The establishment, maintenance and use of the NASA-UCSC Botanical Centrifuge is discussed. The broad goals of this project were: (1) to establish facilities for conducting experiments under conditions of sustained centrifugation; (2) to pursue research on the gravitational physiology of higher plants; (3) to develop experimental hardware suitable for studies of plant development in the weightless condition; and (4) to accommodate visiting investigators whose researches are of interest to the NASA Biomedical Program and who may require for some limited time, the use of a medium size centrifuge with associated facilities appropriate for plant physiological studies

Brown, A. H.

English

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FINAL TECHNICAL REPORT
Research on the Effects of Altered Gravity and
Other Factors on the Growth and Development of
Higher Plants
Contract No. NASW-2208
Report Prepared by: A.H. Brown
Date: 21 November 1973
CONTENTS
I. Introduction . . . . . . . .................. .. . . Page 3
II. Progress on Individual Research and
Development Tasks . . . . . . . ... Page 4
A. Establishment of research facilities
B. Experiments on gravitational
physiology of higher plants
C. Development of experimental hardware
for space flight missions
III. Special Problems of Instrumentation or
Equipment Maintenance . ............ Page 6
A. Centrifuge oil leaks
B. Air conditioning
C. Gas communication to centrifuge payloads
D. Centrifuge vibration mounts
E. Centrifuge protective circuitry
F. Recording photographic images
G. Clinostat drive motors
H. Maintenance provisions
IV. Directions of Future Research
and Development . . . . . . . . . ..... Page 9
A. List of scientific tasks
B. Accomodation of visiting investigators
V. Reports and Memoranda . ..... . .. .............. Page 11
VI. Personnel . .................... Page 12
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I. INTRODUCTION
The broad goals of this project have been: (a) to establish
facilities for conducting experiments under conditions of sustained
centrifugation, (b) to pursue research on the gravitational physiology
of higher plants, (c) to develop experimental hardware suitable for
studies of plant development in the weightless condition, and (d)
to accomodate visiting investigators whose researches are of interest
to the NASA Biomedical Program and who may require for some limited
time, the use of a medium size centrifuge with associated facilities
appropriate for plant physiological studies.
Since the termination of the present contract our project has
received support from NASA grant, NGR 39-030-010. In that way the
continuity of our efforts was ensured. As this is a continuing project
it does not seem appropriate that we should attempt to sum up all
our results in final form at this time. Accordingly this "Final Report"
is more in the character of a progress report and as such it will
emphasize progress we have made especially since our last Technical
Status Report (1) of December 1972.
Our studies also have been supported by a contract between NASA
and the University of Pennsylvania (NAS 2-2432). Research under that
contract was designed to complement our efforts under the U.C.S.C.
contract. The provision of two separate contracts has been justified
chiefly as an administrative convenience. Some specific research
tasks have been supported in part by both contracts. However, for
reporting purposes we shall emphasize here those tasks which relate
most directly to the establishment, maintenance, and use of the NASA-
UCSC Botanical Centrifuge.
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II. PROGRESS ON INDIVIDUAL RESEARCH
AND DEVELOPMENT TASKS
A. Establishment of Research Facilities. The Botanical Centrifuge
was installed early in 1972. However, to bring the machine to a
condition of research readiness required many months. Considerable
instrumentation was necessary and serious unforseen problems were
encountered with the air conditioning system and with the operation
of the centrifuge itself. Some of these difficulties were noted in
an earlier report (1). The several problems were either solved or
at least were under control and the accessory apparatus was at hand
so that biological experimentation on the Centrifuge could begin
on 17 May 1973.
B. Experiments on Gravitational Physiology of Higher Plants.
Three tests of sustained acceleration effects were carried out prior
to the termination of the subject contract. Two were designed mainly
to observe the effects of chronic acceleration on the development
of Arabidopsis seedlings over a range of g-levels. Both tests were
3 weeks in length. One test was initiated chiefly to examine nutational
movements of sunflower hypocotyls at different g-levels. A major
objective in all three tests was to evaluate equipment and procedures
and to identify operational shortcomings so these could be rectified.
In addition there were six different scientific tasks represented among
the experiments in the three tests. (See section IV. A. for task
descriptions).
