The purpose of this report is to explain some of these Early growth of the com seedling was studied in relaenergy relationships involved in the germinating seed. tion to its dependence on energy from endosperm and early photosynthetic tissue. ~easurc:ments ,..ere made of EXPERIMENTAL PROCEDURE (1) endosperm utilization rate of seedlings grown in light and dark; (2) growth and leaf area of seedlings as affectEndosperm Utilization and Growth of Com ed by partial endosperm removal; and (J) photosynthesis (P), respiration (R), and .':CO, up~ake of seedlings as Hybrid field com seed was selected because of its large size. affected by endosperm eXCISion at different ages. Endo'Ve determined endosperm utilization and growth of corn seedsperm utilization and growth rates were similar in l~ght lings in the light and in the dark in t\\-O experiments. In the and dark unt.il the two.leaf stage 10 days after germmafirst experiment, 28 \..eighed lots of 10 seeds each were germintion. Regression of root and shoot growth on age was ated in the light and 28 similar lots in the dark. Seedlings were 15.4 mg/day and of root and sh~t growth on endosperm grown on plexiglass slant boards covered \vith \vet blotter paper. ,,-eight loss was .65 mg/mg. Partial removal of the endoSeeds from each lot \vere placed in a line 7.6 cm from the top sperm at seeding resulted in decreased growth of roots of the board and held in place by wetted tissue paper. The and shoots and indecreased leaf area per seedling. Apseeds ,vere then covered "ith blotter paper, \vhich remained parent P was uegati~'e at 9 days of age and was greatest \"et from \"ater mo\ing up the boards from trays set at their for seedlings "ith endosperm excised. Apparent P was bases, The plants \"ere grown in a growth chamber with a positive and similar at days 11, 12, and 13 for seedlings temperature of 21,8 :t: 1 C. a light intensity of 20,000 lux and "ith endosperm e.xcised and was positive, and increased a photoperiod of 15 hours. For the dark treatment. slant boards from day 11 to day 13 for seedlings with endosperm. ,vere covered with a large cardboard box. Temperature within Energy obtained from CO, fixation was not equivalent the box was assumed to be equal to that of the growth chamber. to that supplied by the endosperm until the lOth day. At Two seed lots ,vere sampled from both light and dark treat. this time seedlings had two fully emerged leaves. Absorpments during a 22-day period at 2-day intervals from germination of 1'CO, ',-as similar for seedlings \vith and without tion. At each sampling date, seedlings ,vere separated into endospetm, and increased ,,'ith age as a result of increased roots, shoots, endosperm, and scutellum. These components leaf area and increasl'{l absorption per unit of leaf area. \vere placed into ,veighing bottles, oven-dried. and weighed. Endosperm removal resulted in greater translocation of The second study \vas similar to the first, except that sam. 1'CO. to seedling roots. plillg \vas at I-day intervals from the 5th throllgh the 16th day, . .. and the sclltellum ,''as weighed \vith the endosperm. Additional inde_'\: words: PhotosynthesIS, Respiration, Gennination energ,.. . Photosynthesis and Respiration Corn seedlings \..ere gro\vn on slant boards in the light under S OURCES of energy for early growth of a grass seedthe experimental conditions previously described. From the 8th ling are: first, the endosperm; second, the endoto the 12th day, the largest and most unifo,rm seedlings w.ere Sperm and ne" leaf material' and third new leaf mas~lected and paired for study of photosynthetic, (P) and resplra. . . , h tlon (R) rates. From one member of each pair the endosperm tenal after depletion of the endospe~n. T ese stages \vas excised \vith a razor blade. Each seedling was then placed of energy dependence have been denned by Whalley. in a 65-cc bottle half-filled with a complete nutrient solution, '~ McKell, and G;reen (6) as hete;otrophic, transitional, and ,vas hel~ in place by cotton wedged between t~e seedling " 'j, and autotro ph1c stages of seedl1ng develo p ment. The and the neck of the b?ttle. After 24 ~ours of seed~mg growth, . .' ch P and R of leaf matenal \vere determmed. Just prior to deterrol: of the en.dosperm 1.11 g~rm~natIon and the. anges minations, strips of bees,vax were wedged bet\veen the seedling whIch occur In the redIstnbut10n of metabol1tes have and th bottle neck, to seal off the top from the root environbeen thoroughly studied b)' other workers, particularly mel~t. T~us, CO, exchange determinations .\,-ere made on the I .n corn (2 3) Little is known however concerning top. only, bllt as affected by the absence or presence of endo1 .'.., " sperm. Measurements of P and R were made m a leaf chamber the relative contrIbutions of endosperm and ne,v leaf at 21.8 C, and 30% relative humidity. Light energy during P material to the total energy of the plant. ,vas 0,33 cal/cm'/min pro,ided by three 500-\vatt photo flood In P revious studies on the effect of tem p erature fila~ent !ight~. Measurements of P an.d dark R were made by . . . passmg air \Vlth a CO, content of 325 ppm through the leaf stress on seedling gro~.th, rate of endosperm utIl1zachamber and measuring the increase or decrease in CO. of air tion was used as a criterion in delineating the stage coming out of the leaf chamber with an infra-red gas analyzer. of seedling de,elopment. Green shoots developed 10llO' Flo\v of air through the chamber \vas controlled at rates of from bef?re the en~osper~ '''as completely. utilized (1, .4f ~r~e;t~iters per min, depending on the amount of leaf material ThIS observauon raIsed several questions concermng At each seedling age, P and R measurements were made on energy relationships. What is the importance of endothree to sLx replications of seedlings ,vith or \\ithout endosperm, I spenn once the green shoot has emerged? Is its rate of ~llm~ers ,of seed~ings 'per replication ,vere ,~ec.reased ~it? age t'l. t'o ffected by the Presence of the green shoot and size m order to keep air flow rates \'Ithm .the lImits of u 1 1Za 1 n.a .. . Ollr flo\\.meters, and ,vere 5. 3, 3, 2, and 1. respectively for ages and what IS the contrIbutIon of the latter to the seedof 9, 1°, 11, 12, and 13 days. Follo,ving each determination. ling while energy is still available from the endospenn? leaves \vere clipped at the surface of the \vax on each bottle. traced on paper, oven-dried. and ,veighed. Rolled or partially I rolled leaves \vere not unrolled for tracings of leaf area, Leaf 1 Contribution from theCrops Research Division, Agricultural tracings were cut out and \veighed. The ratio of area to ,veight Research Service, U. S. Department of ,\griculturc and the Monof paper ,..as llscd to calculate leaf areas. tana Agricultural Experiment S~ation. Publis~ed with approval , of the director as Paper No. 98:). Journal Series, Montana Agr. 14COZ Labellmg Exp. Sta. Received July II, 1969. . . . . , , :\gronomist, Crops Research DIvIsion: -,\~S, USDA and Seedlmgs of S, 9, .'°, II. and 12 days o~ age, \vlth and lVlthout gradllate assistant, Dept. of Botany and ;\Ilcroblology, Montana cndosperm. ,vere glv~n ~'C~. to det.ermme the effe~t of endoState University. Bozeman, ~Iont. 59715. sperm removal on distrIbution of fIXed CO.. Seedlmg growth