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Effects of Abscisic Acid

Plant hormones, also called phytohormones or photochromes, are organic compounds which regulate cell cycle processes. Produced in one part of the plant and transiting to another, phytohormones signal and either stimulate or inhibit chemical and structural changes within the plant. These changes include all manner of plant growth and development: cell division and differentiation and growth, seed germination, metabolism, fruit ripening, root formation and abscision. The most common phytohormones are auxins, gibberellins, cytokinins, ethylene and abscisic acid.

  1. Abscision

    • Abscisic acid also known as ABA, facilitates the sloughing off of fruits, flowers, leaves and sometimes small buds and branches. This shedding process is vital to homeostasis in the plant's relationship to the environment and within the plant itself. The shedding action permits dispersal of seeds and other reproductive structures and it returns plant-based nutrients to the soil. Within the plant, aging, injured, diseased parts are removed and the various parts of the plant organism are kept in balance.

    Plant Stress Hormone

    • In addition, abscisic acid signals seed germination, root growth, fruit ripening and bud dormancy. Further, abscisic acid controls the size of stomatal pores. These pores are intercellular space, minute openings, in leaves that allow for the exchange of oxygen and carbon dioxide and water vapor. At times, because of this capacity, abscisic acid functions as a stress hormone. For instance, in response to an environmental trigger such as drought, the abscisic acid level in a plant may increase, closing the stomatal pores and thus enabling increased water retention.

    The Role of ABA in Stress Tolerance

    • First isolated from cotton bolls in 1960, it has been known for decades that increased levels of ABA are triggered, in fact, by a variety of environmental stressors such as drought, water stress, cold stress, salt stress, desiccation stress, heat stress and wounding. The increased levels of abscisic acid enabled plant survival. Deciphering the code, discerning the mechanism underlying ABA synthesis and stress tolerance, then, has not solely been an academic concern. It bears directly on crop productivity, on the achievement of sustainable agriculture.

    Gene Discovery

    • Recently, per CBC News, Apr. 30, 2009, inroads to deciphering the code, to identifying "the gene that perceives ABA and turns that into a protective response have been made". Using a technique called chemical genomics, a group of research scientists from Canada, United States and Spain have identified four genes for proteins called receptors that bind to ABA and trigger a stress tolerance response. A scientific coup, this may lead to the synthesis of an ABA-like compound to be sprayed on plants during drought.

    ARS Research

    • In laboratories world-wide, intensive research in genetic engineering continues. This same mission is considered vital by the USDA Agricultural Research Service (ARS). In a recent national program report they state, "The demands placed on the national system of renewable resource production by a rapidly changing world can only be met by technologies that optimally harness the inherent genetic potential of plant, microbial, and insect germplasm. Production systems that optimally preserve and harness that genetic potential will maximize profits, security of supply, price stability, market competitiveness, and avoid crop losses from genetic vulnerability." (

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