Circadian rhythm of root pressure in popular and its driving factors

doi:10.17521/cjpe.2016.0098

Abstract

Abstract:

Aims Our main purposes were to investigate root pressure and its circadian rhythm of excised roots in ‘84K’ popular (Populus alba × P. glandulosa) cultured in soil and solution, to explore the influencing factors and their relationships with root pressure systematically and to understand the generation and rhythm regulation of root pressure. Methods We investigated the root pressure of excised roots in ‘84K’ popular using the method of digital pressure transducer. The diurnal rhythm of excised roots was conducted through different experimental treatments including sampling in different time, defoliation and girdling, together with ambient condition like soil temperature, differential or consistant temperature during day and night. Then we discussed the effects of root respiration and hydraulic conductivity on root pressure by further using chemical inhibitor. Furthermore, diurnal variation of osmotic potential and ions content as well as soluble sugar content of exudation was determined in order to explore their relationships with root pressure rhythm. Important findings Root pressure of excised roots in popular had diurnal rhythm which was higher during daytime and lower overnight. It reached its peak value in the morning to noon and valley value at 20:00. Root pressure of excised roots sampled at different time and cultured in different medium had influence on the rhythm of root pressure to some degrees, but did not the general rhythm of high in daytime and low overnight. Defoliation, girdling and the inhibitors for root respiration or cytomembrane hydraulic conductivity could affect the maximum value of root pressure while have no significant influence on the daily rhythm. Defoliation, girdling and respiration inhibitor reduced the maximum value of root pressure, whereas the hydraulic conductivity inhibitor had little influence on root pressure. The maximum value of root pressure declined with the decrease in soil temperature which could change the rhythm of root pressure. The synchronous change in the maximum value of root pressure and root respiration rate with temperature indicated that root respiration contributed to the change of root pressure along with temperature. Osmotic potential of root exudation was higher during the daytime and lower at night. Diurnal variations of ions and soluble sugar content of exudation were consistant with that of osmotic potential. The peak of root pressure measured under the condition of differential temperature during day and night was significant higher than that measured under constant temperature. In conclusion, root pressure of the poplar ‘84K’ showed significant diurnal rhythm, i.e. higher during the daytime and lower at night. The maximum value of root pressure was mainly regulated by root respiration metabolism. The factors such as respiration inhibitor, respiration substrate and temperature influence the value of the maximum root pressure of poplar ‘84K’. Root hydraulic conductivity had no significant influence on root pressure.

Key words: root pressure, excised roots, diurnal rhythm, influencing factors

Jian-Rong GUO, Xian-Chong WAN. Circadian rhythm of root pressure in popular and its driving factors[J]. Chin J Plan Ecolo, 2017, 41(3): 369-377.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2016.0098

https://www.plant-ecology.com/EN/Y2017/V41/I3/369

Figures/Tables 10

Fig. 1 The circadian rhythm of root pressure measured at different time of a day.

Fig. 2 The root pressure measured under different soil temperatures.

Fig. 3 The maximum of root pressure and respiration rate measured under different soil temperatures (mean ± SD, n = 6).

Fig. 4 The root pressure under constant temperature during day and night (25 °C/25 °C) and different temperature during day and night (25 °C /19 °C).

Fig. 5 Effects of defoliation and girdling on root pressure.

Fig. 6 Effects of inhibitors on root pressure.

Fig. 7 Effects of inhibitors on the maximum of root pressure (mean ± SD, n = 3-6, α = 0.05. CK, Control; T1, treatment 1, 0.1 mmol·L-1 HgCl2; T2, treatment 2, 1.0 mmol·L-1 NaN3; T3, treatment 3, 1.0 mmol·L-1 NaN3 + 0.1 mmol·L-1 HgCl2).

Table 1 Effects of inhibitors on root respiration rate and hydraulic conductivity (mean ± SD)

处理剂 Dispose dose	根系呼吸速率抑制率 Inhibition percentage of root respiration (%)	根系导水率抑制率 Inhibition percentage of root hydraulic conductance (%)
1.0 mmol·L^-1 NaN₃	44.07 ± 15.35^a	41.66 ± 14.83^a
0.1 mmol·L^-1 HgCl₂	23.16 ± 0.01^b	50.94 ± 31.37^a
1.0 mmol·L^-1 NaN₃+0.1 mmol·L^-1 HgCl₂	50.00 ± 4.55^a	44.04 ± 21.49^a

Fig. 8 Diurnal variation of osmotic potential of root exudation (mean ± SD, n = 6).

Fig. 9 Diurnal variation of ions and sugar in the exudation (mean ± SD, n = 6).

