Gibberellin Is Involved in Inhibition of Cucumber Growth and Nitrogen Uptake at Suboptimal Root-Zone Temperatures

Abstract

Suboptimal temperature stress often causes heavy yield losses of vegetables by suppressing plant growth during winter and early spring. Gibberellin acid (GA) has been reported to be involved in plant growth and acquisition of mineral nutrients. However, no studies have evaluated the role of GA in the regulation of growth and nutrient acquisition by vegetables under conditions of suboptimal temperatures in greenhouse. Here, we investigated the roles of GA in the regulation of growth and nitrate acquisition of cucumber (Cucumis sativus L.) plants under conditions of short-term suboptimal root-zone temperatures (Tr). Exposure of cucumber seedlings to a Tr of 16°C led to a significant reduction in root growth, and this inhibitory effect was reversed by exogenous application of GA. Expression patterns of several genes encoding key enzymes in GA metabolism were altered by suboptimal Tr treatment, and endogenous GA concentrations in cucumber roots were significantly reduced by exposure of cucumber plants to 16°C Tr, suggesting that inhibition of root growth by suboptimal Tr may result from disruption of endogenous GA homeostasis. To further explore the mechanism underlying the GA-dependent cucumber growth under suboptimal Tr, we studied the effect of suboptimal Tr and GA on nitrate uptake, and found that exposure of cucumber seedlings to 16°C Tr led to a significant reduction in nitrate uptake rate, and exogenous application GA can alleviate the down-regulation by up regulating the expression of genes associated with nitrate uptake. Finally, we demonstrated that N accumulation in cucumber seedlings under suboptimal Tr conditions was improved by exogenous application of GA due probably to both enhanced root growth and nitrate absorption activity. These results indicate that a reduction in endogenous GA concentrations in roots due to down-regulation of GA biosynthesis at transcriptional level may be a key event to underpin the suboptimal Tr-induced inhibition of root growth and nitrate uptake. These findings may have important practical implications in effective mitigation of suboptimal temperature-induced vegetable loss under greenhouse conditions.

24-Epibrassinolide Ameliorates Endogenous Hormone Levels to Enhance Low-Temperature Stress Tolerance in Cucumber Seedlings

“…Auxin is produced in young leaves and is involved in many growth and developmental processes, including cell division, phototropism, gravitropism, and phytohormone regulation to increase stress tolerance [ 26 ]. Gibberellins (GAs) are produced in roots and play important roles in growth, promoting cell division, increasing nitrogen metabolism, and promoting stem and root elongation, as well as reducing stress effects [ 27 ]. Regulation by phytohormones is very important for plant growth, and each hormone plays a dynamic role in the induction of stress tolerance [ 8 ].…”

“…Cucumber ( Cucumis sativus ) is an economically important crop worldwide. It is a summer crop with an optimum growth temperature of 26 °C/18 °C day/night [ 27 ]. Cucumber can grow during the winter in solar greenhouses, where exposure to low temperatures is the main cause of reduced growth and yield [ 10 ].…”

5-Aminolevulinic Acid Improves Nutrient Uptake and Endogenous Hormone Accumulation, Enhancing Low-Temperature Stress Tolerance in Cucumbers

“…The optimum growth temperature for cucumber is between 24 and 28 °C [ 9 , 20 ]. Temperatures above 30 °C or below 12 °C cause significant reduction in growth [ 9 , 10 ].…”

Exogenous glycine inhibits root elongation and reduces nitrate-N uptake in pak choi (Brassica campestris ssp. Chinensis L.)

“…Studies typically quantify the effect of exogenous Gly on the NO 3 - content and other physiological responses of leafy vegetables grown in hydroponic culture [ 4 , 5 , 27 , 40 , 41 ]. Furthermore, hydroponic conditions has been employed to study root morphology and NO 3 - -N uptake in Chinese cabbage [ 42 ], cucumber [ 43 ] and tomato [ 44 ], as well as the role of ethylene in the modulation of root length in wheat [ 40 ]. Therefore, we used a hydroponic system to assess the effect of exogenous Gly on the root morphology and NO 3 - -N uptake and verify the role of ethylene in these processes in pak choi.…”