PLANT SCIENCE BULLETIN a Publication of the Botanical Societyof America, Inc
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PLANT SCIENCE BULLETIN A Publication of the Botanical Societyof America, Inc. VOLUME 4 DECEMBER. 1958 NUMBER 6 A Mobile DesertLaboratory F. W. WENT Many physical. chemical. and biological problems can plans could be realized and in the autumn of 1956 the be solved in our standard laboratories where materials first trial runs were made. In the intervening 2 years --- and ~~e!im':.ntal~ methods can be brought together. A the laboratory has proven its effectivenessand now a number ototner problems. however. reqUlre tor thetr shortdescnpfion6f Its faClhtles can-De gtVen~--~ - solution observations in nature or require materials For precise physiological measurements laboratory which are available only in special locations. This is space is provided in a 24-ft. trailer. The utilities for particularly true for ecological problems where plants this trailer laboratory are provided in a 5 ton truck. In and animals have to be studied in their natural habitat its body are mounted: in relation to the environmental factors which exist in particular localities. This is also true when studies have 1) a 2~00 liter water tank which can be pressurized to be made on old plant specimenswhich could not be as high as 12 atmospheres. produced of sufficient age in the laboratory. Perhaps 2) a 6 kilowatt motor generator with good frequency most unique are the requirements for studying desert and voltage control. This generator usesapproxi- ecology. A considerable number of the most extreme mately I gallon of gasoline per hour and there- desert plants have very extensive root systems which fore with its 5 gallon tank capacity has to be re- could not be reproduced in any laboratory of reasonable filled every 5 hours. dimensions. 3) a 70 gallon gasoline tank which can be brought During the last fifteen years I had been studying prob- under pressure. lems concerning desert plants. I found that their germi- 4) an air compressor providing pressure for both nation occurred only under very special conditions which the water and gasoline tanks. and for inflating did not prevail every year and very often did not occur in tires. the same locality mo.re.than ~>nc~every five to teD;years. 5) storage casesfor tools. plant presses.and other The first stage of this mvestigatlOn could be earned out necessarybulky equipment. through simple observation and counting in the field and was accomplished on frequent weekend desert trips. ~his tr~ck is covered wit~ a taI1?aulin and it. has a Inevitably a stage was reached in which more precise sp~Clally remforced rear housmg w~lch can take It over measurementsand experiments were required for which fairly rough roads. It would be desirable to have a four- more elaborate equipment was necessary. Therefore. wheel drive .truck to give it better traction in sandy places this desert research had outgrown the family car and where occasIOnally measurementshave to be made. the improvised camping site. An ordinary. stationary. The trailer was originally a house trailer which has laboratory could not accomplish desired ends since only been rebuilt to provide the necessarylaboratory facilities. infrequently conditions proper for the investigations The rear end has a low bench across the back which is would occur in the immediate neighborhood of such a of proper height for microscopic work. Both a binocular stationary laboratory. Probably this has been one of and a regular microscope are available. plus a set of the main difficulties in connection with the Desert Lab- reagents. slides and tools to make microscopic sections. oratory of the Carnegie Institution of Washington in A folding table leavesenough spacefor two investigators Tucson. which was abandoned 20 years ago. to work in this rear end. A small library of floras and To overcome the problems of a fixed location. a mo- faunistic literature is available for convenient reference. bile desert laboratory was designed. partly on the basis In the rear end .are also mounted a desert.cooler which of the car park of the Land Researchand Regional Sur- can' keep the trader very ~om~ortable.e.ven m the hottest veys Division of the Commonwealth Scientific and In- weather. and a less effective au-conditioner. dustrial Research Organization in Australia and partly The front end. equipped for physical and chemical on the truck-based ecological laboratories which had work. is separatedfrom the rear by a short corridor. on been surveying the Sahara desert. Through the gener- one side of which there is a wash room and shower. plus osity of Mrs. Pearl McManus of Palm Springs these storage space for microscopes. balances and further PAGE TWO PLANT SCIENCE BULLETIN Plant ScienceBulletin is shut off the rate of transpiration can be calculated quite HARRIET B. CREIGHTON. Editor easily. Department of Botany and Bacteriology It is very