14 



MISCELLANEOUS PUBLICATIONS 1251, U.S. DEPT. OF AGRICULTURE 



Iron Solution. — Chelates of iron in ethylenedia- 

 mine tetraacetic acid are commercially available, 

 often as Versene or Sequestrene. Dilute the 

 commercial product to obtain a 5-percent w/v 

 solution. Dissolve 200 ml. of this solution in 

 distilled water and make to 1 liter. This stock 

 solution contains 10,000 p. p.m. of iron. One ml. 

 of stock solution will give an iron concentration 

 of 10 p. p.m. when diluted to 1 liter. 



Micronutrients. — The microelements or trace 

 elements are dissolved together in 1 liter of 

 deionized water to make a stock solution. The 

 microelements should be added to the water in 

 the order listed and each dissolved before the 

 next is added. This prevents precipitates from 

 forming. 



Chemical Formula 



Boric acid H 3 B0 3 



Zinc chloride ZnCl? 



Cuprous chloride CuCl 2 • H 2 



Molybdenum oxide Mo0 3 



Manganese chloride MnCl 2 -4H 2 



Grams 

 per liter 



2.50 

 .50 

 .05 

 .05 

 .50 



Preparation of Nutrient Solution From Stock 

 Solu tions 



The following volumes of the six stock solutions 

 are then individually added to about 500 ml. of 

 deionized water with stirring. After all stock 

 solutions have been added, the nutrient solution 

 is made to 1 liter with deionized water to obtain 

 a full-strength solution. This solution is usually 

 diluted to one-third, one-half, or three-fourths 

 strength. 



Chemical 



Formula Milliliters 



Potassium dihydrogen phosphate.. KH 2 P0 4 1 



Potassium nitrate KN0 3 5 



Calcium nitrate Ca(N0 3 ) 2 5 



Magnesium sulfate MgS0 4 2 



Iron 1 



Micronutrients 1 



TECHNIQUES FOR SPECIFIC PLANTS 



Tables 2 and 3 summarize the methods used 

 for growing several plant species. In table 2 are 

 listed the light, temperature, and humidity re- 

 gimes used for these species when raised in growth 

 chambers and also some growth characteristics 

 obtained under average greenhouse conditions. 

 These characteristics also closely approximate 

 those obtained in growth chambers as listed 

 for each species. In table 3 the germination 

 method, germination period, and nutrient re- 

 quirements are listed. 



For many of the species additional precautions 

 and comments are to be noted if good plant 

 growth is to be insured. These species are listed 

 alphabetically by common name. Some plants 

 are grouped together since their specific growth 

 requirements are nearly identical. For plants 

 not in alphabetical order, see the index. 



Alfalfa. — This species may be propagated 

 vegetatively as well as from seed. Five-cm. stem 

 sections, each bearing one or two trifoliate leaves 

 near the apical end of the cutting, are removed 

 from well-established plants and rooted in moist 

 vermiculite or aerated water for 3 weeks. During 



this period a 12-hour photoperiod with an illumi- 

 nation of 1,000 ft.-c, day-night temperatures 

 of 21° and 16° C, and a relative humidity of 

 75 percent can be used. Flowering can be induced 

 by interrupting the dark cycle for 1 hour near 

 the middle of the night or by increasing the 

 illumination to about 2,200 ft.-c. 1 or 2 weeks 

 after transplanting. 



Barley, Oat, Wheat, and Wild Oat. — The barley 

 variety 'Larker' is susceptible to mildew. This 

 disease may be controlled by lightly dusting 

 the plants with sulfur. It may be desirable to 

 add potassium bicarbonate at a final concentration 

 of 2 X 10 -3 M to the nutrient solution to prevent 

 leaf tipburn of 'Larker' barley. Other barley 

 varieties may not require this treatment. To 

 hasten maturity of barley, oat, wheat, and wild 

 oat grown under short-day conditions, it is neces- 

 sary to interrupt the dark period with light for 

 1 hour near midnight. 



Barnyardgrass, Pigeongrass, and Rice. — When 

 these species are grown in liquid culture, no 

 aeration is required. These grasses may be trans- 

 planted directly into one-third strength solution 



