Plant Physiology - Effect of Temperature upon Translocation … · The Effect of Temperature upon Translocation of C24 in Sugarcane Constance E. Hartt Physiology and Biochemistry

The Effect of Temperature upon Translocation of C24 in SugarcaneConstance E. Hartt

Physiology and Biochemistry Department, Experiment Station, Hawaiian Sugar Planters' Association, Honolulu

The author's work with translocation of ra(lioactive photosynthate in sugarcane plants grown undernormal conditions of climate and nutrition has beenreported previously (13). The amounts and ratesof translocation in sugarcane are affected by thetemperature of the air or roots, by light, by moisture,an(l by deficiencies in potassium, nitrogen, or phos-phorus. Our investigations were undertaken bothfor practical reasons an(l in an atteml)t to elucidatethe factors responsible for energizing the transloca-tory process. Both temperature and light are closelyinvolved (11, 12). The results front studies of in-tensity and quality of light which suggest a photocon-trol theory of translocation (9 ) will be reporte lShortly. This paper deals with the effects of temnpera-ture of air and roots, regulated separately, upon thetranslocati on of C'4 photosynthate, already reportedbriefly (2,4, 9, 10), and with the direct effect of airtemperature upon translocation in detached blades.The experiments were conducted front 1956 to 1963.

Methods

The variety of sugarcane used, H 37-1933, wxasthe samve as previously reportedly (13).

The plants were grown singly in 8-liter crocks ina complete nutrient solution. To regulate root tem-perature, the crocks were set in troughs of waterwith the temperature of the water thermostaticallycontrolled. Air temperatures were not maintainedlat uniform levels throughout the day, because thatis not the normal way of growing sugarcane. In-stead, the daily range in temperature of 1 glasshousewas higher than outdoors, and the daily range intemperature of the other glasshouse was lower thanoutdoors (fig 1). The air temperature of the con-trol plants was the normal outdoor temperature atthis station. The air in the glasshouse was contin-uously changed; the CO2 content of the air withinthe houses was equal to that of the outside air. Mleth-ocls of application of C1402, harvesting, sampling, andcounting, were the same as reported previously (13).Briefly, equal aliquots of previously prepared C140.2were supplied to a portion of a single blade, eitherthe upper half enclosed in a 1-liter graduate or acentral portion enclosed in a specially constructedchamber made of wood and plastic. The duration of

1 Received June 22, 1964.2 Published with the approval of the Director as Paper

No. 145 of the Journal Series of the Experiment StationHawaiian Sugar Planters' Association.

exposure was 5 to 15 minutes after which the chamberwas remove(l and translocation continued in air.Further details of the methods are descril)e(l in thelegencls. All translocation tests were carried outWith high light intensities (full sun) except as noted.

The directt effect of temperature upon transloca-tion was studied at 5 to 60 and 21 to 230 by the (le-tached blade method (11).

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FIG. 1. Climate houses for growing sugarcane plantswith air and root temperatures regulated separately. Airtemperature in the house at the left was maintained bhlo\xoutdoor temperature; center, above outdoor temperature.Outdoor control plants were at the right. The shed he-hind the outdoor controls, for the purpose of darkeningthe plants, was not used in these temperature tests.

Results7Tcmnpcrahtrc of Air; Plants Growni (a1(1 7icse/d

linder EXrpcrinicn0tal Coniditions. Translocation wasmeasured in a, plant from the control series which hadbeen grown at the outdoor air temperature at thisstation and in a plant grown in the cold house withthe air averaging 8" lower than outdoor air, thisaverage temperature being for the entire growthperiod of the plants. Figure 2 shows the tempera-tures during the experimental period of feeding theC1402, and subsequent translocation; figure 3 showsthe disappearance of radioactivity from the fed blade(considered to be translocation). Translocation inboth plants was most rapid the first 6 hours, andleveled off after 30 hours. The plant in the cold airalways retained a. higher percentage of radlioactivitvin the fed blade than did the control, indicating lesstranslocation in cold air than in warnmer air.

Copyright (c) 2020 American Society of Plant Biologists. All rights reserved.

HARTT-TEMPERATURE AND TRANSLOCATION IN SUGARCANE

The temperatures from 8 AM to 4 PM the first daywere averaged. The Q10 for translocation out of thefed blade, when calculated for either 13 to 230 or for15 to 250, was 1.2.

