The effects of the ethylene precursor ACC and two inhibitors, AgNO3 and AVG, on root formation were tested in in vitro shoots of passion fruit (Passiflora Midis f.flavicalpa Deg.). The organogenic response was assessed on the basis of percentage of shoot-forming. roots, root number and length. The time course of eth...ylene production was also monitored. ACC inhibited root formation by delaying root emergence and increasine, callus formation at the basis of the shoots. In addition, ACC caused a marked increase in ethylene production, coupled to leaf chlorosis and senescence with lower rooting frequencies, number and length of roots. IAA supplementation increased ethylene production. Both ethylene inhibitors, AgNO3 and AVG, at appropriate concentrations reduced callus formation at the basis of shoots. AVG increased the number of roots per shoot, but drastically reduced length of differentiated roots. Regarding to leaf pigments, ACC promoted a marked reduction on carotenoids and total chlorophyll, whereas AVG and AgNO3 delayed explant senescence and pigments degradation, not differing from IAA supplemented and non-supplemented control treatments. The results confirm previous reports on the beneficial effects of ethylene inhibitors on in vitro rooting and suggest its reliability to be used as an alternative approach to evaluate sensitivity of Passiflora species to ethylene.
A detailed examination of the production of ethylene and other ripening parameters during storage period has been undertaken in transgenic apple fruits, where the ethylene biosynthesis was inhibited by antisense ACS (l-aminocyclopropane-l-carboxylate synthase) gene. Data indicate down regulation of ethylene production, softening and spoilage in... some transgenic lines. In some cases ethylene production was inhibited for over 90 percent, considerable reduction of softening and spoilage was observed probably due to the reduced activity of cell wall degradable enzymes. ACS activity was also monitored during ripening. The fruits of the best transgenic lines could be stored for minimum 4-5 months longer under 5 °C cold room storage conditions and one month longer at normal room temperature. This molecular approach can provide an alternative way to replace the commonly used and costly atmospheric storage of fruits.
Dianthus chinensis and Dianthus caryophyllus varieties were tested for shoot regeneration from leaf and petal explants and transformed with Agrobacterium tuniefaciens strains (EHA 105 and LBA 4404) harbouring an apple derived ACS cDNA in antisense orientation in order to reduce ethylene production and influence the et...hylene dependant traits in carnation. After transformation regenerating shoots were selected on MS medium containing 50-75-100-125-150 mg/1 kanamycin and supplemented with 1 mg/1 BA, 0.2 mg/1 NAA. Transgene integration was proved by PCR analysis with npt II spcific primers followed by Southern hybridisation of DNA isolated from green shoots on medium containing 150 mg/1 kanamycin. Several putative transformants were subjected to RT-PCR in order to examine the npt 11 expression at mRNA level. Both the transformant and the non-transformant plants were potted into glasshouse to observe the effect of changed ethylene production on flowering time, petal senescence and vase life.
Transgenic carnations were produced with an apple derived antisense ACC-synthase cDNA. Transgenic carnation regenerants were potted in glasshouse. All transformed plants showed normal growth and were true-to-type. Ethylene production — measured at full opening stage — lowered by 30-60 %, no plant with 100 % decrease was identified. The vase...-life has been observed for 5 years. 38 % of the transformant carnations showed a higher a relative value in days by more than 2 days to 6 days. Twenty six plants were found exhibiting the most marked alterations in the tested trait. In these plants ethylene production decreased by 37-67 %, they have longer vase-life (by 4 days or more). Since the fragrance variety 'Bíbor' was the plant material for genetic modification of vase-life, this trait has been conserved after transformation in spite of the fact that the position of transgene integration cannot be directed.
The effect of STS and 1-MCP on the postharvest quality of carnation and rose cut flowers was studied. Cut flowers of Dianthus c..aryophyllus L. cv. Asso and Rosa hybritia cv. Baroness were treated with silver thiosulfate (STS) at 0.4 mM with sucrose at 50 g 1-t and 1-methylcyclopropene ( I -MCP) at 0.5 g m<...sup>-3 for 611.
Pretreatment with STS and 1-MCP significantly extended the vase life and minimized the % loss of initial weight of carnation and rose cut flowers comparing to the untreated control. The two chemicals applied inhibited the chlorophyll degradation and carbohydrate loss and hence, significantly improved the postharvest quality of carnation and rose cut flowers comparing to the control. Ethylene production by cut flowers was inhibited as a result of using these chemicals. In general, there were no differences between STS and (-MCP but the later does not have the heavy metal implications of STS treatment, and hence, using 1-MCP pretreatment for extending the vase life of carnation and rose cut flowers was recommended.
Fruits are essential part of the human diet: they provide vitamins, minerals, antioxidants to the mankind. Physiologically they can be divided into two groups-climacteric and nonclimacteric - depending if they display any respiratory peak and dramatic increase in ethylene biosynthesis or do not. Ethylene is a gaseous hormone playing a very impo...rtant role in several physiological processes in plants. While climacteric fruits, like apples, bananas, tomatoes, peaches, apricots show increased ethylene biosynthesis and dramatic respiratory peak during their ripening, nonclimacteric fruits, like strawberries, grapes, citrus do not.
The most widely used fruits for studying nonclimacteric ripening are strawberries: several papers are focusing on the identification and characterization of ripening related genes from this plant. Therefore here we attempt to summarize the most important advances in strawberry fruit development, and ripening.
The most important components of fruit drop are: the rootstock, the combination of polliniser varieties, the conditions depending of nutrition, the extent and timing of the administration of fertilisers, the moments of water stress and the timing of agrotechnical interventions. Further adversities may appear as flushes of heat and drought, the...rainy spring weather during the blooming period as well as the excessive hot, cool or windy weather impairing pollination, moreover, the appearance of diseases and pests all influence the fate of flowers of growing and become ripe fruits. As generally maintained, dry springs are causing severe fruit drop.
In analysing the endogenous and environmental causes of drop of the generative organs (flowers and fruits), the model of leaf abscission has been used, as a study of the excised, well defined abscission zone (AZ) seemed to be an adequate approach to the question. Comparing the effects active in the abscission of fruit with those of the excised leaf stem differences are observed as well as analogies between the anatomy and the accumulation of ethylene in the respective abscission tissues.
The vase life of cut flowers and effects of various chemicals was examined with the help of a pulse treatment. According to the results using of chemicals (preservatives, disinfectants as well as blocking of synthesis of ethylene) is ineffective if it is used after seeding This shows the great importance of harvesting time.
Using 8-HQS...or l-MCP + 8-HQS proved to be the best for vase life in most of the samples. Using these materials did not prevent the appearance of air bubbles in the stems and absorption could be observed continuously.
To examine the tissue structure reaction of chemicals stems were stained with toluidin-blue, and high of absorption was measured. It was found that in cases, when absorption was bad, small air bubbles blocked the xylem vessels.
All the species examined (Aster linosyris, Achillea collina, Aster novi-belgii, Inula britannica, Solidago canadensis, Inula ensifolia, Senecio jacobea) show similar reactions to chemicals because they are the members of the same family.