References 27

[1]	Cao KF, Yang SJ, Zhang YJ, Brodribb TJ (2012). The maximum height of grasses is determined by roots. Ecology Letters, 15, 666-672.
[2]	Clarkson DT, Carvajal M, Henzler T, Waterhouse RN, Smyth AJ, Cooke DT, Steudle E (2000). Root hydraulic condu¬ctance: Diurnal aquaporin expression and the effects of nutrient stress. Journal of Experimental Botany, 51, 61-70.
[3]	Cochard H, Ewers F, Tyree M (1994). Water relations of a tropical vine-like bamboo (Rhipidocladum racemiflorum): Root pressures, vulnerability to cavitation and seasonal changes in embolism. Journal of Experimental Botany, 45, 1085-1089.
[4]	Enns L, Canny M, McCully M (2000). An investigation of the role of solutes in the xylem sap and in the xylem paren¬chyma as the source of root pressure. Protoplasma, 211, 183-197.
[5]	Ewers FW, Améglio T, Cochard H, Beaujard F, Martignac M, Vandame M, Bodet C, Cruiziat P (2001). Seasonal variation in xylem pressure of walnut trees: Root and stem pressures. Tree Physiology, 21, 1123-1132.
[6]	Ewers FW, Cochard H, Tyree MT (1997). A survey of root pressures in vines of a tropical lowland forest. Oecologia, 110, 191-196.
[7]	Fan JF, Li Ling, Han YF, Li JR (2002). Establishment of leaf-explant regeneration system of popular 84K. Journal of Northwest Forestry University, 17(2), 33-36. (in Chinese with English abstract)[樊军锋, 李玲, 韩一凡, 李嘉瑞 (2002). 84K杨叶片外植体再生系统的建立. 西北林学院学报, 17(2), 33-36.]
[8]	Fisher JB, Guillermo A, Ewers FW, López-Portillo J (1997). Survey of root pressure in tropical vines and woody spe-cies. International Journal of Plant Sciences, 158, 44-50.
[9]	Henzler T, Waterhouse RN, Smyth AJ, Carvajal M, Cooke DT, Schäffner AR, Steudle E, Clarkson DT (1999). Diurnal variations in hydraulic conductivity and root pressure can be correlated with the expression of putative aquaporins in the roots of Lotus japonicus. Planta, 210, 50-60.
[10]	Holbrook NM, Ahrens ET, Burns MJ, Zwieniecki MA (2001). In vivo observation of cavitation and embolism repair using magnetic resonance imaging. Plant Physiology, 126, 27-31.
[11]	Kamaluddin M, Zwiazek JJ (2001). Metabolic inhibition of root water flow in red-osier dogwood (Cornus stolonifera) seedlings. Journal of Experimental Botany, 52, 739-745.
[12]	Kramer PJ, Boyer JS (1995).Water Relations of Plants and Soils. Academic Press, Kaedinya, Australia.
[13]	Kusakina J, Gould PD, Hall A (2014). A fast circadian clock at high temperatures is a conserved feature across Arabidopsis accessions and likely to be important for vegetative yield. Plant, Cell & Environment, 37, 327-340.
[14]	Li KY, Fan JF, Zhao Z, Zhou YX, Gao JS (2007). Prioritization of the system of regeneration and genetictransformation of Populus 84K. Journal of Northwest A & F University (Natural Science Edition), 35(7), 90-96. (in Chinese with English abstract)[李科友, 樊军锋, 赵忠, 周永学, 高建社(2007). 84K杨再生和遗传转化体系的优化. 西北农林科技大学学报(自然科学版), 35(7), 90-96.]
[15]	Secchi F, Zwieniecki MA (2012). Analysis of xylem sap from functional (nonembolized) and nonfunctional (embolized) vessels of Populus nigra: Chemistry of refilling. Plant Physiology, 160, 955-964.
[16]	Sperry JS, Holbrook NM, Zimmermann MH, Tyree MT (1987). Spring filling of xylem vessels in wild grapevine. Plant Physiology, 83, 414-417.
[17]	Steudle E, Murrmann M, Peterson CA (1993). Transport of water and solutes across maize roots modified by punctur¬ing the endodermis (further evidence for the composite tran¬¬¬sport model of the root). Plant Physiology, 103, 335-349.
[18]	Tyree MT, Sperry JS (1989). Vulnerability of xylem to cavitation and embolism. Annual Review of Plant Biology, 40, 19-38.
[19]	Tyree MT, Yang S, Cruiziat P, Sinclair B (1994). Novel methods of measuring hydraulic conductivity of tree root systems and interpretation using AMAIZED (A maize-root dyn¬¬amic model for water and solute transport). Plant Physiology, 104, 189-199.
[20]	Tyree MT, Zimmermann MH (2002). Xylem Structure and the Ascent of Sap. Springer, Berlin, Germany.
[21]	Wan X, Zwiazek JJ (1999). Mercuric chloride effects on root water transport in aspen seedlings. Plant Physiology, 121, 939-946.
[22]	Wang F, Tian X, Ding Y, Wan X, Tyree MT (2011). A survey of root pressure in 53 Asian species of bamboo. Annals of Forest Science, 68, 783-791.
[23]	Wang SY, Chen QJ, Wang WL, Wang XC, Lu MZ (2005). Cultivation of Populus 84K transferred salt-tolerant genes OsNHX1. Chinese Science Bulletin, 50(2), 140-144. (in Chinese)[王树耀, 陈其军, 王文龙, 王学臣, 卢孟柱 (2005). 转OsNHX1基因耐盐84K杨的培育. 科学通报, 50(2), 140-144.]
[24]	Wegner LH (2014). Root pressure and beyond: Energetically uphill water transport into xylem vessels? Journal of Experimental Botany, 65, 381-393.
[25]	Wilson C, Kramer P (1949). Relation between root respiration and absorption. Plant Physiology, 24, 55-59.
[26]	Wismer WV, Marangoni AG, Yada RY (1995). Low¬tem¬perature sweetening in roots and tubers. Horticultural Reviews, 17, 203-231.
[27]	Yang SJ, Zhang YJ, Sun M, Goldstein G, Cao KF (2012). Rec¬overy of diurnal depression of leaf hydraulic conductance in a subtropical woody bamboo species: Embolism refilling by nocturnal root pressure. Tree Physiology, 32, 414-422.