title: Effects of low sink demand on leaf photosynthesis under potassium deficiency.
abstract: The interaction between low sink demand and potassium (K) deficiency in leaf photosynthesis was not intensively investigated, therefore this interaction was investigated in winter oilseed rape (Brassica napus L.). Plants subjected to sufficient (+K) or insufficient (-K) K supply treatments were maintained or removed their flowers and pods; these conditions were defined as high sink demand (HS) or low sink demand (LS), respectively. The low sink demand induced a lower photosynthetic rate (Pn), especially in the -K treatment during the first week. A negative relationship between Pnand carbohydrate concentration was observed in the -K treatment but not in the +K treatment, suggesting that the decrease in Pnin the -K treatment was the result of sink feedback regulation under low sink demand. Longer sink removal duration increased carbohydrate concentration, but the enhanced assimilate did not influence Pn. On the contrary, low sink demand resulted in a high K concentration, slower chloroplast degradation rate and better PSII activity, inducing a higher Pncompared with HS. Consequently, low sink demand decreased leaf photosynthesis over the short term due to sink feedback regulation, and potassium deficiency enhanced the photosynthetic decrease through carbohydrate accumulation and a lower carbohydrate concentration threshold for initiating photosynthesis depression. A longer duration of limited sink demand and sufficient potassium supply resulted in a higher photosynthesis rate because of delayed chloroplast degradation. This finding indicates that the nutritional status plays a role in leaf photosynthesis variations due to sink-source manipulation.
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Wuhan 430070, China; Microelement Research Center, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Yonghui
authors.initials: Y
authors.lastname: Pan
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Wuhan 430070, China; Microelement Research Center, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Lu
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Wuhan 430070, China; Microelement Research Center, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Jianwei
authors.initials: J
authors.lastname: Lu
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Wuhan 430070, China; Microelement Research Center, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Xiaokun
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Wuhan 430070, China; Microelement Research Center, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Rihuan
authors.initials: R
authors.lastname: Cong
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Wuhan 430070, China; Microelement Research Center, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: rentao@mail.hzau.edu.cn.
authors.forename: Tao
authors.initials: T
authors.lastname: Ren
mesh_terms: D029688:Brassica napus / Q000033:anatomy & histology / Q000166:cytology / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D025461:Feedback, Physiological; D035264:Flowers / Q000033:anatomy & histology / Q000166:cytology / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D010788:Photosynthesis / Q000502:physiology*; D018515:Plant Leaves / Q000033:anatomy & histology / Q000166:cytology / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D011191:Potassium Deficiency / Q000378:metabolism*
chemical_list: D002734:Chlorophyll; D002245:Carbon Dioxide; D011188:Potassium
keywords: Brassica napus L.; Carbohydrate accumulation; K supply; Low sink demand; Photosynthesis suppression