effect of dust on chlorophyll fluorescence parameters and photosynthetic characters of sugarcane(Saccharum officinarum L.) in ahvaz

Extended Abstract
Background and Objectives
Sugarcane (Saccharum officinarum L.) is from poaceae trible and perennial native plant of asia continent warm areas. Ratio Fv/Fm estimates the maximum quantum yield of photosystem II. Under conditions of stress Fv/Fm decreased, this decreasing is due to low activity of reaction of photosynthesis centers and reducing of proteins that are responsible for water electron transport to chlorophyll a. Dust closed the pore openings and increased leaf temperature, lack of heat exchange, lack of transpiraition and loss of the entry of CO2 to leaves, on other hand dust accumulation on plant also creates a shadow on plant and decreases leaf photosynthesis. Since the maximum area under cultivation of sugarcane in the region, so studying the effects of dust on this growing phenomenon in the region seems to be necessary.
Materials and methods
This study aimed to examine the effects of dust, in a controlled environment greenhouse Development Research Institute of Sugarcane in the 2013-2014. In this experiment, dust courses and various concentrations of artificially applied. The experimental design was a randomized complete block design with 4 replications and 4 treatments. Treatments were: control (without dust), once a month, twice week, weekly dust apply. To isolate and correct actions dust on each treatment, the stool is made of metal with a half-inch galvanized pipe to a height of 2 meters, 3 meters in length and a width of one meter, was used. The stool was covered by a thin translucent plastic all interior and on both sides of it. The planting of cuttings CP69-1062 was used. Values of Fv/Fm (maximum quantum yield), NPQ (non photochemical quenching), qP (photochemical quenching), ΦPSII (efficiency of Photosystem two), SPAD number, photosynthesis rate, transpiration, leaf temperature, under stomatal CO2 concentration, electrolyte leakage, ascorbate levels, PAR and sugar content were measured.
Results:
The results showed that the dust, decreases the values of Fv/Fm, qP, ΦPSII, photosynthesis rate, transpiration flux, under stomatal CO2 concentration, PAR and sugar content but increases the amount of NPQ, SPAD number and leaf temperature. A significant positive correlation between stomatal conductivity with photosynthesis, transpiration and CO2 under stomata were observed that showed restrictions on the entry of gases into the cell. sugar production showed a significant decline. qP had highly correlated with Fv/Fm, and qP reducing, cause to reduce of Fv/Fm.
Discussion:
The result of dust stress and reducing of QA capacity, electron transfer into photosystem one reduced and causes a loss of light energy absorbed in the form of chlorophyll fluorescence excitation. In fact, during the excitation of chlorophyll, NPQ prevailed qP , and therefore, the quantum yield of photosynthesis reduced and the temperature of leaf increased because of stomatal closure and reduction stomatal conductivity and losses of energy in the form of light and heat grew. Sugar decreases because many enzymes involved in the sugars revival of the Calvin cycle are activated only with appropriate light intensity. Since the Fv/Fm component showed the highest correlation with most of the measured characters, so it can be use as a criteria along to the qP and NPQ for sugarcane studies under dust stress.