In a series of experiments using sugar beets, researchers investigated the effects of varying cycles lengths on growth (0.37 hr to 48 hr). Each cycle was equally divided into a light and dark period so that each treatment regardless of cycle length received the same amount of light over the 17 weeks of the experiment. Two growth parameters were used to evaluate the effects of cycle length, total fresh weight and sucrose content of the storage root. Both parameters showed very similar responses in that under long cycles (12 hr or greater) growth was normal, whereas plants growing under shorter cycle periods were progressively inhibited. Minimum growth occurred at a cycle period of 0.75 hr. The yield at the 0.75 hr cycle, where was at a minimum, for total fresh weight was only 51 percent compared to the 24 hr cycle. The yield of sucrose was even more reduced at 41 percent of the 24 hr cycle

Berry, W.

Hoshizaki, T.

Ulrich, A.

English

NASA Technical Reports Server

THE EFFECT OF ULTHADIAN AND Okbil'AL 
CYCLES ON PLANT GROWTH 
Wade 0errgl.Takashi ~oshizaki2 
Albert ~lrich3 
1. Lab. of Biomedical Environmental Sciences, UCLH 
2. Jet Propulsion Laboratory, CI'T,  Pasadena 
3. Department of Plant and Soil Biology. UCB 
ABSTRACT 
All llfe on earth has developed under the 24 hr light dark 
cycle dictated by the earth's daily rotation. There is little 
information on the degree to which plant qrowth is obliqated 
to this 24 hr cycle nor the effect of short cycle length on 
, . .  
growth. In a series of experiments using suqar beets, we 
investigated the effects of varying cycles lengths on qrowth 
(0.37 hr to 48 hr). Each cycle was equally dlvided lnto a 
light and dark period so that each treatment regardiess of 
cycle length received the same amount of light over t h e  17 
weeks of the experiment. We used two growth parameters to 
evaluate the effects of cycle length, total fresh weiuht and 
sucrose content of the storaqe root. Both parameters showed 
very similar responses in that under long cycles (12 nr or 
greater) growth was "normal", whereas plants growing under 
shorter cycle periods were proqressively inhibited. Mlnimum 
growth occurred at a cycle period of 0.75 hr. The yield at the 
0.75 hr cycle, where was at a minimum, for total fresh weluht 
wae only 51 percent compered to the 24 hr cycle. 'fne yield of 
sucrose waa even more reduced at 41 percent of the 24 hr 
cycle. 
https://ntrs.nasa.gov/search.jsp?R=19860010469 2020-03-20T15:10:08+00:00Z
INTRODUCTION 
In recent years . much effort has been nut $orth t o  iearn 
how t o  grow plants in a controlled ecological life support 
system (CELSS) type environment (Wheeler and Tibbitts, 19841. 
These efforts are reflected in the Total a iarge number of 
NASA-sponsored workehops and symposia (Tibbitts end Alfora, 
1980: Moore et a1.,1982; Fabricant, 1983) that have been and 
are planned t o  be held, and in the lncreasinq number of papers 
published on thls subject. Generally, the research has been 
directed toward the selection of candidate species, cultural 
methods and strategies t o  maximize food production In the 
minimum of time and space. Attention is now turninq t o  
concepts of how-to maximize production per unit of enerqy 
used.Thue lighting becomes of concern due to ~ t s  high energy 
demands. The energy requirement of liqht for photosynthesis 
can be managed through the manipulation of intenaity, duration 
and integration time wise with other enerqy requirinq 
functions. 
The proposed space station in low earth orbit will be in 
sunlight for approx~mately one hour and darkness 30 min. of 
each orbit, i.e. and orbital photoperiod. Thus the available 
power from solar panels or direct sunlight will cycle on and 
off every 90 mln. This means that any horticultural system 
growing plants on a 24 hr cycle will require engineerinq 
support. The question which arises from this is whether from a 
