Localized Effects of Mechanical Wounding and Exogenous Jasmonic Acid on the Induction of Secondary Laticifer Differentiation in Relation to the Distribution of Jasmonic Acid in Hevea brasiliensis

The relationship between the effect of exogenous jasmonic acid (JA) on the induction of secondary laticifer differentiation and the distribution of JA in the seedling of Hevea brasiliensis Mull. Arg. was investigated with the aid of experimental morphological and radioisotope technique. Most radioactivity of H-3-JA sustained in treated site within one hour while no radioactivity was detected in new shoot and the radioactivity in upper leaf was much less than that in the parts below the treated site, suggesting that JA was mainly transported downwards in the shoot of H brasiliensis. Mechanical wounding hindered the entrance of exogenous JA remarkably while held back the entered JA to the regions around wounded site. The effect of exogenous JA and mechanical wounding on the induction of the secondary laticifer differentiation was limited to treated site where high level of JA was expected. Mechanical wounding reduced the effect of exogenous JA on the differentiation of secondary laticifer, which could be ascribed to the hindrance of mechanical wounding to the entrance of exogenous JA. It was concluded from the combined data that a high accumulation of JA was required for inducing the secondary laticifer differentiation in H. brasiliensis.

Response of Endogenous Salicylic Acid and Jasmonates to Mechanical Wounding in Pea Leaves

The roles of on endogenous jasmonates （JAs） and salicylic acid （SA） in wounding response were investigated. Pea （Pisum sativum L.） seedlings were treated with three different methods including mechanical wounding, JAs application, and SA application. The contents of endogenous JAs and SA, as well as the activities of the related enzymes were detected by enzyme-linked immunosorbent assay （ELISA）, high performance liquid chromatography （HPLC）, and spectrophotometer, respectively. The results showed that endogenous JA rapidly accumulated within 30 min after wounding. The increase in the activities of both lipoxygenase （LOX） and allene oxide synthase （AOS） lagged behind JAs burst. A second slight increase in JAs level was observed at 24 h after wounding treatment, and at the same time point, higher activities of LOX and AOS were also detected. Endogenous free SA content decreased accompanied with JAs burst. Effects of exogenous JA application were similar to those of wounding treatment on endogenous SA level and phenylalanine ammonia lyase （PAL） activity, whereas exogenous SA application led to the significant inhibition of LOX and AOS activities and the decrease of endogenous JAs level at the early stage of treatment. It is thus suggested that JAs burst and SA decrease in early response to wounding may constitute an important mechanism by which plant starts the related defense reaction and adapts to wounding stress.

Salt＇s Effect on Anatomy and Deformity of Pistacia vera Nut

This study attempts to examine the effects of salinity on leaf, stem, and nut of Pistacia vera （Ohady and Kaleh Ghochi cultivars） in order to characterize their anatomical structures with electron and light microscopy. A comparative study of the anatomy indicates a difference between the density of simple and glandular trichomes in leaf surface, deposit of wax, the thickness of leaf, the length of epidermal cells, palisade parenchyma cells, crystals in mesophyll, and the manner of compatibility to salinity. The results obtained in this research demonstrate that compatibility of Ohady cultivar is higher than Kaleh Ghochi and the degree of mechanical wounding depends on their development stages. In addition to results of previous studies which considered crop load as the main cause of fruit deformity. The present study indicates that, in spite of some reduction in total production of a tree, salinity decreases fruit deformity and to a high extent prevents the production of deformed fruit. Indeed, a remarkable reduction in production of deformed fruit will be yielded by selecting pistachio varieties which are resistant to salinity. Moreover, salinity increases the resistance of nuts to mechanical wounding. The results of this study suggest that in EC = 7.6, 12.6 deformity of nut is not related to crop load.

Responses of phospholipase D and lipoxygenase to mechanical wounding in postharvest cucumber fruits

This study was to investigate the responses of phospholipase D（PLD） and lipoxygenase（LOX） to mechanical wounding in postharvest cucumber（Cucumis sativus L.cv.Biyu-2） fruits.Membrane-associated Ca2＋ content,activities and gene expression of PLD and LOX,and contents of phosphatidylcholine（PC）,phosphatidylinositol（PI）,and phosphatidic acid（PA） were determined in cucumber fruits following mechanical wounding.Results show that PLD and LOX activities increased with the PLD and LOX mRNAs which are upregulated upon wounding,while membrane-associated Ca^2＋ content decreased.Accompanying with the increase of PLD and LOX activities,accumulation of PA and losses of PC and PI were observed in all fruits,but there were differences of degrees between wounded and control fruits.Results suggest that PLD and LOX might be the main hydrolytic enzymes of phospholipids in postharvest cucumber fruits participating in the mechanical wounding injury.The activation of PLD and LOX might be the result of gene expression,which could be This study was to investigate the responses of phospholipase D（PLD） and lipoxygenase（LOX） to mechanical wounding in postharvest cucumber（Cucumis sativus L.cv.Biyu-2） fruits.Membrane-associated Ca^2＋ content,activities and gene expression of PLD and LOX,and contents of phosphatidylcholine（PC）,phosphatidylinositol（PI）,and phosphatidic acid（PA） were determined in cucumber fruits following mechanical wounding.Results show that PLD and LOX activities increased with the PLD and LOX mRNAs which are upregulated upon wounding,while membrane-associated Ca2＋ content decreased.Accompanying with the increase of PLD and LOX activities,accumulation of PA and losses of PC and PI were observed in all fruits,but there were differences of degrees between wounded and control fruits.Results suggest that PLD and LOX might be the main hydrolytic enzymes of phospholipids in postharvest cucumber fruits participating in the mechanical wounding injury.The activation of PLD and LOX might be the result of gene expression,which could be stimulated by the Ca^2＋ flowing from the membrane to the cytoplasm upon receiving the wounding signals.

Nicotine Concentration in Leaves of Flue-cured Tobacco Plants as Affected by Removal of the Shoot Apex and Lateral Buds

It is believed that the nicotine concentration in tobacco is closely correlated with the amount of nitrogen （N） supplied. On the other hand, N uptake mainly occurs at the early growth stage, whereas nicotine concentration increases at the late growth stage, especially after removing the shoot apex. To identify the causes of the increased nicotine concentration in tobacco plants, and to compare the effects of different ways of mechanical wounding on nicotine concentration, field experiments were carried out in Fuzhou, Fujian Province in 2003 and 2004. Excision of the shoot apex had almost no influence on N content in the plant; however, it caused dramatic increases in nicotine concentration in leaves, especially in the middle and upper leaves. An additional increase of the nicotine concentration was obtained by removal of axillary buds. The wounding caused by routine leaf harvests, however, did not change the leaf nicotine concentration, and neither did reducing leaf harvest times. The present results revealed no direct relationship between N supply and nicotine concentration in tobacco leaves, and indicate that not all kinds of mechanical wounding were capable of stimulating nicotine synthesis in tobacco plants. Since nicotine production is highly dependent on the removal of apical meristems and hence on the major sources of auxin in the plant, and application of 1-naphthylacetic acid onto the cut surface of the stem after removing the shoot apex markedly decreased the nicotine concentration in different leaves and the total nicotine content in the plant, the results suggest that decreased auxin supply caused by removal of the shoot apex as a kind of mechanical wounding might regulate nicotine synthesis in the roots of tobacco plants.