance and Induced Systemic Resistance in Conventional Agriculture. Crop Science, 44(6), pp.1920-1934.

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