By agrimag
By Bert Campomanes and Catherine Anne Porter
Water availability is a major limiting factor for plant growth and it is the main factor responsible for yield reductions in many crops. Water stress during drought limits the expansion of cells which results to restricted internode elongation and leaf expansion. It also causes losses in water content of plant tissues thus reducing cell rigidity. This inhibits enlargement and division of cells resulting to reduced plant growth and dry mass accumulation.[1]
The application of biostimulants such as amino acids was found to give positive effects on crops affected by environmental stresses such as drought. The importance of amino acids in plant development comes from their wide use in biosynthesis of different non-protein nitrogenous compounds such as vitamins, coenzymes, pigments, purine and pyrimidine bases.[2] Moreover, studies have shown that amino acids directly and indirectly affects the plant yield and development [3]
Root Development
The allocation of growth between the shoots and roots is a process that highly depends on environmental conditions. Nitrogen supply is a major determinant in this growth distribution process. A more general idea of nitrogen effects on plant biomass allocation is that at high rates of N supply, plants sense a decreased need for nitrogen uptake and results to decreased root growth and an increase need for carbon uptake and, hence, for shoot growth. Plants fed with high levels of nitrogen increases in shoot length but not the lateral length of its roots.
Amino acids serve as nitrogen sources for plants and has several advantages over inorganic sources of nitrogen with respect to the development of plant’s root system. Too much inorganic nitrogen absorbed by plants makes it vulnerable when subjected to water stress. High concentrations of nitrates (NO3-) result to inhibition of flow of auxins. Auxins are
plant hormones that have significant role in coordination of many growth and behavioral processes in the plant’s life cycle and are essential for plant body development including lateral root development [6] . Thus, high concentrations of chemical fertilizers result in increased above-soil growth but poor root development. This problem is magnified during drought when the undeveloped root system cannot hold enough water to sustain plant growth.
To overcome environmental stresses, plants need to modify root structure to enable them to forage heterogeneously distributed nutrients in the soil. Foraging response normally involves increased proliferation of lateral roots. Amino acids, specifically L-glutamate has been shown to induce foraging mechanism. This is characterized by slowing of primary root growth and increased root branching which increases the precision of root placement within the soil. [6]
Furthermore, there is strong evidence that both mycorrhizal and non-mycorrhizal plants in a variety of ecosystems directly absorb amino acids from the soil and through foliar feeding. Plants that have access to organic N directly would no longer have to rely on microbial mineralization to produce N from inorganic sources-which is generally considered to be bottleneck in the N cycle in soils. [6]
Osmotic Regulation During Drought
Osmotic pressure plays a fundamental role in water stress responses and growth in plants. Cell growth due to expansion of cell is regulated by turgor pressure, which is the force against the plant’s cell wall. This is maintained by osmotic regulation through osmotically active substances. If the soil supplies moisture as fast as the air removes it, then the osmotic pressure must be low. As the air removes more and more water and the water content of the plant tissue is
drawn upon in order to supply the demand, then, so long as the osmotically active substances remain constant, the osmotic pressure rises proportionately.
Free amino acids are osmotically active substances that contribute in osmotic pressure adjustments during drought. Amino acids keep osmotic potential of cells negative, thus keeping the cell wall rigid and keep cells from shrinking due to dehydration. [7] Exogenous amino acids modulate membrane permeability and ion uptake which is how amino acids mitigate drought or even salt stresses. [8]
The effects of drought (water deficient stress) can be greatly reduced when applied with Amino Acid through foliar feeding. A study in corn revealed up to 30% more yield (in terms of mass per 1000 grains) when sprayed with amino acid under water deficient conditions. The study revealed that spraying of amino acids before water deficient stress is up to 20% more effective than spraying amino acid after water deficient stress. [9] Another study on wheat revealed that amino acid reduced damage due to stress by 70% when applied at a concentration of 1 mL per Liter. [10]
Water stress interferes with photosynthesis, hormone production, respiration, plant mineral nutrition through roots. It also disturbs transportation of nutritional elements and assimilates from one part of the plant to another. Amino acids can be used as an effective supplementation to manage the negative effect on crop development caused by poor water availability.
Actual Field Experience
During the latter part of 2014, the country experienced dry spells which affected the crops. The announcement of the El Niño phenomenon by the PAG-ASA has greatly influenced the decision of some corn farmers not to plant during the current season. But some farmers, especially those with no other sources of income, have to gamble and plant despite the warning. For this reason, the agricultural industry specifically the seed companies was beset by numerous problems
which include quality complaints since hybrid corn varieties are tested based on its tolerance on drought. However, there were farmers who emerged successful.
