Study On Characterstics Of Stomata Of Some Cut Flowers And Their Postharvest Regulation

Stomata are the channels of water vapour exchange between the plant and atmosphere, thus contributing to transpiration and water relations of plants, including the postharvest cut-flowers, and regulating stomatal opening can reduce water loss, and then maintain freshness and quality of cut flowers. This thesis focused on the main characteristics of stomata of several mainstreaming cut flowers and the effects of postharvest regulation of stomata opening on their water metabolism and ornamental quality. The major research results and conclusions were high-lighted below:1. Four common methods for plant stomatal observation, including directly shredding, oxhide gelatin blotting, nail polish blotting, scanning electron microscopy, were used to observe the stomata in leaves of cut carnations(Dianthus caryophyllus’Master’), lilies (Lilium’Conca d’Or’), roses (Rosa hybrida ’Movie Star’) and gerberas (Gerbera jamesonii ’Crossfire’). The results showed that directly shredding and scanning electron microscope methods were more applicable to observe and study the stomatal characteristics of above-mentioned cut flowers.2. The characteristics of stomata in leaves of above cut flowers, and especially stomatal distribution in different parts of cut roses and gerberas were investigated by scanning electron microscopy, respectively. Several results were obtained:(1) The density and size of stomata in leaves of the4cut flowers were very different, and their shapes were also different, for instance, the shape of stomata in carnation leaves was sub-orbicular, that of lily leaves was long-elliptical, and that of rose and gerbera leaves was elliptical;(2) Stomata of cut roses mainly distributed in the lower epidermis of leaf, and small amount of stomata were also found in some non-leaf organs and tissues such as leafstalk, lower epidermis of sepal, and stem surface;(3) Stomata of cut gerberas widely distributed in their non-leaf organs and tissues except upper epidermis of trans floret, ray floret and sepal, and much high stomatal density was observed in the disc floret, lower epidermis of sepal and the neck of stem.3. Effects of light/dark cycle and different spectrum of light on stomatal opening and water loss of cut roses and gerberas were investigated. The results showed that:(1) The response speed to light of stomata in different non-leaf organs and tissues were different, with the respect of stomatal opening rate of different parts of cut gerberas (after7h illumination of white light), and sepal stomata responded fastest, followed by stem stomata, and then ray floret stomata, and disc floret stomata responded slowest;(2) Under the condition of12h dark and12h light cycle, water loss of cut roses and gerberas both exhibited a circadian rhythm changes, i.e. water loss increased in the light and decreased in the dark, and a similar circadian rhythm of stomatal aperture of cut gerberas were also observed;(3) Stomatal opening and water loss of the detached leaves of cut roses, were significantly increased by illumination treatment with100μmol m-2s-1of different spectrum of light including white light, red light, green light and blue light, and the promoting effect of blue light were more stronger than that of the others.4. To research the roles of aquaporin in stomatal opening of cut flowers, the effects of a series of aquaporin regulators, including3inhibitors,1accelerator and1recovery agent, on stomata opening and water loss of cut roses or their detached leaves were investigated. Several results were obtained:(1) Stomatal opening of the detached leaves of cut roses induced by light could be significantly inhibited by soaking treatment for20min with aquaporin inhibitors including50μmol/L HgCl2,40mg/L AgNO3and20mg/L nano-silver, with similar inhibitory effect on stomatal aperture, though inhibitory effect of HgCl2treatment on stomatal opening rate was lower than that of AgNO3and nano-silver treatment. In addition, the inhibition of HgCl2on stomatal opening could be almost completely relieved by restoration treatment with β-mercaptoethanol. Furthermore, it was found that water loss of the detached leaves of cut roses in the light could be significantly inhibited by soaking treatment for20min with20mg/L nano-silver;(2) Stomatal aperture and stomatal opening rates of the detached leaves of cut roses in the light could be significantly promoted by soaking treatment with aquaporin accelerator (50μmol/L Forskolin);(3) Stomatal aperture and stomatal opening rates of leaves on cut roses in the light could be effectively inhibited by leaf spraying treatment with5,20,40mg/L of nano-silver, and the water loss of cut roses was also significantly reduced. Additionally, the leaf spraying treatment with40mg/L nano-silver can obviously the improve water relations of cut roses, and significantly delay the decrease in their fresh weight, extend the vase life and maintain the ornamental quality.