horticultural point of view there are significant benefits 
from growing on a 24 hr cycle or is it posalble to achleve 
adequate plant production independent of cycle lenqth. because 
of the orbital photoperiod which the proposed space station 
will occupy it is desirable to known if suqar beet, a plant 
i 
selected for CELSS (Tibbitts and Alford 1980) is affected by 
. - 3  
cycle length. 
. . * I .  
METHODS A N D  MATERIALS 
Ten seedballs of sugarbeet (Beta vulgaris L.), equally 
apaced, were placed in 8 circle 12 cm In diameter, and planted 
to a depth of 2.0 cm in No. 2 vermiculite contained In 
1 1  I .  
20-liter pots lined with 1.5-ml polyethylene liners. The 
seedlings as they grew were gradually thinned to two plants 
. - 
. , * * , -  
per pot. The plants were watered daily with one-half strength 
Hoeglands nutrient solution (Hoagland and Arnon 1950) modified 
to include 0.5 m M  NaCl (Ulrich et al. 1958). Plants from the 
time of planting to harvest were grown in controlled 
I 
environment chambers (127 X 249 X 137 cm.). The temperature 
was a constant 20 degrees C and illumination was 650 
uE/cm2/sec of photoeyntheticolly active radiation supplied 
80% by cool-white VHO fluorescent lamps and 20% by 
incandescent 1amps.The relative humidity was not controlled 
but was approximately 70% ambient C02 was used wlth about 
20% make up air. A sinqle growth chamber was used for each 
treatment. At the start of the experiment each chamber 
contained thirty-two LO-liter pots placed in a 4-row b y  8- 
column pattern. Each harvest consisted of eight plants with 
t w o  plants taken from each column. At the flnal harvest eacn 
chamber had a single row of eight pots along the center of the 
chamber. Plants were harvested at 5, 9, 13 and 17 weeks after 
planting. Fresh weights of tops and storage roots were taken 
on a pot basis and dried in a 70 degree oven for dry weiqhts. 
Samples of pulp from the etorage root were analyzed for 
sucrose. 
RESULTS AND DISCUSSION 
Figure 1 shows total yield fresh weight as a function o* 
cycle length ( cycle length in this paper is expressed as the 
sum (hr) of a consecutive light and dark period). 
FIGURE 1 The total fresh weight per pot including the 
storage root (average of 8 pots/2 plants each in grams). <1P = 
9 weeks; + = 13 weeks; X = 17 weeks) 
The three curves show the total fresh weight for harvests 
at 9, 13 and 17 weeks ae a function of cycle t~me. The curve 
depicting the 9 week harvest for total fresh weight clearly 
shows that at a cycle time of 0.75 hr there occurs a minimum 
in yield. Yield increasee at both longer end shorter cyclee 
times. However the largest yields are always associsted wlth 
the longer cycle times. The 17 week yield curve also shows a 
minimum at 0.75 hr cycle time. However in this curve the 
difference in yield between the longer and shorter cycle times 
is much more pronounced. This seems to indicate that as the 
plant agea, that the longer cycle tlmes become more important 
in relation to yield. The importance of the yield minimum at 
0.75 hr may only be in its relationship to the mechanism of 
action of this cycle phenomena. The response of the 13 week 
harvest as would be expected is somewhat intermediate between 
the other two harvests. 
The curves in figure lare a composite of two ex~erlments 
run at different times in a single set of qrowth chambers one 
experiment covered cycle txmes from 0.87 to 1.5 hr and the 
other from 1.5 to 48 hr.. Although the environmental 
parameters and cultural prscticee were designed to be 
identical for both experiments. The experiment with the longer 
cycle treatments did show differences in yield in the 
overlapping treatment at 1.5 hr cycle time. Thls is most 
clearly shown in the 17 week harvest by an offset in the sraph 
at the 1.5 hr cycle time where the two experiments have an 
569 
overlapping treatment( figure 2). 
C.'f !:I-E LEf  !'3 T+! H F  
