Abstract
Elevated K fertilization during bedding plant production may reduce irrigation demand and moisture stress during marketing and landscape establishment. Lindhauer (1985) indicated increasing K fertilizer concentration reduced transpirational water loss and decreased the influence of moisture stress on gas exchange for sunflower. The objective of this study was to determine the influence of K nutrition level on gas exchange of salvia (Salvia splendens F. Sellow ‘Bonfire’) during the onset of moisture stress. Seed of salvia were sown on 11 Jan. 1988 and transplanted 14 days later into 500-ml plastic pots containing a 1 peat : 1 perlite (v/ v) medium amended with 1 kg of Micromax (Sierra Chemical Co., Milpitas, Calif.) and 3 kg dolomitic limestone/m. Plants were grown in a glasshouse under long-day conditions [night interruption from 2200 to 0200 HR using incandescent lights providing ≈4 μmol·s ·m photosynthetic photon flux (PPF) at the top of the plant canopies] to extend vegetative growth. Potassium was applied with each watering at 75, 300, or 600 mg K/liter from KCl. Each K solution also contained (in mg·liter) 200 N from NH4NO3 and 25 P from phosphoric acid. Solutions were applied at the rate of 250 ml at each watering to maintain constant root-zone concentrations of nutrients. Treatments were arranged in a randomized complete block design with eight single-plant (eight pots) replicates for each treatment. Plants were irrigated at 0545 HR and placed under supplemental lighting provided with 1000-W high-pressure sodium lamps. Levels of PPF ranged from 605 to 745 μmol·s ·m during gas exchange measurements. Net photosynthesis (Pn), transpiration (E), leaf conductance (gL), and internal CO2 concentration (CI) were obtained using the LI-COR Model 6200 portable photosynthesis system (LI-COR, Lincoln, Neb.). Mean gas analyzer leaf chamber relative humidity, temperature, and CO2 concentration during measurements were 38% ± 7% 27 ± 2C, and 360 ± 27 mg·liter, respectively. Mes-
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