The following table shows the scientific yield obtained from the
biological experiments. Values less than 100% indicate partial test
failures.
Expt. No. g levels Duration Scientific Percent
employed of test Tasks Data Yield
Involved
BCT - 1 1,5,10 21 days GXTRAP 100%
CNTCLN 50%
CYTHST 50%
NULTST 0
BCT - 2 1,8,15 21 days GXTRAP 100%
REVPOL 100%
NUTFOG 0
CYTHST 100%
BCT - 3 1,10 3 days NUTFOG 100%
SCIRCAD 100%
Further information on the first two tests will be found in two
memoranda (4,5); a similar concise summary of the third test is in
preparation (6).
-5-
In these tests (and in those which have been performed since the
termination of the subject contract) two or three different experimental
payloads have been centrifuged simultaneously. It has not been difficult
to schedule multiple purpose tests on the Centrifuge because of the
relatively large payload capacity which is available and because the
design of experiments and evaluation of results usually takes much
less time than does the centrifugation exposure.
C. Development of Experimental Hardware for Space Flight Missions.
An important but not urgent task before us is the further evaluation
of the performance of the Advanced Development Hardware for the
Arabidopsis flight experiment (coded ADHGSE). Only one biocompatibility
and performance test was conducted soon after the hardware was delivered
by the subcontractor (7). Lack of funds and technical assistance
prevented a continuation of the testing program at that time. Making
the Centrifuge research ready has consumed all the time of the available
technically competent personnel who otherwise could have resumed work
on ADHGSE.
-6-
III. SPECIAL PROBLEMS OF INSTRUrENTATION
AND EQUIPMENT MAINTENANCE
A. Centrifuge Oil Leak. The Centrifuge main bearing is lubricated
with oil of rather low viscosity. Originally the sealing gasket on
the drive shaft was not tight enough to prevent unacceptable oil leakage.
The subcontractor who fabricated and installed the Centrifuge attempted
to correct the fault by several kinds of face seals because access to
the faulty seal was extremely difficult. These attempts were unsuccess-
ful and finally the machine was partly disassembled so that the shaft
seal could be replaced. Thus the problem was corrected.
B. Air Conditioning. The system design calls for the compressor
to operate continuously. Heat inputs to the system are chiefly the
Centrifuge itself and a duct heater which is thermostatically controlled.
The duct heater was found not to be large enough (with the Centrifuge
running at low speed) to balance the cooling capacity of the refriger-
ation unit. The system has been improved by two expedients. Supplementary
electric heaters (manually adjusted) can add more heat to the Centrifuge
rotunda. Also a hot gas bypass line was installed in the refrigeration
unit and this has the capability of reducing the effectiveness of
cooling. The bypass is controlled by a valve whose opening can be
adjusted manually. Thus, by forsaking fully automatic operation,
we have been able to achieve the desired control of temperature in
the Centrifuge rotunda over the full range of Centrifuge operating speeds.
C. Gas Communication to Payloads. The Centrifuge design included
a rotary gas joint which can be used to communicate gas pressure to
experiments in the payload cradles. So far our experiments have not
required this facility. The gas pipe runs from the rotating joint
element through the axis of centrifuge rotation inside the slip ring
assembly. It was weakened by the threads which had been cut into the
pipe in order to attach a fitting. The pipe broke at the threaded
end during centrifugation. However, it was removed before the slip
rings were damaged. This facility is not needed urgently but at some
future time it will have to be replaced.
D.- Vibration Mounting. The Centrifuge was anchored to the concrete
floor at the time of installation. Communication of vibration across
the Centrifuge base-floor interface proved to be excessive and un-
desirable. Improved vibration mounts were obtained and these were
inserted between the Centrifuge base and the floor. The transmission
of vibration was reduced substantially.
E. Centrifuge Protective Circuitry. Three kinds of warning or
automatic protective devices are in use.
1. Bearing temperature protection device - A commercially
available temperature indicator and safety power cutoff circuit was
modified so that it can function as a protective circuit as well as
display the Centrifuge bearing temperature. The sensor was mounted
on the Centrifuge main bearing housing and the limiting temperature
-7-
is selected by the operator. In case of bearing overheating (as
might results from loss of lubricant or mass asymetry) the Centrifuge
will be shut down automatically and only manually can it be restarted.