30*13Z OUTDOORSX-x IN THE COLD HOUSE

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FZIG. 2. Air temperatures in the cold house and out-dloors, in 2-hr averages, during the experimental periodof feeding the C1402 and translocation (fig 3).

100

90

80

70

60

50

40

30

20

10

0M N M N M N M NJan.24 Jan. 25 Jan. 26 Jan. 27

DAYS(M -Midnight; N -Noon)

FIG. 3. Effect of air and root temperature, regulatedseparately, upon translocation of C14 photosynthate fromthe fed blade. C1402 (225 lac) was fed to the upperportion of blade 5 enclosed in a 1-liter graduate, the bladepassing through a split cork, for 15 min in sunlight.Immediately after removing the graduate, the initialpunch samples were taken near the apex of the fed part.The samples were dried, weighed, ground in a mortarwith alcohol, plated, and the radioactivity recorded andplotted as 1009o. Subsequent samples, taken below thefirst, at 6 hr, 24 hr, and twice daily for a total of 4 days,were treated the same way and their radioactivity plottedas per cent of the initial samples.

The distribution of radiocarbon in the plants 6days after feeding (fig 4) showed that cold air de-creased total translocation from the fed leaf and jointand decreased translocation up the stem. Since theroots were at a higher temperature than the air, theywere able to grow better than the tops and couldattract and retain a higher percentage of the radio-active translocate than did the roots of the controlplant.

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FIG;. 4. Effect of air and root temperature, regulatedseparately, upon translocation for 6 days. For details ofapplication of C1402 see legend to figure 3. At 6 daysthe plants were harvested completely by methods describedelsewhere (13). Relative total counts X 105: control,2.2; cold air, 2.5; cold roots, 2.1. Relative total countsis equivalent to the relative specific activity times the totaldry weight in mg. Relative specific activity is the netcount per m n at infinite thickness.

Plants similar to those used in this test are shownin figure 5A and B. Because of the difference insize of the plants grown at the 2 air temperatures, itwas considered that the translocation results mightbe due to differences in vigor of the plants rather thanto the direct effect of temperature upon translocation.To settle this point, plants were grown at the normaloutdoor air temperature and transferred to experi-mental temperatures 8 days before administering theC1402 as explained in the next section.

Plants Grown at Normal Air Temperature.Plants were grown outdoors in complete nutrient solu-tion until they reached the desired size (135-145 cmtotal length of stalk). Plants of similar size wereselected and transferred to the air-conditioned climatehouses, one of which was maintained at a highertemperature range than outdoors, the other at a lowertemperature range; the control remained outdoors.After 8 days of acclimatization the translocation

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PLANT PHYSIOLOGY

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FIG. 5. Plants similar to those used in the tests inwhich the plants were grown and tested tinder the experi-

test was conducted. Air temperatures during the 90-minute period of translocation were 20, 24.5, and 33°.Translocation out of, below, and above the fed leafand joint were all positively affected by air tempera-ture (fig 6 and table I). This was a direct effect

Table I. Temiperatufre Coefficients for TranslocationPlants were grown outdoors in complete nutrient solu-

tion until they attained the desired size. Plants of similarsize were transferred to the air-conditioned climate housesfig 1), one of which was warmer than outdoors, theother colder than outdoors, with the control outdoors.The plants were allowed 8 days for acclimatization. C1409(200 Ac) was fed to a 20-cm length of blade 5 for 5 mnill-utes in sunlight at air temperatures of 20, 24, and 33°.Translocation was terminated at 90 minutes and the dis-tribution of radioactivity determined as per cent of total.

TranslocationAir

temperature Out of Down the Up thefed leaf stem* stem*

Q10 34/24 1.1 1.05 3.9Q10 30120 1.5 1.7 16.2

* Joint of fed leaf omitted from data.

upon translocation, not due to primary differences ingrowth, since the plants were approximately the samesize and had been growing at the same temperatureuntil 8 dlays before the translocation test was con-ducted.

The temperature coefficients for translocation outof the fed leaf and down the stem were less than 2,but for translocation up the stem were greater than2 (table I). The high coefficients obtained fortranslocation up the stem are in the range obtainedby Chao and Loomis (5) for stem and cell elonga-tion, suggesting that the chemical reactions involvedin upward translocation may be similar to those in-volved in cell and stem elongation, though this is notnecessarily so merely because of similar temperaturecoefficients.

