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The interaction of arbuscular mycorrhizal fungi (Glomus etunicatum, Glomus intraradices, and Glomus versiforme) with a wilt-causing soil-borne pathogen, Verticillium dahliae, was studied in cotton. It was found that establishment by arbuscular mycorrhizal fungi reduced disease index. In diseased cotton plants colonised by G. etunicatum, the disease index was less than other diseased mycorrhizal and non-mycorrhizal ones. In diseased cotton plants, chlorophyll content was lower than others. Three Glomus species significantly increased content of sugar and protein in shoot and root. Pathogen-infected plants had higher proline concentration in shoot and root than healthy plants. On the other hand, the increased content of proline as stress sensor showed that Verticillium accelerates senescence and reduces yield. These results suggest that the beneficial effects of mycorrhiza can alleviate the pathogenesis effects of V. dahliae partly, and also there is a competitive interaction between the pathogenic and symb...

The interaction effects of kinetin and flooding on growth indexes, chlorophyll content, and the activity of 5-aminolevulinic acid dehydratase (ALA-D; EC 4.2.1.24) in seedlings of corn (Zea mays L. cv. 704) were investigated. Samples were taken 48, 96, 144, and 192 h after the start of treatment. Growth criteria (root length, shoot height, and dry weight) were inhibited more in flooded plants than in control plants. The pattern of growth changes was similar to chlorophyll a and b, as well as ALA-D activity. The exogenous application of kinetin (100 ppm) nullified the resulting decrease in growth and chlorophyll, but only partially reduced the suppression in ALA-D activity. These results indicate that recovery of flood-induced injury and restoration of normal conditions was maintained either partially or completely by the application of kinetin. This recovery might have been the result of the action of several hormones, which can trigger internal cellular metabolism and induce changes in the ratios of growth regulators.

The objective of this study was to evaluate the effects on the structure and ultrastructure of pepper plants (Capsicum longum A.DC.) exposed to UV radiation under greenhouse conditions. The plants were grown in a growth chamber under uniform environmental conditions and after 35 days were exposed to UV-A and UV-C radiation for 15 and 8 days, respectively. Changes in root growth were not significant, but shoot growth decreased in UV-R-exposed plants and decreased significantly in UV-C-exposed plants. Leaf area also decreased in UV-R-exposed plants and decreased significantly in UV-C-exposed plants. Root thickness was not affected by UV treatment, but stem and leaf thickness significantly increased in response to UV-A and UV-C treatment. Stomata increased in number and size in UV-R-exposed plants. At the ultrastructural level, chloroplast thylakoids were dilated and starch reduction was observed. UV treatment resulted in the formation of crystals in the peroxisomes of mesophyll cells. The formation of these crystals was due to an increase in catalase activity, which is an antioxidant enzyme. The study shows that pepper plants were sensitive to UV and the findings provide insight into the physiological changes during UV exposure, and indicate this plant was more sensitive to UV-C radiation than to UV-A radiation.

Copper is an essential micronutrient for plant growth. It is an important component of proteins. In the present research the effect of copper toxicity on chlorophyll, sugar, protein content and antioxidant enzymes activity in both mycorrhizal and non-mycorrhizal tomato plants were studied. The experiment was performed by using two treatments (mycorrhizal and non-mycorrhizal) and five concentrations of CuSo4 solution added to Hogland nutrient solution . Copper toxicity caused reduction in growth in all treatment (non-AM). It may be due to accumulation of Cu in leaves. Total sugar content in both shoot and roots, the total chlorophyll content in leaves, Protein content in shoots and roots, antioxidant enzyme activity and root colonization were determined.

The objective of this investigation was to study the effects of three Glomus species: G. etunicatum, G. intraradices and G. versi- forme on the development of verticillium wilt in cotton plants. Results indicated that the influence of arbuscular mycorrhizal fungi as a biocontrol agents were different among three Glomus species. In diseased cotton plants colonized by G. etunicatum, the disease index was lower than others and also, higher colonization percentage was relevant to these plants. On the other hand, the establishment of mycorrhizal symbiosis and development of structure of AMF were reduced when both symbiotic and pathogenic fungi infected the same root. In addition, the symptoms of veticillium wilt were diminished too. These results revealed that the beneficial effects of mycorrhiza could alleviate the pathogenic effects of V. dahliae and also a competitive interaction existed between these pathogenic and symbiont fungi.

SummaryAn adequate supply of oxygen, to maintain aerobic metabolism, is essential during the storage of apples. One of the recommended conditions for storing Cox’s Orange Pippin apples is in 1.8 to 2.5% oxygen; sometimes this is attained by admitting nitrogen to the store. Inaccurate estimation of the oxygen content of the store can result in the fruit being deprived of oxygen and in the accumulation of alcohol in the tissues. If aerobic conditions are re-established, the alcohol content of the fruit decreases, but if the concentration is of the order of 200 mg alcohol/100 g fruit the apples become senescent before they lose the alcoholic flavour.It has been suggested elsewhere that a preliminary anaerobic phase, lasting for a week at 3.5 °C, leads to improved turn-out of apples from C.A. storage. For the English cultivars tested this has not proved to be the case. Accidental or deliberate anaerobiosis is detrimental in other respects, apart from the accumulation of alcohol; losses from rotting are increa...