This protection device works as desired. It is required in order
that the Centrifuge may be operated unattended for periods of time.
2. Vibration sensor and protective device - A commercially
available vibration sensor with accompanying circuitry was installed
on the base of the Centrifuge. The system responds to very low
frequency vibrations. In the event of serious imbalance the oscillation
(at the frequence of Centrifuge arm rotation) will be sensed and the
Centrifuge will be shut down automatically. The sensitivity of this
safety device is adjustable. The Centrifuge may be operated safely even
when it is out of balance by several hundred g x lb but to reduce wear
we keep the payloads balanced within 2 or 3 lb (static) or within about
50 g x lb at full speed. The protective device works as intended.
3. Power interruption - Occasional power outages occur.
Usually these are very brief. The causes vary. We must accept the
non-trivial probability that in any given experiment power to the
laboratory may be interrupted. The Centrifuge is designed so that,
should power go off, it will restart as soon as the power is restored.
Some of the experimental equipment may malfunction if power is turned
off even briefly. It is important that we should be made aware of
such an event especially if it occurs when the Centrifuge is running
unattended. At present, a warning siren (battery operated) is sounded
whenever power is interrupted. It must be reset manually after power
is restored. If the event occurs when the centrifuge is unattended,
an indicator light establishes that fact even though the power has come
on again. The duration of the power interruption can be determined from
the time discrepancy shown by an electric clock.
F. Image Recording. We have not attempted to photograph events
on film in cameras on board the Centrifuge although we do have this
capability. Instead we have employed TV cameras and we inspect
the images in real time or more frequently these images are recorded
on audio tape. Instead of duplicating camera plus recording system
for each of several experimental subjects under observation at the
same time, we have recorded a sequence of up to three different
camera images on the same tape. Our interests are almost exclusively
related to time lapse records so every 10 min or 15 min or other
chosen interval a programmed sequence of images is recorded. These
images usually are transferred to film by using a camera to photograph
the video monitor screen. By use of a tone discriminating circuit
only one particular TV cameras image can be photographed in sequence
since it was identified on the video tape by an audio tone at the
moment of taping. For our purposes this system has been functioning
satisfactorily.
G. Clinostat Drive Motors. We have constructed enclosures for
certain kinds of biological test subjects (including Arabidopsis seedlings)
which are essentially cubic boxes. Each such box is equipped with
lights, a ventilating fan, a bank of clinostats geared to the same
drive motor, a thermistor, and a photocell. The cubic shape permits
the box to be installed in a Centrifuge payload cradle in any desired
--
orientation. Four such Boxes were constructed locally to fit the
four Centrifuge cradles. They are used routinely for experiments
with Arabidopsis. In the course of experiments at the higher end
of our attainable g-range we discovered that the clinostat drive motors
in the Cubic Boxes would stall under g-loading. That problem was
traced to the performance of the motor itself - not the clinostat
array which is coupled to it. Until the problem is solved we cannot
operate clinostats reliably above about 5 to 8 g. At the time of
termination of the subject contract the problem had not been overcome.
H. Maintenance Provisions. Funding limitations on this project
are severe. We have not found it possible to include a budget item
for maintenance. Like all machines we can expect that the Centrifuge
will require some repairs in the course of time. The ancillary equip-
ment which is equally important for the successful conduct of research
with the Centrifuge also cannot be expected to require zero maintenance.
We have not purchased a maintenance contract from the manufacturer of
the Centrifuge nor from the subcontractor who installed the air
conditioning system. Both the Centrifuge and the air conditioning
system components are beyond their warranty periods. We have been
fortunate that repairs to equipment have not become a serious
financial burden during the life of this contract. The problem of how
to avoid future interruptions to our experimental program because
we have failed to provide for contingencies has not been solved and
has carried over into the current period of grant support.
-9-
IV. DIRECTIONS OF FUTURE RESEARCH
AND DEVELOPMENT,
A. Scientific Tasks. There are 12 uncompleted tasks we now
can identify as being relevant to our project which require the use
of the Centrifuge to provide the appropriate g-levels demanded by
experimental designs. These specific tasks are defined below. Each
listing is preceeded by a code word which is our convenient local
designation. Of course the alphabetical listing does not imply
priority ordering.
