Biostimulants as a tool against heat stress in crops - AgriTecno sustainable solution

The debate on climate change is becoming more and more recurrent, a concern that has become evident with the temperature increases that have occurred over the last few years. On a global scale, we can observe temperatures reaching some of the highest values ever recorded in history. Global warming is the progressive increase in global temperature over time, caused by rising concentrations of greenhouse gases (Jarma et al., 2012). This is a global phenomenon with significant consequences and large-scale impacts that are difficult to predict with certainty. The concerns are the periods of high temperatures that have been occurring in different regions of the world, which have a clear impact on food production and the rising role of plant biostimulants (Jarma et al., 2012).

HOW DO HIGH TEMPERATURES AFFECT CROPS? 

There is scientific evidence on the impact of climate change on agriculture (IPCC, 2007). Temperature is a key factor influencing crop growth. Each crop has an optimum temperature range within which crops will grow well and a maximum temperature range beyond which irreversible crop damage occurs.

Heat stress is the increase in temperature beyond a threshold for a period of time sufficient to cause damage that hinders plant growth and development. Heat stress has serious consequences on crop yields and is attributed with large agricultural losses (Jha et al., 2014). 

Table 1. Maximum temperature threshold for some crops. Adapted from A. Wahid et al. (2007). Heat tolerance in plants: An overview

HOW DOES HEAT STRESS AFFECT PLANTS?

If temperatures rise above the maximum limit for a certain period of time, irreversible damage occurs at the cellular level, affecting crop growth, development and yield.

Some of the adaptive changes that occur in the plant under heat stress are:

ELECTROLYTE LEAKAGE

The cell membrane is the first to be affected by heat stress (Whang et al., 2011); high temperatures increase its fluidity and permeability, causing membrane lipids to become more fluid and permeable (Savchenko et al., 2022), and allowing electrolyte leakage (Los & Murata, 2004 ; Porch and Hall, 2013Gisbert-Mullor et al., 2021).

Electrolyte leakage can be used as a marker of heat tolerance such that heat stress tolerant plants show lower membrane permeability than non-tolerant plants (Chaves-Barrantes & Gutiérrez-Soto, 2017 ; Wang et al., 2011; Gisbert-Mullor et al., 2021).

HSPs 

The plant responds to heat stress by synthesising and accumulating heat shock proteins (HSPs) (Iba, 2002; Zinn et al., 2010). HSPs protect and repair proteins against heat damage (Barua et al., 2003; Wang et al., 2004; Hu et al., 2020), allowing cells to function during episodes of high temperature stress (Wahid et al., 2007; Chaves-Barrantes & Gutiérrez-Soto, 2017).  

ANTIOXIDANT PRODUCTION

Heat stress causes oxidative stress by inducing the production of reactive oxygen species (ROS). To attenuate the damage caused by ROS, plants produce a number of antioxidant enzymes (Almeselmani et al., 2006; Wahid et al., 2007).

COMPATIBLE OSMOLYTE ACCUMULATION

Under high temperature stress, plants accumulate compatible osmolytes (Schwacke et al., 1999; Iba, 2002; Nagesh & Devaraj, 2008; Chaves-Barrantes & Gutiérrez-Soto, 2017). The accumulation of these solutes gives the plant increased tolerance to heat stress (Park et al., 2006; Wahid, 2007; Wahid & Close, 2007; Chaves-Barrantes & Gutiérrez-Soto, 2017).

Role of plant biostimulants in mitigating the effects of climate change on crop performance

At Agritecno we are very aware of the damage that climate change causes and will cause on crops and that is why, from our R&D department, we are researching in obtaining biostimulant products that increase the resistance of plants against heat stress. We have carried out transcriptomic tests that have allowed us to select the best active compounds capable of improving plant tolerance to heat stress.

Tabla 2.  Genes activated by an exclusive Agritecno raw material in stress situations. The extract induces the expression of heat shock proteins and enzymes involved in neutralising Reactive Oxygen Species (ROS) released during the stress period.

Ongoing research in this area has led us to continue searching for formulations based on active compounds capable of improving plant tolerance to stress. For this reason, another test in a growth chamber has allowed us to obtain data that demonstrate the effectiveness of our treatments in heat stress situations. In the following study carried out in a growth chamber, tomato plants were subjected to temperatures of 40℃ day and 28℃ night for a period of 7 days. Two treatments were carried out with Agritecno formulations at a dose of 3L/ha (Table 3). 

Table 3. Heat stress test conditions.

The results showed that with the addition of our product we improved the Leaf Area Index of the plants by 67%, the dry weight of the leaves by 33% and the height of the plants by 39%; we also stimulated root development by increasing the Root Area Index by 30% and the dry weight of the roots by 10%. The plants treated with the Agritecno product managed to increase their vegetative and root development compared to control plants subjected to the same heat stress conditions.

The preliminary results of these trials have shown us that the formulations selected on the basis of our knowledge of active compounds stimulate plant development and help them to better withstand the adverse conditions caused by heat stress. 

These first data are good results that encourage us to continue our research in order to obtain products specifically formulated to meet the present and future needs of the agri-food sector.

Contact

contact-us@agritecno.es

aijia.zhang@agro2agri.com

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