The velocities of translocation were 1.40 cm perminute at 200, 1.56 at 240, and 2.00 at 330.

mental temperature conditions. A, Plants were grownas controls, at outdoor air temperature with the roottemperature regulated at 220. B, Plants were grown inthe cold house (fig 1), with the air temperature averaging80 below the outdoor temperature, when averaged for theentire growth period of the plants. Actual air tempera-tures during the experiment with C1402 are given in fig-ure 2. The root temperature was regulated at 220. C,Plants were grown at outdoor air temperature, with theroot temperature regulated at 170. Measure indicatesheight in feet. Right: full] sun (= not shaded). Left:half sun (= shaded).

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radioactivity at 90 min.method of growing the IRelative total counts X(330).

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FIG. 7. Effect of air temperature on traprofile. Value for b: 330: -7.55; 240: -7.29; CAlthough the over-all slope of the profile was n(

by the temperature of the air, the relative specties at a given distance were always positivelywith air temperature.

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The translocation profile in the stem (fig 7) hadprogressed beyond the linear stage, agreeing with ourprevious results for 90 minutes (13). The over-allslope of the translocation curve3 was not affected bythe temperature of the air, but the relative specificactivities4 at a given distance were always positivelycorrelated with air temperature.

At 90 minutes the secondary peak previously dlis-cussed (13) was still merely a deviation to the rightof a straight-line curve. The deviation appeared tobe furthest to the right at the highest air temperature.

All these results indicate that in addition to itseffects on growth and vigor of the plant, air tempera-ture has a direct effect upon translocation.

Temperature of Roots; Plants Grown and TestedUnder Experimental Conditions. At the same timethat the experiment on air temperature was conducted,the effect of root temperature was studied. Root

g temperatures of 22 (the control) and 17° were com-pared, the air temperature being the outdoor tempera-ture (fig 2) which averaged 22.4° during the test.The plants grown at a root temperature of 17° weresmaller than the control plants (root temperature of

20 220) (fig 5A and C), and translocation from the leafwas decreased (fig 3), the decrease associated withlow root temperature being considerably more severe

ribution of than the decrease associated with low air temperature.I for the At 6 days very little of the labelled photosynthate was

the C1402. retained in the roots (fig 4) due no doubt to their240), 16.1 slow rate of metabolism and growth.

Plants Grown at Normal Root Temperature. Toseparate the effect of root temperature upon growthfrom its effect upon translocation, plants were grown

nature outdoors in aerated nutrient solution with no regula-o tion of the temperature of air or roots until 3 days50 before conducting the test. Plants of similar sizeo were selected and the root temperatures were adjusted

to the experimental levels of 17 and 220. The lowerroot temperature decreased translocation both belowand above the joint of the fed leaf (fig 8). Thevelocity of translocation was decreased from 1.8 cmper minute at 220 to 1.3 cm per minute at 170. Thehigher root temperature decreased the over-all slopeof the translocation curve and increased the develop-ment of the profile, i.e., the secondary peak previouslydescribed (13) was more pronounced and further tothe right (down the stem) at 220 than at 170 (fig 9).

Plants Tested on Cloudy Days with IntermittentSun. The positive effect of root temperature ontranslocation was found on full sunny days, but noton cloudy days with intermittent sun. This may beexplained by a greater moisture stress on sunny thanon cloudy days, since translocation is known to beincreased by a high moisture content and decreased

2.3 2.4 by moisture stress (2, 9, 18), and since it is known

l0ocat8o.4 3 The value for b was calculated from the equation:,ot affected (X-i) b.ific activi- L >(-)correlated 4Relative specific activity is the net count per minute

at infinite thickness.

1.7 1.8 1.9 2.0 2.1 2.2LOG cm BELOW FED PART

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ROOT TEMPERATUREFIG. 8. Effect of root temperature on distribution of

radioactivity at 90 min. Plants were grown outdoorswith no regulation of temperature. Selected plants wereplaced at the desired root temperatures 3 days beforestarting the test. C1402 (200 gc) was fed to a centralpart of blade 8 for 5 min in sunlight and translocationcontinued for a total of 90 min. Relative total countsX 108: 1.6(22°), 1.7(170).

that low temperature decreases the absorption andmovement of water in plants (14). On cloudy days,with low transpiration, even the cold roots can ab-sorb enough water to keep the plant above moisturestress. However, on sunny days, with high transpira-tion, the cold roots cannot absorb sufficient waterbut the warm roots can, as shown by the followingdata.

