Effect of Phosphorus Deficiency on Root Growth and Root Exudates of Cucurbita pepo 'Luoren'

As a special germplasm with a soft seed coat, Cucurbita pepo 'Luoren' has been planted widely in the north of China. It was bred from a mutant of Cucurbita pepo L. The seed length, width, thickness and 1000-seed weight of Cucurbita pepo 'Luoren' were found to be 14.5 +/- 0.7 mm, 8.1 +/- 0.4 mm, 2.3 +/- 0.2 mm, and 130.5 +/- 10.5 g, respectively. Phosphorus deficiency hindered the productivity of Cucurbita pepo 'Luoren'. To probe the morphological and physiological responses of C. pepo 'Luoren' in response to phosphorus deficiency, the biomass, root morphological characters and root exudates were determined by using nutrient solution approach in the greenhouse. The results showed that on the 21 days after phosphorus deficiency, the root and shoot biomass of C. pepo 'Luoren' were all significantly decreased, root/shoot ratio and root tips increased, P uptake efficiency and P reallocation efficiency decreased and P utilization efficiency increased significantly. Citrate exudation by C. pepo 'Luoren' after phosphorus deficiency was as much as twice higher as in normal phosphorus status, and citrate was found in the specific organic acid exudates by C. pepo 'Luoren'. On the 21 days after phosphorus deficiency, root exudates of C. pepo 'Luoren' contained more components than those in normal phosphorus status. Two-, four-Ditertbutyl phenol, Butylated hydroxytoluene, 1, 2-Benzenedicarboxylic acid, butyl 2-methylpropyl ester, Z-8-Hexadecene and Hexadecanamide were special components in C. pepo 'Luoren' exudates under phosphorus deficiency.