FIGURE 2 Total fresh weight without normalization of the 
data from the experiments with the longer cycle length~~l.5 to 
48 hr. 
( B P  = 9 weeks; + = 13 weeks: X = 17 weeks) 
This difference between experiments, run at different 
times but in the same set of growth chambers, in the 
nonnormalized curves does provide additional evidence that 
common cultural practices, although they do affect yield, do 
not seem to affect the observed responses related to cycle 
time. 
The yield differences shown in figure 1 are not small in 
that even a conservative estimate indicates a yield of 50 to 
30 percent for weeks 9 and 17. Thus if the growth differences 
are calculated for the 9 week harvests for the lonqer cycles 
(12 to 48 hr) and compared with the 0.75 hr cycle plants (45 
min) there rs a difference of 66 percent. Wnen calculated for 
the 17 week harvest the yield difference 1s decreased but 18 
still 50 percent. Slmilar cycle treatments to buckwheat and 
cosmos by Garner and Allard (1931) showed an even greater 
yield difference, in some cases as much as 88 fold difference. 
The yield curves for the three different harvest dates all 
show the same general shape curve in that there is a minimum 
at the 0.75 hr cycle time with higher yields at both shorter 
an longer cycle times. However the size of the mlnimum at 0.75 
hr is leas at the later harvests. The high degree of 
parallelism between the curves for these three harvests is 
strong evidence that this phenomena is related to the variable 
of this experiment, cycle time rather tnan some specific 
aspect of a certain phase of growth and development. These 
sugar beets at the time of the 17 week harvest were larqe 
plants, thus these plants have passed through all the urowth 
stages up to flowering. 
Sugar beets are rather unique in that, in adaitlon to 
total biomass being a good index of yield, the percent sucrose 
in the storage root is an excellent index of the amount of 
photoeynthate available to the plant in excess of its needs 
for immediate growth. Thus if the concentration 02 sucrose is 
graphed as a function of cycle time it ehou1.d provide a 
independent evaluation of the effects of cycle time on 
photosynthesis versus other aspects of plant growth and 
development. Figure 3 shows this graph where there is also a 
minimum in eucrose concentration at the 0.75 hr cycle tlme 
which continues up to the 13 week harvest. 
ORIGWAE PAGE i% 
.OF POOR QUBLlTY 
FIGURE 3 Sucrose vercentage In the storase root. Each 
harvest curve is the average of 8 pots/ 2 plants eacn. (9 = 9 
weeks: + = 13 weeks; X = 17 weeks) 
Thls minimum in sucrose concentratlon occurs in 
conjunction with a minimum in blomaes. If the photosynthetic 
capacity of the plant had remalned the same. t h e n  rn the 
presence of reduced qrowth as occurrea unaer t.he 0.75 hr cycie 
it would be expectea that the sucrose concentration woula nave 
risen. However as eeen in figure 3 there is aiso a minlmum In 
sucrose concentration. This reduction in sucrose concentraclon 
has to be related to a qreater effect of the cycle treatment 
on the photosynthetic mechanism than the rest of the plants 
growth and development. 
However at the 17 week harvest there does not appear to be 
a minimum but rather a constant decline in sucrose 
concentration with decreasing cycle time. This seems to imply 
that at the 0.75 hr cycle time there 1s a minimum in tne 
amount of photosynthate available for srowth. All ~ l a n t s  ln 
these experiments received the same amount of total Ilqht the 
only difference being cycle lenqth. Thus the observed 
difference can not be related to differences in tne amount of 
light received but only to dxfferences in the piants ablllty 
to utilize this liqht. The work of Bonde (1955) showea a 
minimum in chlorophyll content in the leaves of cocklebur 
under cycle times less than an nour. He also ~naicaced that 