The water consumption, in ml per plant per week,was as follows: for the plants at a root temperature of170, in full sun, 130 ml; in half sun, 110 ml; for theplants at a root temperature of 220, in full sun, 520ml; in half sun, 350 ml. At a root temperature of170, the water consumption of plants in full sun was

increased 18 % over that of plants in half sun; ata root temperature of 220, this increase was 49 %.On sunny days the plants at a root temperature of17° had lower moisture percentages than the plants

at a root temperature of 22°, but on cloudy days therewas little difference in moisture percentages.

Low root temperature stunted growth more in theplants grown in full sun (not shaded) than in theplants grown in half sun (shaded) (fig 5A and C).Similarly, low root temperature decreased transloca-tion when the experiment was conducted on sunnydays but not when it was conducted on cloudy days.

The Direct Effect of Temperature Upon Trans-location in Detached Blades. The results presentedso far indicate that the effects of temperature upontranslocation may be difficult to interpret because ofthe possibility that the translocation responses may besecondary to effects of temperature upon growth andmoisture content. A method of determining theimmediate effects of temperature per se, as divorcedlfrom differences due to moisture stress and growth,is by the use of detached blades (11). Translocationin detached blades was studied at 2 temperatures:50 and 22°, both at 250 ft-c. Since there was notranslocation at 50 and definite translocation at 220(fig 10), the process of translocation per se in sugar-cane definitely has a Qo greater than 1. A Qo lessthan 1 had been reported for translocation in tomatoplants by Went and Hull (17).

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FIG. 9. Effect of root temperature on translocationprofile. For growth and application of C1402, see legendto figure 8. Value for b: 220: -8.29; 170: -15.18. Theover-all slope of the profile was decreased and profile de-velopment increased by the higher root temperature.The relative specific activities at a given distance werepositively correlated with root temperature. The first 3points on the curves are the relative specific activities ofthe sheaths.

78


HARTT-TEMPERATURE AND TRAN SLOCATION IN SUGARCANE

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results for sugarcane (fig 6) indicate that the optimumtemperature for translocation of photosynthate may behigher than 30°.

0Oreo 50 Jensen and Taylor (14), working with sunflower**22° and tomato, reported that the temperature coefficient

for water movement ranged from 1.3 (through stems)0* to 1.7 (through whole plants). Since temperature

coefficients of chemical reactions are usually greaterthan 2, Jensen and Taylor concluded that physicalor physico-chemical processes are involved in watermovement in plants. A similar conclusion may bedrawn for translocation of photosynthate from theblades of sugarcane (Q10 = 1.1-1.5) and for trans-location down the stem (Q,0 = 1.05-1.7); however,the large coefficient for translocation up the stenm(Q10 = 3.9-16.2) requires a different explanation.Enzyme processes connected with metabolism in thegrowing point may be involved since it has beenshown (3) that when growth of the stem tip andyoung leaves is curtailed (due, e.g., to a deficiencyin phosphorus) translocation of C14 photosynthate to

O) 5 10 15 20 25 the growing point is decreased. Since the tempera-ture coefficients are in the same range, the chemicalHOURS reactions involved in u0 >, ard translocation may be

similar to those connected with cell and stem elonga-10. Effect of air temperature oIn translocationllntblades at 250 ft-c. Detached blades with their tion (5). Furthermore, measurements cf elongationi in tap water were preilluminated at 2000 ft-c of the stem and leaf have been used (1) to esti-~scent light) for at least 10 min. C1402 (10 Mc) mnate the rates of translocation in the tomato plant.to a 20-cm length of blade, with the lower edge of Since upward and downward translocation of C14nber placed 40 cm above the cut end, for 5 m:n photosynthate in the stem of sugarcane have differentft-c. The feeding chamber was then removed temperature coefficients, the coefficient for downwardblade was placed at a controlled air temperature, movement being that characteristic of physical or° or 220, with illumination of 250 ft-c obtained physico-chemical processes and the coefficient for up-white fluorescent tubes, for translocation periods ward movement being thach erisic fof c p-

