COMPARATIVE CHARACTERISTICS OF PHOTOSYNTHETIC ACTIVITY OF NECTARINE CULTIVARS AND FORMS WITH DIFFERENT COLORED LEAF PLATE

Genotypes of nectarine with red leaves were created in Nikita botanical gardens.They have commercially valuable properties and biological characteristics (resistanceto powdery mildew, large-fruited, the ability of transmitting the trait of redleaves with constant result to progeny seed, etc. ). The aim of our researches was tostudy the main indicators of photoactivity of leaf apparatus of nectarine with greenand anthocyanin leaves coloration. Investigations have been carried out in 2010-2015 on intact leaf plates for three cultivars and forms of nectarine with greenleaves – Rubinoviy-8 (control), Chemus, Krymtsuht 53-85 and 2 forms withanthocyanin coloration of leaf plate (NektadianaKrasnolistnaya 996-88, Krasnola495-86). Photosynthetic activity was characterized by chlorophyll fluorescenceparameters (Kautsky effect). The content of chlorophyll a and b were determinedby spectrophotometry. The cultivar Rubinoviy-8 and the form - Krasnola 495-86were selected according to intensity indicators of the primary reactions ofphotosynthesis. Anthocyanin forms concede cultivar Rubinoviy-8 in efficiency ofthe primary reactions of photosynthesis an average of 48-50%; but they exceednectarines Chemus and Krymtsuht 53-85 with green color of leaves of 23-25%.The efficiency of energy supply in the "dark" reactions of photosynthesis in allvarieties and forms of nectarine maintained within 41-46%. But the further abilityto utilize received energy is most efficiently implemented at the nectarine cultivarRubinoviy-8 and form Krasnola 495-86. The forms of red-leaved nectarine incomparison with traditional cultivars are distinguished by a great potential forretaining the stability and productivity of the functioning of the photosyntheticapparatus.

(454) Detecting Plant Stress by Chlorophyll Fluorescence

The stress level in a plant may be directly associated with the intensity of the Kautsky effect (the sudden increase in fluorescence emission by chlorophyll following a dark adaptation). The decrease in photosynthetic efficiency, linked with the rate of photochemistry of plants under stress, provides a definitive signature (graphical pattern) that can be quantified and monitored, even for plants that have no visible stress symptoms. Using a prototype GrowScanner®, signature differences in plants under nitrogen and water stress, as compared with plants not under stress, could be detected and measured. Returning stressed plants to a nonstressed condition returned the stress signatures to that of control plants not under stress. Development of the technology may provide a relatively quick, presymptomatic methodology for detecting plant stress without sacrificing plant tissue.

Distribution and Effects of Bentazon in Crop Plants and Weeds

The inhibition of photosynthetic CO2-assimilation and of the variable chlorophyll fluorescence as well as uptake and transport of 14C-labelled bentazon and the possibilities for a herbicideinduced shade-type modification of the photosynthetic apparatus were investigated in bentazonsensitive weeds (Galium, Sinapis, Raphanus) and in the tolerant crop plants wheat and maize.1. In weeds the depression of photosynthetic CO2-assimilation is irreversible, whereas tolerant plants recover due to the metabolization of the active herbicide.2. A lower rate of uptake and transport of bentazon associated with its fast metabolization is the reason for the tolerance of crop plants towards bentazon.3. The transport of [14C]bentazon proceeds in the tracheary elements of the xylem. Uptake and transport of bentazon in the weeds are light dependent.4. The loss of variable fluorescence (Kautsky effect) in the leaves after root application o f bentazon proceeds much faster at high-light than at low light conditions and confirms the light-dependency of the bentazon transport.5. In the sensitive dicot weeds bentazon not only inhibits photosynthetic electron flow and depresses CO2-fixation but also induces the formation of shade-type chloroplasts which are less efficient in photosynthetic quantum conversion. This bentazon-induced modification of the photosynthetic apparatus (e.g. changes in ultrastructure, pigment ratios, and levels of chloro-phyll-proteins) contributes to the effectiveness of bentazon as a herbicide.