Diagnosis of the functional state of the photosynthetic apparatus Taraxacum officinale (L.) Weber ex F. H. Wigg. by the method of chlorophyll fluorescence induction

The informativeness is established of the method of induction of chlorophyll fluorescence for bioindication in the conditions of anthropogenic influence on the example of T. officinale plants, by the parameters: F0, Fm, Fst, Fv, Fv/Fm та k1, k2. The main parameters of the induction curve can be used as test indicators to determine the resistance of plants to adverse factors. Changes in these indicators characterize the processes associated with the influence of the environment on the course of both light and dark phases of photosynthetic processes in chloroplasts. The photosensitivity of T. offic- inale leaves, which indicates the physiological state of plants, decreases with increasing adverse external influences. It is established that the plants of T. officinale have the maximum intensity of photosynthesis, which grow in more favorable ecological conditions control. Therefore, the use of the device «Floratest» to determine the condition of plants at different levels of anthropogenic load is promising and requires further research.

Characteristics of the photosynthetic apparatus of Pinus sylvestris L. and Larix sibirica Ledeb. from different locations of the Irkutsk region (Eastern Siberia)

The characteristics of the photosynthetic apparatus of coniferous growing in various forest types and climatic conditions of the Irkutsk region (Taishet, Bratsk, Shelekhov, Irkutsk districts) have been explored. The content of photosynthetic pigments, total, free, and bound water in the needles of P. sylvestris and L. sibirica were studied. Using a pulse fluorimeter PAM 2500 (Waltz, Germany), the chlorophyll fluorescence in needles was measured based on such induction curve indices as Fv/Fm, Y(II), NPQ, and ETR. According to the chlorophyll fluorescence induction curve parameters of Scots pine and Siberian larch needles growing in different forest growth conditions, the most effective potential of primary photochemical processes in PSII was observed in Scots pine. While studying the pigment fund of Scots pine and Siberian larch needles, it was found that the highest values of the content of chlorophyll (Chl) a, b, and carotenoids were observed in P. sylvestris and L. sibirica growing in the climatic and forest growth conditions of the Shelekhov district. It is assumed that the revealed characteristics of the parameters reflect the processes of adaptation of the photosynthetic apparatus to various environmental conditions during vegetation development, as well as its high plasticity in different climatic growth conditions.

Chlorophyll Fluorescence - a Tool for Quick Identification of Accase and ALS Inhibitor Herbicides Performance

ABSTRACT: Chlorophyll fluorescence measurement is a precise research technique that can be used for studying the effect of herbicides with different modes of action on photosynthetic apparatus. The aim of the present project was to study the variation of the fluorescence induction curve (Kautsky curve) and its variables affected by pinoxaden (ACCase inhibitor) and mesosulfuron-methyl + iodosulfuron herbicide (ALS inhibitor) in littleseed canarygrass (Phalaris minor Retz.) and wild oat (Avena ludoviciana Durieu). This study was carried out at the Greenhouse of Collage of Agriculture at Ferdowsi University of Mashhad, during 2013. Experiments were performed based on a completely randomized design in form of a dose-response test with six doses of each herbicide plus an untreated control. The maximum quantum efficiency of photosystem II (PSII) was measured 1, 2, 3, 5 and 7 days after spraying (DAS). The results obtained in the study indicated that the estimated EDs parameters differed based on herbicide types or weed species. For example, ED90 varied from 11.67 to 28.61 g active ingredient (a.i.) ha-1. Moreover, the results showed that application of mesosulfuron-methyl + iodosulfuron at doses higher than 9 g a.i. ha-1 changed the shape of the chlorophyll fluorescence induction curve (Kautsky curve) in littleseed canarygrass at 7 DAS while herbicide doses of mesosulfuron-methyl + iodosulfuron did not change the shape of the Kautsky curve in wild oat. In addition, the Kautsky curve was observed to have an approximate permanent drop for littleseed canarygrass species at 2 DAS by pinoxaden. Comparing the fluorescence parameters in wild oat and littleseed canarygrass treated with two herbicides showed that Fv/Fm, the maximum quantum efficiency of PSII and Fvj, variable fluorescence at the J step of littleseed canarygrass decreased more than the mentioned parameters in wild oat. Furthermore, there was a strong relationship ranging from 0.53 to 0.79 between dry weights after 4 weeks and fluorescence parameters at 7 DAS depending on the herbicide type and weed species. Applying fluorescence parameters a few days after treatment to predict biomass production can be a defining criterion in research and development stages of herbicides to eliminate the need for whole plant bioassay. This method can also be applied to shorten the bioassay screening period and function as a suitable and cost effective indicator for monitoring of ACCase and ALS inhibitors. This approach also demonstrates serious damages to plant photosynthesis apparatus on crop during herbicide misapplication.