Interactive effect of water deficit and bacterial pathogen Brenneria quercinia pathogen on leaf and stomata morphology in offspring of healthy and declined trees of Quercus brantii Lindl

One of the defense response strategies of trees against drought and pathogens is phenotypic variations of leaf and stomata. Also a certain mother tree can partly control phenotype of its offspring, and consequently, affect their tolerance to environmental stress. Therefore, in this study the effects of water deficit and bacterial pathogen on leaf and stomatal traits of healthy and dried trees, causing dieback of brant's oak in Kohgilouye and Boyer-Ahmad province, has been investigated.
Seeds of 4 healthy and 4 infected trees were collected from Khaeiz conserved area and planted into 320 pots to assess the effect of mother tree. After growing of seedlings, bacteria of Brenneria quercinia was inoculated to half of seedlings originated from both healthy and infected mother trees. After 40 days, half of the inoculated and non-inoculated seedlings, treated under water deficit for three weeks and the rest of them received full irrigation. Then, leaves of seedlings were harvested in September and leaf and stomata traits were measured by Image j 1.43 software. After that, the experiment was performed in a completely random design analyzed and the treatments were laid out in 2*2*2 (2 levels bacteria, 2 levels irrigation, 2 levels mother trees or genotype) and also the mean comparisons tests were done.
Results showed that the effect of bacteria is not significant on any stomata traits, but stomata width and stomata pore width were smaller in seedlings of water deficit treatment than fully irrigate seedlings. Also seedlings of dried trees had smaller stomata width. Water deficit caused to significant decrease of stomata perimeter and leaf width of half-sibling healthy trees, but number of leaf teeth and vein of half-sibling dried trees were decreased under water deficit treatment that they were not significant for half-sibling healthy trees. The affect of bacteria was not similar on half-sibling of healthy and dried trees, so that perimeter, area and length of stomata and perimeter and base angle of leaf in non-inoculated seedlings of healthy trees were larger but after inoculation stomata area of half-sibling healthy trees were decrease and stomata length increased significantly. Inoculation of bacteria also leads to significant decrease of leaf area in half-sibling dried trees but it did not have any affect on half-sibling healthy trees. Triple interaction of irrigation, bacteria and mother trees was significant for stomata pore width, as so, seedlings of healthy trees showed smaller stomata pore width under water deficit treatment, but bacteria has not negative effect on it. For seedlings of dried mother trees, these differences were not significant at any treatments, but size of it was smaller than seedlings of healthy mother trees.
Results of this study showed that half-sibling healthy trees have larger leaf and stomata traits. It demonstrated that these seedlings have more ability to production and photosynthetic capacity. Also the water deficit had more negative effect than bacteria on decline of oak. Also half-sibling of healthy trees under water deficit condition could reduce evaporation with decreasing size of leaf and stomata traits. This decreasing size of stomata were observed under inoculation of bacteria, in contrary the offspring's of drought affected trees exhibited longer stomata than controls that made them more susceptible to water deficit stress and pathogen agent. Also it has been demonstrated that stomata and leaf characteristics can conducted to identification of drought and bacterial disease resistance genotypes.