(ADHCNT) Adapt the Arabidopsis Advanced Development Hardware
for use on the Centrifuge.
(AMYSED) Measure amyloplast sedimentation rate as influenced
by g-level.
(CIRCAD) Investigate the g-dependence of plant circadian
rhythms.
(CNTCLN) Describe the morphological development of plants at
different g-levels and on clinostats.
(CYTHST) Cytological and histological examination of plant
materials grown under different g-conditions.
(EPIFOG) Describe epinasty as a function of prevailing g-level.
(GXTRAP) Determine g-dependent morphological end points at several
g-levels and extrapolate to zero g.
(HYGCAP) With Biosatellite Pepper Plant hardware on the Centrifuge,
extend the tests of Expt. P-1017 to g-levels beyond 1.
(HYGWTR) With wheat seedling hardware from Biosatellite on the
Centrifuge, extend the tests of Expt. P-1096 to g-levels above 1.
(NULTST) Determine whether or not the physiology and development
of plants on clinostats depend on the prevailing g-level.
(NUTFOG) Determine whether circumnutation is a function of g-level.
(REVPOL) Determine the influence of g-level on the reversal of
polarity achieved by inversion of the plant axis in the g-field.
Much of the future research effort to be devoted to the above
tasks will be supported mainly by a contract (NAS 2-7730) and a grant
(NGR 39-010-149) to the University of Pennsylvania. Those aspects
which relate specifically to the use of the U.C.S.C. facilities will
be especially relevant to our continuing efforts under a grant to that
institution (NGR 39-030-010).
-10-
B. Accomodation of Visiting Investigators. When the Centrifuge
design and fabrication was authorized it was understood 
that the facility
would be shared with extramural projects should scientists from other
institutions wish to visit our laboratory for experiments which require
the application of sustained acceleration to their test materials.
Recently we became prepared to accomodate such guest investigators
and we have prepared a short brochure which describes our 
facilities.
Prior to the termination of the subject contract we have had one
inquiry from a potential guest investigator.
-11-
V. REPORTS AND MEMORANDA
The following reports and intramural memoranda are among 
those
generated by research on this project which have particular 
relevance
to recent work supported by the subject contract.
(1) Brown, A.H., Technical Status Report, Contract 
No. NASW -
2208, 4 pp. 29 December 1972.
(2) Brown, A.H., Variability of Arabidopsis 1 g A 
measurements
of morphological end points. Intramural Memorandum, 
5 pp. 23 May 1973.
(3) Brown, A.H., REVPOL observations from centrifuge 
test BCT-2/
050773. Intramural Memorandum, 7 pp. 22 August 1973.
(4) Brown, A.H., Condensed summary of centrifuge test, 
BCT-2/
050773. Intramural Memorandum, 5 pp. 30 August 1973.
(5) Brown, AH., Condensed summary of centrifuge test, 
BCT-1/
170573. Intramural Memorandum, 4 pp. 31 August 1973.
(6) Brown, A.H., Condensed summary of centrifuge test, 
BCT-3/
280873. Intramural Memorandum (in preparation).
(7) Brown, A.H,, Biocompatibility Test I--Advanced Development
Hardware for Arabidopsis satellite experiment, P-1003; 6-27 
June 1972.
Laboratory Report, 18 pp. 27 July 1972.
-12-
VI. PERSONNEL CONTRIBUTING DIRECTLY TO
THIS RESEARCH AT SOME TIME
DURING THE CONTRACT PERIOD
Dr. A.H. Brown, Coprincipal Investigator
Mr. D.K. Chapman, Research Specialist
Dr. A.O. Dahl, Coprincipal Investigator
Mr. WC. Ellenbogen, Facilities Manager
Mrs. M.S. Falk, Secretary-Technician
Mr. D.E. Keyt, Engineer
Mr. S.W.W, Liu, Research Specialist
Mrs. C. McCoy, Laboratory Technician
Mr. A.L. Venditti, Electronic Shop Engineer


Research on the effects of altered gravity and other factors on the growth and development of higher plants

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