difficult to make theseplastic containers with Wellesley College. Wellesley 81. Massachusetts the enclosed branch and fan shaft completely air-tight but by measuring accurately the amount of air which is EDITORIAL BOARD pulled from the chamber the air renewal rate can be George S. Avery, Jr Brooklyn Botanic Garden measured. In this caseoutside air is used to make up the Harlan P. Banks Comell University air withdrawn from the container by suction. If air of Harriet B. Creighton Wellesley College a known CO2 content has to be introduced into the con- Sydney S. Greenfield Rutgers University Paul B. Sears. Yale University tainer the presenceof leaks is again inconsequential if air samples are withdrawn from the container at a rate DECEMBER. 1958 . VOLUME4. NO.6 smaller than what is being introduced. Manifolds have been installed to connect containers enclosing different equipment. and on the other side. cupboards and an plants in successionwith the CO2 analyzer. An auto- electrical refrigerator. A four burner gas stove with matic valve and switch system provides a means to oven and a gas heater are both operated with butane gas. switch automatically from one container to the other The samegas can be used for bunsen burners. A double and to record behavior of five different plants. sink can be used both for washing and for laboratory In a more recent modification of the apparatus by Mr. needs and is provided with a direct connection to the G. Durdle the measurementof the transpiration has also water tank in the truck and thus provides plenty of run- been made automatically recording. To this end a fast ning water. A 6 gallon electric water heater provides a stream of dry air is introduced by opening a magnetic limited amount of hot running water. Cooking utensils. valve into the plant container. This air dries out the food and dishes are stored above and below the sink. container to a pre-set point, e.g., 30% r.h. Then the stove and refrigerator in cupboards. Along one side and magnetic valve is closed, and the humidity in the con- in the front of the forward compartment are high bench- tainer increases through transpiration of the branch. es with drawers underneath in which laboratory glass- When the humidity has reached40%, the magnetic valve ware. corks. tubing. etc.. is stored. Along the other side opens again, the air in the plant container is dried to a couch occupiesthe forward compartment. 30%, etc. These changes in humidity are recorded, and The main problem at present under investigation in from the record the rate of humidification, indicating the Mobile Desert Laboratory is a study of transpiration. transpiration, is read. photosynthesis. and respiration of desert plants. A few The equipment just described has already allowed the annuals have been investigated but the main effort is establishment of the existence of exceedingly high DPD concentrated on the study of more specialized desert in one of the most extreme xerophytes of the California shrubs which are able to grow under extreme drought deserts,Peucephyllum schottii. It also has becomeestab- conditions. To this end a Liston-Becker CO2 analyzer lished that under drought conditions both transpiration has been installed which operates on the power supply and photosynthesis may occur for a short time in the from the motor generator in the truck. The power sup- morning and late afternoon stopping during the mid- ply for this CO2 analyzer goes through an extra voltage dle of the day. The same branch after sufficient rain regulator but unfortunately any considerable change in will continue both transpiration and photosynthesis load on the generator changes the frequency sufficiently throughout the day. that. the readings of the analyzer change. Tl1etefore"a ~Jthou&h it.is .not too eaH to pull the .laboratory off separate power source should be installed for the CO2 the roads there are sufficient smalfroads 1n the desert to analyzer. At present all intermittent power consumers reach almost any plant or plant community which such as the air compressor. water heater and refrigerator should be measured. Setting up of the trailer, making have to be disconnected as long as CO2 measurements all water and electrical connections, and making the lab- are being carried out. Continuously operating equip- oratory ready to operate takes two people 30-60 minutes. ment such as lamps and the desert cooler can be left on A canvas canopy can be installed along one side of the without influencing CO2 readings. A Leeds ~ Northrop Laboratory, providing shade and living space for the Type H Speedomax records the readings of the CO2 ana. personnel. Several tables and chairs are carried at all I yzer. times. Upon arrival at the desired locality, a rather level Photosynthesis is measured by enclosing a branch in spot is selected,not too sandy, and in close proximity to a plexiglass container which has a fan mounted inside the plants to be measured.