title: Low Night Temperature Affects the Phloem Ultrastructure of Lateral Branches and Raffinose Family Oligosaccharide (RFO) Accumulation in RFO-Transporting Plant Melon (Cucumismelo L.) during Fruit Expansion.
abstract: Due to the importance and complexity of photo assimilate transport in raffinose family oligosaccharide (RFO)-transporting plants such as melon, it is important to study the features of the transport structure (phloem) particularly of the lateral branches connecting the source leaves and the sink fruits, and its responses to environmental challenges. Currently, it is unclear to what extents the cold environmental temperature stress would alter the phloem ultrastructure and RFO accumulation in RFO-transporting plants. In this study, we firstly utilized electron microscopy to investigate the changes in the phloem ultrastructure of lateral branches and RFO accumulation in melons after being subjected to low night temperatures (12°C and 9°C). The results demonstrated that exposure to 9°C and 12°C altered the ultrastructure of the phloem, with the effect of 9°C being more obvious. The most obvious change was the appearance of plasma membrane invaginations in 99% companion cells and intermediary cells. In addition, phloem parenchyma cells contained chloroplasts with increased amounts of starch grains, sparse cytoplasm and reduced numbers of mitochondria. In the intermediary cells, the volume of cytoplasm was reduced by 50%, and the central vacuole was present. Moreover, the treatment at 9°C during the night led to RFO accumulation in the vascular bundles of the lateral branches and fruit carpopodiums. These ultrastructural changes of the transport structure (phloem) following the treatment at 9°C represented adaptive responses of melons to low temperature stresses. Future studies are required to examine whether these responses may affect phloem transport.
authors: Beijing Key Laboratory of New Technique in Agricultural Application, College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China.
authors: Jinghong
authors: J
authors: Hao
authors: Institute of Agro-products Processing Science and Technology, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors: Fengying
authors: F
authors: Gu
authors: Institute of Agro-products Processing Science and Technology, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors: Jie
authors: J
authors: Zhu
authors: Institute of Protected Horticulture, Chinese Academy of Agricultural Engineering, Beijing 100125, China.
authors: Shaowei
authors: S
authors: Lu
authors: Key Laboratory of Protected Horticulture of Education Ministry and Liaoning Province, College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China.
authors: Yifei
authors: Y
authors: Liu
authors: Beijing Agricultural Technology Extension Centre, Beijing 100029, China.
authors: Yunfei
authors: Y
authors: Li
authors: Key Laboratory of Protected Horticulture of Education Ministry and Liaoning Province, College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China.
authors: Weizhi
authors: W
authors: Chen
authors: Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide 5001, Australia.
authors: Liping
authors: L
authors: Wang
authors: Beijing Key Laboratory of New Technique in Agricultural Application, College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China.
authors: Shuangxi
authors: S
authors: Fan
authors: Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide 5001, Australia.
authors: Cory J
authors: CJ
authors: Xian
mesh_terms: D003080:Cold Temperature; D019662:Cucurbitaceae / Q000378:metabolism* / Q000648:ultrastructure; D005638:Fruit / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D009844:Oligosaccharides / Q000378:metabolism*; D052585:Phloem / Q000378:metabolism* / Q000648:ultrastructure; D011887:Raffinose / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: D009844:Oligosaccharides; D011887:Raffinose