Growth and Physiological Changes of <i>Juglans Regia</i> L. Seedlings under Nitrogen Deficiency Stress

Abstract

Walnut (Juglans regia L.) seedlings were treated with varying degrees of nitrogen (N) deficiency. The effects of N deficiency on the growth and physiology of walnut seedlings were investigated, and the adaptability and mechanism of walnut seedlings to the N-deficient environment in barren soil were explored. The purpose is to provide a scientific basis for the breeding and fertilization management of walnut varieties with high resistance and to promote the healthy and sustainable development of the walnut industry. The results showed that: (1) Under N-deficient conditions, the aboveground biomass, root biomass, chlorophyll a, chlorophyll b, and carotenoid contents of walnut seedlings were clearly lower than those of the control group, and generally diminished more obviously with the aggravation of N deficiency and the prolongation of treatment time; (2) The net photosynthetic rate, stomatal conductance, and transpiration rate of walnut seedlings in the control (CK) group were the highest overall across all N deficiency, followed by the moderate N deficiency (MN) group and the lowest in the severe N deficiency (SN) group; (3) Under N deficiency, the contents of indole-3-acetic acid (IAA), cytokinin (CTK), and abscisic acid (ABA) in the walnut seedlings increased significantly, and the contents in SN group were the highest. With processing time extended, the contents of IAA and ABA in walnut seedlings under N deficiency increased continuously, while CTK content increased rapidly within 30 d, and then declined speedily after 30 d. In addition, the ethylene content of walnut seedlings under N deficiency stress gradually increased within 30 d, and then dropped dramatically after 30 d, which was generally lower than that of the CK group; (4) During the whole experiment, the contents of putrescine (Put), spermidine (Spd), and spermine (Spm) in walnut seedlings under N deficiency stress were lower than those in the CK group in general. This indicated that the accumulation of Put, Spd, and Spm in leaves was inhibited under N deficiency; (5) Compared with the CK group, the root activity

Effect of Dopamine on Growth, Some Biochemical Attributes, and the Yield of Crisphead Lettuce under Nitrogen Deficiency

“…Nitrogen, along with carbon, represents the most important nutrient for leafy crop growth and productivity, as well as constituting the majority of plant biomass [35]. So, under ND, plant growth and productivity were dramatically reduced, as reported previously [3,[5][6][7]. This decrease is frequently attributed to that ND-persuaded malady in Along with the correlation exploration, the relationship between the parameters deliberated and DA foliar spraying for ND-stressed crisphead lettuce plants was examined using the heatmap.…”

“…Nitrogen, along with carbon, represents the most important nutrient for leafy crop growth and productivity, as well as constituting the majority of plant biomass [35]. So, under ND, plant growth and productivity were dramatically reduced, as reported previously [3,[5][6][7]. This decrease is frequently attributed to that ND-persuaded malady in almost physiomolecular changes, i.e., hindrance of water and photo-assimilates translocation; destruction of plant photosynthetic efficiency and damage of ATP assimilation prerequisite for plant establishment [5,7,36]; hampered ion uptake and similarly, the extreme ROS creation [3,8].…”

“…In the present investigation, chlorophyll concentration significantly decreased under ND; however, exogenous DA treatment clearly reversed these negative effects. These outcomes were approved by former studies [5,6,34,36]. The declining impacts of ND on chlorophyll levels may be a result of the switch-off chlorophyll assimilation genes, resulting in the diminishing of ALA synthesis pathways and chlorophyll decline [7,16,36].…”

“…Alternatively, excessive N fertilizer supplementation is expensive and hastens the deprivation of the environment and human health [2,4]. Due to the fact that N is elaborate in most plant metabolic pathways, nitrogen deficiency (ND) is able to influence photo-assimilation allocation arrays, alter serious physio-biochemical pathways and molecular reactions, plant establishment, stunted growth, and reduced flowering and seed setting [1,5,6]. Since more than half of the N in leaves is devoted to chloroplasts, ND also accelerates leaf chlorosis and experiences a great reduction in photosynthetic rates that diminish plant development and marketable values of leafy plants [5][6][7].…”

“…Due to the fact that N is elaborate in most plant metabolic pathways, nitrogen deficiency (ND) is able to influence photo-assimilation allocation arrays, alter serious physio-biochemical pathways and molecular reactions, plant establishment, stunted growth, and reduced flowering and seed setting [1,5,6]. Since more than half of the N in leaves is devoted to chloroplasts, ND also accelerates leaf chlorosis and experiences a great reduction in photosynthetic rates that diminish plant development and marketable values of leafy plants [5][6][7]. More importantly, ND accelerates the over-production of reactive oxygen species (ROS) that causes ubiquitous cellular destruction and dysfunction of numerous physio-molecular responses [7,8].…”