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  • Author or Editor: Paul R. Adler x
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Abstract

Growth retardants have been used to control stem elongation of hydroponic tomato (Lycopersicon esculentum Mill.) transplants. However, the residual effect of chlormequat chloride on vegetative growth reduces yield. Therefore, the recovery rate of transplant growth was compared between treatments that reduce stem elongation (salt stress, thigmic stress, and chlormequat chloride) to determine which treatments had the best combination of a fast growth recovery rate and control of stem elongation. Tomato plants were grown hydroponically during treatment and recovery periods in a recirculating nutrient solution. Although all treatments except thigmic stress initially decreased shoot dry weight, 24 days after treatment (DAT) termination night-salt stress and thigmic stress produced plants with shoot dry weight comparable to controls. Day and 24-hr salt stress and chlormequat chloride-treated plants had shoot dry weights of 40% to 60% of control 24 DAT termination. Plants treated with chlormequat chloride were still growing slower than controls 24 DAT termination. Both night-salt stress and thigmic stress are suitable prospects for use in control of hydroponic tomato transplant vegetative growth. Oscillatory wind stress applied by the sweeping motion of a leaf blower or by brushing plants with a foam rubber mat are potential commercially feasible ways to apply mechanical stress. Chemical names used: 2-chloro-N,N,N-trimethyIethanaminum chloride (chlormequat chloride).

Open Access

Abstract

The addition of chlormequat chloride to tomato (Lycopersicon esculentum Mill.) transplants decreased fruit yield, number, and size. Flowering was accelerated both by chlormequat chloride and by transplanting at a more advanced stage of development. By transplanting a more mature plant without chlormequat chloride, yield was increased over the first 3 weeks of harvest. Although it is difficult to manage a “leggy” transplant, typical of flowering hydroponic tomato transplants grown under low light levels and close spacing, increased yield was sufficient to justify this management practice. Chemical name used: 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat chloride).

Open Access

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

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

Abstract

Single applications of ancymidol at 0.03, 0.12, 0.50, or 1.0 mg/plant were soil applied to asparagus seedlings (Asparagus officinalis L.) 3.5, 5.5, or 7.5 weeks after seeding. Increasing ancymidol rates from 0.03 to 1.0 mg/plant decreased bud number, fern dry weight, but not shoot number at all application times. When ancymidol was applied at 1.0 mg/plant at 3.5 weeks it reduced fleshy root production, but in plants treated at 5.5 to 7.5 weeks, it did not reduce fleshy root production. Increasing ancymidol rates from 0.03 to 1.0 mg/plant reduced the crown dry weight of plants 5.5 weeks and younger. Ancymidol from 0.03 to 1.0 mg/plant applied to 3.5-week-old plants increased the partitioning of dry matter into fern rather than crowns, but delaying application to 7.5 weeks after seeding reversed this relationship suggesting increased carbohydrate storage. Application of ancymidol from 0.03 to 1.0 mg/plant to plants 5.5-weeks-old or younger was considered detrimental to plant growth. Ancymidol at 0.50 mg/plant or less applied to 7.5-week-old plants enhanced the production of a stocky, compact transplant. Chemicals used. Ancymidol: α-cycloprophyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol.

Open Access

Abstract

Increasing the P rates from 0 to 20 ppm increased shoot and crown fresh and dry weight, plant height, and fleshy root and bud production in 10-week-old asparagus (Asparagus officinalis L.) seedlings. Increasing K rates from 0 to 200 ppm decreased the production of fleshy roots relative to buds. Shoot production progressively increased as N rates increased from 100 to 200 ppm in conjunction with P rates increasing from 10 to 20 ppm. The partitioning of dry weight into crowns predominated over that partitioned into shoots in any combination of N rate from 0 to 200 ppm, and P rate from 0 to 20 ppm. With P rates held constant at 0 to 20 ppm, however, increasing the N rates from 0 to 200 ppm tended to reduce the partitioning rate into crowns and enhanced partitioning into the shoots. Nutrient solutions containing at least 20 ppm P and 100 ppm N and K are recommended in vermiculite-perlite-peat media natively low in NPK.

Open Access

Abstract

Sweet basil (Ocimum basilicum L.) plants were grown, until flower buds became visible, in a peat-lite mix and watered daily with a complete nutrient solution with 10 mm N as either NO 3 or NH 4 + . Ammonium decreased plant height and stem plus petiole dry weight. Leaf blade dry weight was not affected by N form. However, the essential oil content was decreased by 28% with NH 4 + , thereby decreasing the essential oil yield per plant. Although NH 4 + decreased the content (nl·g-1 leaf blade dry weight) of linalool and eugenol, their percentage was not altered. Therefore, the changes in total yield of these individual constituents was simply a reflection of less total extractable essential oil. The total amount of the other major constituents in sweet basil, 1,8-cineole, methyl chavicol, and total sesquiterpenes was not affected significantly. While N form did not alter the percentage of monoterpenes and aromatic polypropa-noides, NH 4 + -N increased the total sesquiterpene percentage. Nitrogen form altered the essential oil content and composition of sweet basil and, therefore, should be considered in nutritional studies with aromatic plants.

Open Access

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