Growth regulators influence on stability of shoots and ascorbic acid content at cadmium and nickel joint action

It is shown that for a maize the most effective protector of cadmium and nickel influence was zeastimulin, for a pea – agrostimulin.A protective function of emistim C for both cultures was insignificant. It is set that zeastimulin is influential in the increased metals absorption of a root system, however substantially (on 15% for a nickel and twice for a cadmium) reduces their translocation to above-ground part of plants. Previous treatment of pea seed by agristimulin also intensified the accumulation of nickel roots on 60% and did not influence on cadmium absorption and toxicants translocation to tissues of assimilatory organs. The protector role of growth regulators to cadmium and nickel joint influence shows up in the increase of ascorbic acid maintenance in the roots cells of both species to 34%, where as in leaves – at a maize resulted in the lowering of vitamin С amount (on 28%), but at a pea – increase on 20%

ASCORBIC ACID IN PLANTS: METABOLISM AND FUNCTIONS

Аскорбiнова кислота (вiтамiн С) є найбiльш поширенимантиоксидантом у рослинах. Охарактеризовано можливi шляхибiосинтезу вiтамiну С у рослин, зокрема через ГДФ-d-манозу та lгалактозу. Наведенi молекулярно-генетичнi докази, а також вiдмiнностiвiд бiосинтезу у тваринних органiзмiв. За винятком останнього етапу,який протiкає на внутрiшнiй мiтохондрiальнiй мембранi, бiосинтезаскорбату у рослин вiдбувається в цитозолi. Узагальнено лiтературнiданi щодо вмiсту аскорбiнової кислоти в тканинах i органах рiзнихсiльськогосподарських, культурних i дикорослих рослин та фактори, щона нього впливають. Проаналiзовано особливостi метаболiзму аскорбiновоїкислоти, спiввiдношення вiдновленої й окиснених ї ї форм за рiзнихфiзiологiчних станiв, а також шляхи деградацiї вiтамiну С у рослин.Розглянуто основнi функцiї аскорбiнової кислоти в рослинних органiзмах.Обговорена ї ї участь як кофактора в синтезi збагачених гiдроксипролiномглiкопротеїнiв клiтинної стiнки, роль у контролi клiтинного подiлу таросту розтягуванням, захистi вiд активних форм кисню й оксидативногостресу, фотоокислення та регенерацiї вторинних антиоксидантiв, такихяк α-токоферол, а також функцiонування як коферменту в рiзнихфiзiолого-бiохiмiчних процесах у рослин.Ascorbic acid (vitamin C) is the most common water-solubleantioxidant in plants. Several possible pathways of vitamin C biosynthesis inplants in contrast to the only pathway of biosynthesis in animals have beendescribed. With the exception of the last stage, which takes place on the innermitochondrial membrane, ascorbate biosynthesis in plants occurs in the cytosol.The literature data on the content of ascorbic acid in the tissues and organsof various agricultural, cultivated and wild plants and the factors influencingit are summarized. The peculiarities of ascorbic acid metabolism, the ratio ofascorbatereduced and oxidized forms at different physiological states and theways of vitamin C degradation in plants are analyzed.The main functions of ascorbic acid in plant organisms are considered.Including evidence of its participation as a cofactor in the synthesis ofhydroxyproline-richproteins of cell wall, its role in controlling cell division andgrowth by elongation, protection against reactive oxygen species and oxidativestress, photooxidation and regeneration of secondary antioxidants such asα-tocopherol as well as functioning as a coenzyme in various physiologicaland biochemical processes in plants.However, the functions of this vitaminand the pathways of its biosynthesisstill need to be clarified. The content of ascorbic acid in plants is determinedby many processes that occur simultaneously, and the regulation of itsaccumulation requires their coordinated work. This occurs not only duringthe normal functioning of plants, but also under stressful conditions, whichare usually accompanied by increased biosynthesis and the use of ascorbate.At the same time, for a comprehensive assessment of the role of ascorbicacid in plant metabolism, it is necessary to simultaneously study the entireascorbate system, including dehydroascorbic, 2,3-diketogulonic acid, which isformed during irreversible transformation due to rupture of the lactone ringthe above compounds. Such approaches to vitamin C research are promising.Knowledge of the regulatory mechanisms of metabolic processes in general, andin particular the regulation of biosynthesis of physiologically active compounds,such as ascorbic acid, is relevant for plant physiology in connection withthe prospect of biotechnological use of plant objects to obtain importantmetabolites