One of the success stories on field is that of Mr. Alfredo Yao of Wao Lanao del Sur. According to him, at 2 to 3 leaf stage of his corn plant he used Amino Plus Foliar Fertilizer. Much to his dismay, days after spraying there was no rain for more or less two weeks. Most of the corn plants adjacent to his area showed symptoms of heat stress. However, much to his delight, his corn plants exhibited a better tolerance. He also observed that when it finally rained, his plants grew faster compared to that of his neighbor even though they are using the same seed variety and that the neighboring farm was using larger amounts of inorganic fertilizer. Upon harvest, his neighbor complained of poor tip filling while he produced healthy cobs. His average yield is 6 tons per hectare with only 4.9 sacks of inorganic fertilizer and 2 Litres of Amino Plus
Foliar Fertilizer per hectare. His neighbor barely produced 4 tons per hectare despite using 12 sacks of inorganic fertilizer per hectare.
Another successful user of Amino PlusFoliar Fertilizer is Mr. Sofronio Tamayao of Solana Cagayan (Region 2), Luzon. He used Amino Plus at 26 days leaf stage in addition to inorganic fertilizers. Thinking that his inputs may be wasted because of the insufficient rain, he did not apply another spray round of Amino Plus. However, Mr. Tamayao observed that compared to his neighbors, his corn plant showed less stress symptoms after almost a month of no rain. Moreover, he was able to harvest 12.3 tons from his 1.2 hectare corn higher than his usual 8-10 tons in the previous croppings of the same area.
Ian Bael of Wao Farms Enterprises had wondered why Mr.Julius Laurilla of Wao, Lanao del Sur made several repurchase of the product. Upon interview, Mr. Laurilla confessed that he observed that despite the insufficient rain his corn plants showed lesser signs of stress. Thus, he decided to use Amino Plus Foliar Fertilizer in his whole corn area and hoped that when the rains would come, his corn field would yield a better harvest.
Mr. Sabas Rusora , a vegetable farmer from Lantapan also noticed that his tomato seedlings grew faster after applying Amino Plus Foliar Fertilizer, and he was able to plant at nine days after sowing which normally took 14 to 15 days. He based his decision and confidence to plant early at 9 days on the height and vigor of seedlings. After transplanting he noticed that the plants grew fast even though the rain was scarce during that period. The experience made him a loyal user of Amino Plus Foliar Fertilizer.
These are the only few success stories of Amino Plus Foliar Fertilizer users whose crops became more resistant against stress caused by drought. As long as moisture in the soil has not completely exhausted, Amino Plus can help support plant development by improving soil structure and osmotic regulation of plant cells. From various testimonies of Amino Plus users, it is clear that the product has successfully fulfilled its role of increasing resistance of crops even during drought season.
References:
[1] Delfine, S., Tognettir, R., Loreto, F., Alvino, A., 2002. Physiological And Growth Responses To Water Stress In Field Grown Bell Pepper (Capsicum Annuum, L.). J. Hort. Sci. Biotechnol. 77 (6), 697–704.
[2] Salwa A.R. Hammad & Osama A.M. Ali B (2014) Physiological And Biochemical Studies On Drought Tolerance Of Wheat Plants By Application Of Amino Acids And Yeast Extract, Annals Of Agricultural Sciences, 59 (1) Pp 133-145
[3] Mohamed, A.M., 2006. Effect Of Some Bio-Chemical Fertilization Regimes On Yield Of Maize. M.Sc. Thesis, Fac. Of Agric., Zagazig Univ., Egypt, Pp. 70-177.
[4] Raab T.L. Et Al (1996) Non-Mycorrhizal Uptake Of Amino Acids By Roots Of The Alpine Sedge Kobresia Myosuroides: Implications For The Alpine Nitrogen Cycle, Oecoloigia Vol. 108, Pp 488-494
[5] Stribley Dr Read Dj (1980) The Biology Of Mycorrhizal Infection And The Capacity To Utilize Simple And Complex Organic Nitrogen Sources. New Phytol 86:365-37
[6] Pia Walch-Liu, Et Al (2006) Nitrogen Regulation Of Root Branching, Annals Of Botany
[7] D.R Cyr (1990) Accumulation Of Free Amino Acids In The Shoots And Roots Of Three Northern Conifers During Drought., Tree Physiology 6, Pp 293-303, Department Of Biology, University Of Waterloo, Canada
[8] V.K Rai (2002) Role Of Amino Acids In Plant Responses To Stresses. Biologia Plantarum Vol. 4 Pp 481-487
[9] P. Kasraie Et Al (2012)The Effects Of Time Spraying Amino Acid On Water Deficit Stress On Yield, Yield Component And Some Physiological Characteristics Of Grain Corn, Scholars Research Library
[10] Azimi M.S. et al (2013)Evaluation of Amino Acid and Salicylic Acid application on yield and growth of wheat under water deficit, International Journal of Agriculture and Crop Sciences, Vol. 8 pp 816-819
This appeared in Agriculture Monthly’s January 2016 issue.
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