the chloraphyll decrease was equally noticeable at three liaht 
intensities 500. 1000. and 1500 FC. However he reached the 
conclusion that yield reductlon was not due to etfects on the 
photosynthetic mechanism because sucrose sprays had no 
offsetting effects on yield reductlon cBonde 1956). 
Unfortunately he dld not determine if in fact the sucrose was 
absorbed by the plant. The change in the characteristlcs oi 
the curve at the 17 week harvest in (flqure 3 )  to lust a yield 
decrease at shorter cycles times rather than the ciear uisplay 
of a minimum at 0.75 hr seems to suggest that there ls a 
degree of adaptation with ase to at least one aspect of the 
reduction in photosynthate. Tne consrstent decrease oz sucrose 
percentaqe with decreasing cycle lenqth compared with the 
break in slope (at the 12 nr cycle length oi m e  total fresh 
welght in the 17 week harvest (figure 1) would suqqest that 
with increasing aqe longer cycle lengths may be more 
favorable. 
FIGURE 4 Total sucrose per pot. Each harvest curve 1s the 
average of 8 pots/ 2 plants each. <4B = Y weeKs: + = 13 weeKs;  
X = 17 weeks) 
The amount of sucrose accumulated in the root as a 
functlon of cycle lenqth and harvest date is shown In flqure 
4. Thls aspect of y ~ e l d  also shows the same qeneral trend In 
that increased yield is definitely associated wlth lonqer 
cycle lengths, 12 hr or longer. The hlgher yiela at the 
shorter cycles compared to the 0.75 hr cycle could be a very 
important factor in determlnxng the mechanism of action but 
there is still a 30 percent decrease in comparison to the 
longer cycles. This seems to indicate that the longer cycle 
times will be necessary for the nlqher growth rates. These 
observed responses to cycle lenqth is not predictable from 
standard text book plant pnysioloqlcal principles.The 
experiments reported here show that the plants response to 
differences in the llqht dark cycle lenqth even thouqh the 
total light recieved during the duratlon of the experiment was 
identical. 
L I I ' ~ R A ? ' U H E  CITED 
Bonde. E. K. 1955. The effect of various cycies of i ~ s h t  
and darkness on the qrowth of tomato and cocklebur plants. 
Physiol. Plantarium 8.:913-923. 
Bonde, E. K. 1956. Further studies on the effect o* 
various cycles of ~ l g h t  and darkness on t h e  growth of tomato 
and cocklebur plants. Physiol. Plantarlum 9:51-54. 
Fabricant, J. D. 1983. The Fabrlcant report on life 
sciences experiments for a space statlon, Unlv. of Texas 
Medical Branch. Galveston. T x .  77550. 
Hoagland, D. H., and D. I. Arnon. 1950 The water culture 
method for growing plhnts without soil. p. 32. Callf. Aqr. 
Exp. Sta. Cir. 347. 
Garner, W. W., and H. A. Allnrd 1931. Eifect of nbnormaliy* 
long and short alternations of light and darxness on qrowtn 
and development of plants. J. Agr. Hes. 42:629 
Moore, B., 111, R. A. Wharton, Jr., and R. D. Mac Elory. 
1982. Controlled ecological life support system. Proc. of N H ~ H  
meeting held at the Univ of Mew Hampshire, Durham, NU., May 
3-6, 1981. NASA Conf. Pub.'2247, NASA Sci ana Tech. In2o. 
Branch. 
Ohki, K. and A. Ulrich-1973. Suqarbeet growth and 
development under controlled climatic conditlons with 
reference to night temperature. J. Hmsr. Soc. Suaar beet 
Technol. 17:270-279. 
Tibbitts, T. W. and D. K. Alford. 19b0 Use 0% hlaher 
plants in regenerative life support systems. NSG - 2405, NA S A  
Ames Research Center. Hoffett Field, Ca. 94035. 
Wheeler, R. M. and T. W. Tibbitts. 1984. Controlied 
ecological llfe support system, hlgher plant fllght 
experiments. NASA contractor report 17'7323. NASA Ames tiesearch 
Center, Moffett Field, Ca.'94035. 
ULrich, A. et al. 1958. Effects of cllmate on suqar Deeto 
grown under standardized conditlons. J. ~ m e r .  Soc.  Suqar Beet . 
Technol. 10:l-23. 


The effect of ultradian and orbital cycles on plant growth

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