Characterization Of Stomata In Cut Carnations And Their Responses To Light

Carnation?Dianthus caryophyllus L.?is one of the mainstream cut flowers all over the world and is very popular among consumers.However,the cut carnations are prone to wilting and stem bending,which directly disrupted its ornamental quality and commodity value.Similar to other cut flowers,the symptoms of post-harvest water deficit in cut carnations are mainly due to the water loss exceeding the amount of water uptake.Stomata are the main channels for plants to exchange water and gas with their environment,which can modulate transpirating water loss via their opening and closing.For the case of cut flowers,it is usually believed that their water loss is mainly invoved in stomatal transpiration.However,there were some reports showed that stomata were observed in the non-leaf organs of cut flowers,which may play an innegligible role in their postharvest water loss.Thus,this thesis,using the cut carnation flowers?Dianthus caryophyllus?Master??as the experimental materials,firstly observed the stomatal distribution in different organs and tissues of this cut flower and their morphological characteristics;And then investigated the effects of different light intensities and light qualities on stomatal opening of the various parts of cut carnations and their water loss;Finally based on the RNA-seq analisis,the potential molecular mechanism of blue light responses of leaves on cut carnations was studied and discussed.The major results were as follows:1.The distribution and morphological characteristics of stomata in different organs and tissues of cut carnation flowers were investigated by scanning electron microscopy,respectively.The results showed that:?1?The stomata of cut carnations were mainly distributed in the epidermis of leaves and the outer epidermis of stems.There were also a number of stomata found in the outer epidermis of receptacles and sepals.However,there were no stomata in the inner and outer epidermis of petals,the outer epidermis of receptacles and sepals;?2?The stomatal density and size of the varius parts of cut carnation flowers were significantly different,and stomatal shapes were also variant,namely,the shape of stomata in the upper epidermis of leaves and the outer epidermis of receptacles were nearly circular,those of the lower epidermis of leaves and the outer epidermis of sepals were long-elliptical,and those of the outer epidermis of stem were elliptical;?3?The stomata in the outer epidermis of stems were the largest,which were even bigger than those in the epidermis of leaves;?4?The relative stomata area of the upper epidermis of leaves was larger than that of the lower epidermis,however both were larger than those of the other parts.2.The changes in water loss rate for intact,leaves-removed,and stem-only cut carnations over a 72-h vase period under an alternating 12-h light/12-h dark cycle were investigated.The results showed that:?1?The water loss rate of the intact and the leaves-removed cut carnations both exhibited a typical circadian rhythm change,and the former was significantly stronger than the latter.Besides,the water loss rate of the stem-only cut carnations also showed a weak circadian rhythm change;?2?The daily cumulative water loss of the intact cut carnations was significantly higher than that of the leaves-removed ones,and the latter was distinctly higher than that of the stem-only cut carnations.3.The effects of different light intensities on the stomatal opening and water loss of cut carnations were investigated.The results showed that:?1?The responses of stomatal opening of the various organs and tissues of cut carnation flowers to white light intensity were different,namely,the stomatal response of the upper and lower epidermis of leaves was the fastest,then followed by that of the outer epidermis of the receptacles,and that of the stem epidermis was the slowest;?2?With the increase of light intensity,the water loss of cut carnation flowers gradually increased,but there was no significant difference betweeen 50 and 100?mol m^–2 s^–1 of white light.4.The effects of different light qualities of 100?mol m^–2 s^–1 on the stomatal opening and water loss of cut carnations were further investigated.The results showed that:?1?The response speed to blue,red,green and white light of the stomata varied in different organs and tissues of cut carnations.For all the tested light qualities,the stomatal response of the upper and lower epidermis of leaves was the fastest,then followed by that of the outer epidermis of the receptacles,and that of the stem epidermis was the slowest;?2?Stomatal opening and water loss of the cut carnations were significantly increased by illumination treatment with 100?mol m^–2 s^–1 of blue,red,green and white light,and the promoting effect of blue light were the strongest,which was much stronger than those of the other light qualities;?3?There was no significant difference in promoting effects on the stomatal opening and water loss between red and green light.5.The RNA-seq results showed that:?1?There were 55219 Unigenes in the results of RNA-seq of leaves of cut carnations illuminated by blue light.The N50 value was 2009,and the Q30 of each one sample was above 95%,which proved that the RNA-seq was precise and reliable;?2?Total of 28869 annotations in the results of RNA-seq were obtained through blasting to several protein databases,which was 55.28%of the all of Unigenes;?3?Differential gene analysis was performed,and 3978 differentially expressed genes in the blue light treatment were selected.The KEGG enrichment analysis revealed that those genes were mainly involved in metabolic pathways,biosynthesis of secondary metabolites,carbon metabolism,and starch and sucrose metabolism,etc.6.Several Unigenes were selected for q-PCR experiments.Although there were some differences between the results of q-PCR and RNA-seq in several time points,the overall expression trends were consistent,which certified the reliability of transcriptome sequencing.The expression analysis of the genes related to stomatal movement showed that most of them were induced by blue light,but their response patterns were different.Some of them were up-regulated at 1 h after blue light treatment,and the others were up-regulated at 3 h.