Especially impressive is the fact that the chemical in a test tube 

 has not upset any of the deductions about it, formed from observing the 

 reactions of growing plants and their seed. 



A Pigment Detector's Report: Phytochrome Here 



A sensitive instrument for measuring small amounts of pigment 

 made it possible to locate phytochrome's presence and to report whether 

 it was in active or inhibiting form. This single-beam spectrophotometer 

 was devised by Karl Norris, research engineer of the USDA Agricultural 

 Marketing Service, for investigations of plant color and market quality. 

 The instrument scans a selected region of the spectrum, casting light of 

 changing wave length on a plant or tissue. At each wave length, it measures 

 the light transmitted through the dense material, registering the absorption 

 by ink markings on a chart. 



Using this instrument, the research team applied successive red and 

 far red to 6-day-old corn seedlings and got direct evidence of phytochrome's 

 presence and reverses. Seedlings for these tests were grown in the dark 

 to prevent their developing green chlorophyll, which reacts to red and 

 might interfere with the evidence. The young plants ow^n seed gave them 

 food for 6 days of growth with no light. 



Ground-up tissue from corn plants and liquid extract from the tissue 

 were tested also. And to locate phytochronne in varied kinds of plants and 

 at different stages, the instrunnent was directed on test materials of 20 

 plant species. These included the stems and flowers of other grasses 

 besides corn, spinach leaves, cauliflower's white florets, and fruits of 

 avocado and zucchini squash. 



A Rapid Detector's Assay Report 



A second instrument built by AMS engineers made it possible to 

 assay naore exactly and quickly the tiny amounts of phytochrome dis- 

 tributed in plant tissues. This dual-monochromator spectrophotometer 

 has much nnore sensitivity than the single-beam instrument and it gives 

 wanted information instantly, without the mathematical computation nec- 

 essary to relate the data on wave length effects when the single -beam 

 instrument is used. In figure 3 a bean seedling is in position for a phyto- 

 chrome assay. 



Assays with this instrument indicate that phytochrome announts at 

 the most to a millionth of a plant's total weight. Young corn seedlings 

 contain a relative abundance. 



Phytochrome is far from evenly distributed. In 6-day corn seedlings, 

 it was found most concentrated in two areas: (1) In the higher part of 

 the actively lengthening first internode (the stem section between joints, 

 first springing up fronn the seed); and (2) in the first developing leaf, 

 folded sheathlike around its stem. 



Phytochrome in the Open 



Knowing where phytochronne is and how much of it to expect at best, 

 the research team applied fractioning processes to corn plant tissues. 



12 



