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Bell pepper (Capsicum annuum L.) plants were sprayed at full bloom with paclobutrazol (50 and 100 mg·liter–1), uniconazole (20 and 50 mg·liter–1), or mefluidide (20 and 50 mg·liter–1). Mature-green and red fruit were harvested 4 and 8 weeks after spraying, respectively. Paclobutrazol and uniconazole, but not mefluidide, affected plant growth and fruit morphology. All three growth regulators alleviated chilling injury that developed on green and red peppers after 28 days at 2C. Potassium leakage was lower from tissue disks, and weight loss less, from treated fruit than from control fruit. Ethylene and CO2 production at 20C were similar in control and paclobutrazol-treated fruit after 28 days at 2C. These results are consistent with previous findings that showed these growth regulators are able to increase tolerance to low temperatures in whole plants. Chemical names used: N-[2,4-dimethyl-5-trifluoromethyl sulfonyl amino phenyl acetamide] (mefluidide); (2RS, 3RS) 1-(4-chlorophenyl)-4,4 dimethyl-2-(1,2,4-triazol-1-yl)-pentan-3-ol (paclobutrazol); (E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4 triazol-1-yl)-pentan-3-ol (uniconazole).
We investigated the effects of N nutrition on growth and carbohydrate partitioning of pepper (Capsicum annuum L., cv. Maor) seedlings in the greenhouse and on their subsequent recovery and development after transplanting. Seedlings received 0, 30, 100, or 200 mg N/liter for 14 days, after which they were transplanted and received 100 mg N/liter. Nitrogen levels below 100 mg·liter−1 inhibited shoot growth and leaf chlorophyll content; both were severely inhibited in the absence of supplemental N. Root growth had a negative relation with N supply; an enhanced root: shoot ratio was observed under low-N regimes. On a unit-leaf-area basis, CO2 fixation was not affected when N was present; however, it was greatly inhibited in the absence of N. Changes in the leaf starch and soluble sugar concentrations occurred as a function of N supply and leaf age. In the roots, low N led to lower sucrose and higher levels of hexose and starch. More sucrose was transported and accumulated into leaf veins of low-N tissue. Exogenously supplied 14C-labeled sucrose was rapidly converted into starch in the low-N tissue. Seedlings that received 100 mg N/liter had the highest post-transplant growth rate and flowered earlier. Carbohydrate status of young pepper seedlings influenced their post-transplant recovery. Optimal N supply is essential for full recovery and development of transplants.