Nitrate uptake of seedling and mature kentucky bluegrass plants

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Understanding the relationship between seedling nitrate uptake rate (NUR) and mature plant NUR will benefit the selection of turfgrass cultivars for high NUR. Seedling NUR as affected by initial mowing is particularly important during turfgrass establishment. The primary objectives of this study were to determine NUR of individual Kentucky bluegrass (Poa pratensis L.) seedlings, to correlate seedling morphological characteristics with NUR, and to ascertain the relationship between seedling NUR and mature plant NUR. Thirty days after seeding, roots of seedlings were placed individually in a polystyrene cup filled with 2 mL of a nutrient solution containing 0.6 mM nitrate, which was replaced at 24-h intervals for 20 d. After the total leaf and total root length and area were determined, each seedling was planted in silica sand and maintained as a miniature turf for five additional months before NUR was determined in a 130-mL growth vessel. Seedling NUR was 10 to 60 nmol h -1 per seedling, decreased sharply to <10 nmol h-1 per seedling following the first clipping to remove 1/3 of the leaf blades by length. One week after the first clipping, NUR gradually increased to levels above 10 nmol h-1 per seedling. After seedlings were placed in deionized water for 24 h, NUR during the subsequent 24 h was stimulated, but the magnitude of stimulation differed among cultivars. We found significant among-cultivar and within-cultivar differences in seedling NUR, and significant and positive correlations between seedling NUR and seedling size. At the whole plant level, the correlation between seedling NUR and mature plant NUR was positive but generally not significant at P = 0.05.

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Crop Science