24 hr. The blades were then subdivided and thege of radioactivity determined in the apex (above ical process, different mechanisms may be involved.part), the fed part, and the base (below the fed We know that in sugarcane both upward and down-Per cent basipetal translocation is the percentage ward translocation are the transport of sucrose in thecounts in the blade that was translocated to the phloem (13). Translocation in the blade is char-relative total counts X 106: 8.8, 8.5 (duplicate acterized by strong basipetal polarity, depends upon6 hr at 50); 8.7, 8.8 (duplicate blades, 6 hr at a positive gradient in sucrose, and require -. tight or.7, 7.1 (duplicate blades, 24 hr at 50); 8.5, 8.0 a light-formed factor (11). Although tr. locationte blades, 24 hr at 220). is primarily a push from the leaf, the amount of trans-

location is greatly increased by supplying a "sink",as in a leaf attached to a short length of stalk comn-

Discussion pared with a detached blade (11). The mechanisminvolving the pulling power exerted by growth andeffect of temperature upon translocationl has elongation of the growing point mlay be superimpose l

ed investigators for years. A good review,ubject was presented by Swan-son (16),who upon the general physico-chemical processes of trans-,ubject was presented by Swanson (16), who location. This problem is further complicated byI that the optimum temperature for transloca- the evidence (9,12) that a leafmur st compete withm bean leaves was between 20 and 30' Since

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ce, the leaves above it in translocating its sucrose into thexperiments reveal a similar optimum curve, stem. Further discussion of how temperature affectsIn concluded that translocation is influenced byiture in much the same way as are most other translocation will be deferred until after the presenta-)gical processes although evidence, largely in- tion of the results of studies on the effect of lightcontrary to this generalization has been pre- upon translocation in sugarcane, which suggest aby Went and Hull (17). Nelson (15) stated photocontrol theory of translocation (9).nperature has different effects upon the sep- Studies of the effect of temperature upon trans-mponent parts of translocation, and mentioned location in sugarcane have a 3-fold purpose. First,shed data of Mortimer which indicate that they may aid in obtaining a hint as to the mechanismicrose has entered the vein, its translocation involved. Progress in this direction was obtainedithe petiole is unaffected by temperature. The by the study of temperature coefficients indicating the

79


PLANT PHYSIOLOGY

involvement of both physical and chemical processes.

Second, they may aid in securing a basis of under-standing other results. For example, Davis andSingle (6) stated that should cool root temperatureactually retard movement in the phloem, resulting incongestion of substances in the shoot which can de-press metabolic activity, a basis may be provided forunderstanding some effects of cool root temperatureson shoot growth and mineral accumulation in thetomato. Definite evidence is now presented that lowroot temperatures on sunny days do actually retardtranslocation from the leaf, although the leaf is ata normal air temperature. Such retardation leadsto the accumulation of sucrose in the blade, whichmay in turn depress the rate of photosynthesis (8)and thus decrease yield. Furthermore, p32 fed to theroots of similar plants, accumulated in the leaves.This accumulation indicates that cooling the roots per-

mitted some upward movement of inorganic p32 in thexylem, but slowed the return translocation of organiccompounds of p32 in the phloem as it does the photo-synthate (4). Third, tests on translocation in de-tached blades of selected commercial varieties at con-

trolled air temperatures may lead to a method ofselecting varieties best suited for growing at varioustemperature ranges.

Fujiwara and Suzuki (7) have also stressed theimportance of both top and root temperature. Theyreported that the rate of translocation in barleyreached its maximum when the tops of the plantswere maintained at the optimum temperature forphotosynthesis and the roots maintained at the opti-mum temperature for respiration.

Low temperature of either air or roots may de-crease the transport of sucrose in sugarcane plants.The effect of air temperature is direct; the effect ofroot temperature is indirect, probably due to its pri-mary effect upon absorption of water.

