Water-deficit treatment followed by re-watering stimulates seminal root growth associated with hormone balance and photosynthesis in wheat (Triticum aestivum L.) seedlings

Abstract

Elucidating the growth responses of roots to water status will reveal physiological mechanisms underlying drought tolerance and water conservation in plants. Hydroponic experiments were conducted using two winter wheat cultivars, Wangshuibai (drought-sensitive) and Luohan 7 (drought-tolerant), and a water deficit was induced using a 20 % (m/v) aqueous solution of polyethylene glycol 6000 (-0.6 MPa). The lack of water significantly reduced the plant dry weight, leaf area, total root length (TRL) and surface area in seminal (SRs) and nodal roots (NRs), but the effects were less pronounced in Luohan 7 than in Wangshuibai. After re-watering, leaf area, TRL and surface area of Luohan 7 increased significantly, as compared to the controls, due to rapid compensatory growth of SRs, while those of Wangshuibai were still significantly reduced. Under water-deficit conditions, the concentrations of indole-3-acetic acid (IAA) and cytokinin (CTK) and their ratio (IAA/CTK) in SRs and NRs of both cultivars were significantly lower than those of controls, but increased after re-watering. However, Luohan 7 showed significantly increases in IAA/CTK of SRs as compared to the control. Net photosynthetic rate was much lower during water deficit in both cultivars, but it was enhanced significantly after re-watering, especially for Luohan 7. Moreover, sucrose content was significantly increased in leaves while reduced in roots under water-deficit conditions. After re-watering, sucrose content in leaves of both cultivars and in roots of Wangshuibai was severely reduced, while the values in roots of Luohan 7 were significantly increased as compared to the control. These results indicate that the drought-tolerant cultivar has a greater ability to maintain plant growth under water deficit and greater compensatory growth in SRs associated with higher IAA/CTK and photosynthetic products supply after re-watering.

Prolonged drying cycles stimulate ABA accumulation in Citrus macrophylla seedlings exposed to partial rootzone drying

“…Thus root growth was stimulated in the irrigated pot of PRD-Fixed plants (Wang et al, 2005) and in response to alternating wetting and drying parts of the rootzone in PRD-3 plants (Mingo et al, 2004). Although understanding the physiological mechanisms determining root growth dynamics following soil moisture fluctuations was beyond the scope of this study, changes in root phytohormone (auxin, cytokinin) concentrations have been implicated (Han et al, 2015).…”

Higher Ammonium Transamination Capacity Can Alleviate Glutamate Inhibition on Winter Wheat (Triticum aestivum L.) Root Growth under High Ammonium Stress

“…Several previous studies have reported that the root vascular tissues differentiation and regeneration were induced and controlled by polar IAA movement from the young leaves to the root tips [ 38 , 40 ]. Moreover, higher IAA concentration in roots promoting a more active sucrose metabolism was observed in a wheat cultivar Luohan 7 [ 41 ]. So, some report found that the carbohydrates transport could be regulated by IAA distribution in plants and increased IAA in roots could promote sucrose transport from leaves to roots.…”

Physiological and biochemical changes during drought and recovery periods at tillering and jointing stages in wheat (Triticum aestivum L.)

“…The experiment was carried out under a rain exclusion shelter during the growing seasons of 2014–2015 and 2015–2016 at Pailou Experimental Station of Nanjing Agricultural University (32 ◦ 04′N, 118 ◦ 76′E), China. The two most widely grown wheat cultivars in the region (lower Yangtze River Basin), namely Luhan7 (drought-tolerant) and Yuangmai16 (drought-sensitive) were used as experimental materials 2 . These cultivars show similar phenology and yield potentials under optimum field conditions.…”

“…Thus, identifying key physiological limitations to productivity under drought and mechanisms of crop tolerance to water deficit stress will be important for improving yield stability in a changing climate. Moreover, limited genetic diversity within important crop species coupled with ecological constraints to productivity need to be overcome in-order to adapt crops to episodic drought events in the future 2 , 3 . The ability of plants to maintain physiological functions at low plant water status and recover quickly once the stress is removed will be important for ensuring sustainable crop production under intermittent drought events 4 .…”