Search Results

You are looking at 1 - 4 of 4 items for

  • Author or Editor: Paul R. Adler x
Clear All Modify Search
Free access

Paul R. Adler and Gerald E. Wilcox

Two mechanisms that reduce water and salt stress, respectively, are an increase in root hydraulic conductivity (LP) and reduction in Na and Cl absorption and transport to the leaf. NH4 +-N decreased muskmelon LP 55-70% while under 100 mM NaCl stress and 40-50% in the absence of NaCl stress. A decrease in LP increases the rate of water stress development as the transpiration rate increases. Although dry weight decreased about 70%, with NO- 3-N, muskmelon remained healthy green, while with NH+ 4-N they became chlorotic and necrotic with a 100% and 25% increase in leaf blade Na and Cl compared to NO- 3-N, respectively. Further investigation indicated that NH+ 4-N increased muskmelon sensitivity to NaCl through both an increased rate of net Na influx and transport of Na to the leaf. Since Na influx partitioning is controlled by mechanisms K/Na selectivity and exchange across membranes, the NH+ 4-N inhibition of K absorption may impair K/Na exchange mechanisms. Reduced K/Na selectivity or Na efflux are implicated as the source of the increased net Na influx with NH+ 4-N. The importance of K in preventing Na partitioning to the leaf was confined through removal of K from the nutrient solution thereby simulating the NH+ 4-N-induced gradual K depletion in muskmelon. Our work indicates that at a given level of water or NaCl stress, NO- 3-N reduces the level of stress experienced by muskmelon through increasing LP and reducing the net rate of Na influx and transport to the sensitive leaf blade. This avoidance mechanism should enable muskmelon plants fertilized with NO- 3-N to tolerate greater levels of stress.

Free access

Paul R. Adler and Gerald E. Wilcox

Two mechanisms that reduce water and salt stress, respectively, are an increase in root hydraulic conductivity (LP) and reduction in Na and Cl absorption and transport to the leaf. NH4 +-N decreased muskmelon LP 55-70% while under 100 mM NaCl stress and 40-50% in the absence of NaCl stress. A decrease in LP increases the rate of water stress development as the transpiration rate increases. Although dry weight decreased about 70%, with NO- 3-N, muskmelon remained healthy green, while with NH+ 4-N they became chlorotic and necrotic with a 100% and 25% increase in leaf blade Na and Cl compared to NO- 3-N, respectively. Further investigation indicated that NH+ 4-N increased muskmelon sensitivity to NaCl through both an increased rate of net Na influx and transport of Na to the leaf. Since Na influx partitioning is controlled by mechanisms K/Na selectivity and exchange across membranes, the NH+ 4-N inhibition of K absorption may impair K/Na exchange mechanisms. Reduced K/Na selectivity or Na efflux are implicated as the source of the increased net Na influx with NH+ 4-N. The importance of K in preventing Na partitioning to the leaf was confined through removal of K from the nutrient solution thereby simulating the NH+ 4-N-induced gradual K depletion in muskmelon. Our work indicates that at a given level of water or NaCl stress, NO- 3-N reduces the level of stress experienced by muskmelon through increasing LP and reducing the net rate of Na influx and transport to the sensitive leaf blade. This avoidance mechanism should enable muskmelon plants fertilized with NO- 3-N to tolerate greater levels of stress.

Free access

Gerald E. Wilcox, Paul R. Adler and Mohamad Errebhi

A study was made to investigate the effects of liming and N source fertilization on soil acidity, nutrient uptake an yield of muskmelon on a Princeton loamy-sand (fine sandy, mixed, mesic, type Hapludalf) at Southwest Purdue Agricultural Center, Vincennes, IN. The experiment consisted of lime and no lime treatments with five N treatments of 0 N, 50 kg·ha-1 N as urea and 100 kg·ha-1 N as urea, NH4NO3, and (NH4) SO4. The unlimed soil tested pH 4.6, 4.2 and 4.1 and the limed soil was pH 5.5, 5.6 and 5.2 with 100 kg N·ha-1 as urea, NH4NO3 and (NH4) SO4, respectively. With NH4NO3 the NO3-N declined from 268 ppm on 6/1 to 64 ppm on 7/7 in the saturation extract (SE). Highest NH4-N was from (NH4)2SO4 followed by NH3NO4 and urea. The NH4-N concentration from (NH4)2SO4 in the SE decreased from 152 ppm to 19 ppm during the season on unlimited soil and from 56 ppm to 8 in the SE decreased from 152 ppm on limed soil. Symptoms of Mn toxicity in the leaves became apparent on unlimed plots 7 weeks after transplanting. As the rate of N increased in the range of 0, 50 and 100 kg·ha-1 from urea the Mn contents were 372,459 and 607 ppm respectively. The muskmelon fruit yield increase due to 100 kg N·ha-1 was 13279 kg·ha-1, 12161 kg·ha-1 and 8502 kg·ha-1 for ureas, NH4NO3 and (NH4)2SO4 respectively.

Free access

Paul R. Adler, Jayson K. Harper, Fumiomi Takeda, Edward M. Wade and Steven T. Summerfelt