Several important references have come to theattention of the author since this paper was written.Sekioka studied the effects of soil and air tempera-ture upon respiration and translocation in sweetpotato plants. The respiratory loss of carbohydratein the leaves increased with temperature from 10 to40°. Translocation from the leaves was optimumat 300 but accumulation in the roots was optimumat 200 due to the differences in respiration. Whenthe effect of air temperature upon respiration in theleaves was prevented by holding the air temperatureat 250 and varying only the root temperature, theaccumulation of foliar-applied sucrose-C'4 or p32 inthe roots was best at a root temperature of 300.(Sekioka, H. 1963). The effect of some environmentalfactors on the translocation and storage of carbohy-drate in the sweet potato, potato and sugar beet.I. Relationships 'between the translocation of carbo-hydrate or radioisotopes and the soil and air tempera-tures. Sci. Bull. Fac. Agr. Kyushu Univ. 20: 107-18(Japanese with English summary); II. Relation-ships between the translocation of carbohydrate or

radioisotopes and temperature gradient in the sweet

potato. Sci. Bull. Fac. Agr. Kyushu Univ. 20:119-30 (Japanese with English summary).

In a paper on translocation in Pteridium, Whittlereported that at higher temperatures profiles changemore rapidly in form from the wave to the transitionto the diffusion form. In a paper on translocationand temperature, Whittle reported that the apparent( iffusion constant for translocation in Pteridiurn,derived from profiles obtained at temperatures from13 to 290, was temperature-dependent with a Q1o =2.9. This result supports a translocation mechanismof the activated-diffusion type, according to Whittle.(Whittle, C. M. 1964). Translocation in Pteridium.Ann. Botany (London) 28: 331-38; Translocationand temperature. Ann. Botany (London) 28: 339-44.

SummaryExperiments dealing with the effects of air and

root temperature, regulated separately, upon trans-location of C14 photosynthate in sugarcane are de-scribed,

The temperature of the air directly affects thepercentage of C14 photosynthate translocated from thefed blade, as well as the percentage moved up anddown the stem. It also affects the velocity of trans-location down the stem. These results are inde-pendent of any direct effect of air temperature upongrowth.

The temperature coefficient was 1.1 to 1.5 fortranslocation from the fed blade, 1.05 to 1.7 fortranslocation down the stem, but 3.9 to 16.2 fortranslocation up the stem, which indicates that trans-location from the leaf and down the stem involvesphysical or physico-chemical processes, whereas trans-location up the stem is controlled by chemical pro-cesses, e.g., the metabolism of cell growth.

Cold roots decreased translocation from the leafonly at high light intensities when the plants at lowroot temperatures were under greater moisture stressthan the plants at normal root temperature.

In detached blades tested at 250 ft-c, there was notranslocation at 50 and definite translocation at 220.

AcknowledgmentsThe author is grateful to Miss Ada Forbes and Mrs.

Grace Sadaoka for technical assistance, and to HughBrodie for some of the plants, for the use of the climatehouses, and for the data on the consumption of water.

Literature Cited1. BOHNING, R. H., W. A. KENDALL, AND A. J. LINCK.

1953. Effect of temperature and sucrose on growthand translocation in tomato. Am. J. Botany 40:150-53.

2. BURR, G. 0. 1962. The use of radioisotopes bythe Hawaiian Sugar Plantations. Intern. J. Appl.Radiation Isotopes 13: 365-74.

3. BURR, G. O., C. E. HARTT, H. W. BRODIE, T. TANI-MOTO, H. P. KORTSCHAK, D. TAKAHASHI, F. M.ASHTON, AND R. E. COLEMAN. 1957. The sugar-cane plant. Ann. Rev. Plant Physiol. 8: 275-308.

Ao



4. BURR, G. O., C. E. HARTr, T. TANIMOTO, D. TAKA-HASHI, AND H. W. BRODIE. 1957. The circula-tory system of the sugarcane plant. Radioisotopesin Scientific Research: Proc. 1st (UNESCO) In-tern. Conf. 4: 351-68. Pergamon Press, NewYork.

5. CHAO, M. D. AND W. E. LooMis. 194748. Tem-perature coefficients of cell enlargement. Botan.Gaz. 109: 225-31.

6. DAVIS, R. M. AND J. C. SINGLE. 1961. Basis ofshoot response to root temperature in tomato.Plant Physiol. 36: 153-62.

7. FUJIWARA, A. AND M. SUZUKI. 1961. Effects oftemperature and light on the translocation of photo-synthetic products. Tohoku J. Agr. Res. 12:363-67.

8. HARTT, C. E. 1963. Translocation as a factor inphotosynthesis. Die Naturwissenschaften 50:666-67.

9. HARTr, C. E. 1964. Translocation of sugar in thecane plant. 1963. Reports, Hawaiian Sugar Tech-nologists, 22nd Annual Conference, November18-21, 1963: 151-67.

10. HAR-r, C. E. AND H. P. KORTSCHAK. 1963. Trac-ing sugar in the cane plant. Proc. Intern. Soc.Sugar Cane Technologists, 11th Congr. 1962:323-34.

11. HARTT, C. E. AND H. P. KORTSCHAK. 1964. Sugargradients and translocation of sucrose in detachedblades of sugarcane. Plant Physiol. 39: 460-74.

12. HARTT, C. E., H. P. KORTSCHAKFtAND G. 0. BURR.1964. Effects of defoliation, deradication, anddarkening the blade upon translocation of C14 insugarcane. Plant Physiol. 39: 15-22.

13. HARrr, C. E., H. P. KORTSCHAK, A. J. FORBES, ANDG. 0. BURR. 1963. Translocation of C14 in sugar-cane. Plant Physiol. 38: 305-18.

14. JENSEN, R. D. AND S. A. TAYLOR. 1961. Effects oftemperature on water transport through plants.Plant Physiol. 36: 63942.

15. NELSON, C. D. 1963. Effect of climate on the dis-tribution and translocation of assimilates. In: En-vironmental Control of Plant Growth. L. T.Evans, ed. Academic Press, New York. p 449.

16. SWANSON, C. A. 1959. Translocation of organicsolutes. In: Plant Physiology, A Treatise. F. C.Steward, ed. 2: 481-551.

17. WENT, F. W. AND H. M. HULL. 1949. The effectsof temperature upon translocation in the tomatoplant. Plant Physiol. 24: 505-26.

18. WIEBE, H. H. AND S. E. WIHRHEIM. 1962. Theinfluence of internal moisture deficit on transloca-tion. Plant Physiol. suppl. 37: L-LI.

Natural Variations in the Physiological Characteristicsof Growing Chlorella Cultures 1" 2

Peter M. Shugarman and David ApplemanDepartment of Botany and Plant Biochemistry, University of California, Los Angeles

In an investigation of the effects of 3-amino-1,2,4-triazole on the synthesis of chlorophyll in ChloreUacells it was discovered that not only does the additionof this compound at certain concentrations causeimmediate and complete cessation in the synthesis ofchlorophyll but also that the untreated cells producechlorophyll at a nonuniform rate. The latter obser-vation caused us concern in the interpretation of theresults of the treatment and led to this investigationinto the normal variations in the production of chloro-phyll and in photosynthetic 02 evolution in growingChlorella cultures.

Materials and Methods

The organism used is Chlorella vulgaris Treleasestrain obtained from Granick, which grows rapidlyon an inorganic medium consisting of 30 mm KNO3,10 mM MgSO4, 1 mm Ca(NO,)2, 4 mm KH2PO4,0.85 mm FeSO4 (as EDTA chelate) and micronu-

'Received July 7, 1964.2 Research supported by NSF Grant No. G-18479.

trients (1) 1.5 ml per liter of medium modified tocontain in addition 10 mm NaCl and 13 mm NH4VO,.

The cultures are grown in tubulated 500 ml Erlen-meyer flasks with continuous shaking. Aeration iswith a mixture of 5 % CO. in air. Illumination isfrom below and is continuous at an incident 750 ft-cusing incandescent bulbs. The temperature is main-tained at 26 to 280.

Increase in cell mass is determined by centrifugingan aliquot of suspension in Hopkins vaccine tubes,Fitch modification, and determining the amount ofpacked cells per ml of suspension.

Chlorophyll is determined following extractionwith absolute methanol by the method of Mackinneyusing a Cary 14 spectrophotometer (6). Methanolwas chosen because of the extreme ease with whichit extracts the visible pigments of this species. Com-parison with the other currently used chlorophyllassay methods [Arnon (2), Warbusrg~-4&), Gaffron-(3)] showed this method to yield comparable results.

Photosynthetic 02 evolution was determined usinga Clark-type polarographic electrode in a thermo-

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