THE NUTRIENT-ELEMENT BALANCE OF THE TOMATO AND ITS SUSCEPTIBILITY TO PHYTOPHTHORA INFESTANS AS AFFECTED BY TWO LEVELS OF ZINC

41 Pages·01.763 MB·English

by  SMITH, CYRIL B.

DOCTORAL DISSERTATION SERIES
TtfE M W tEM T~£UM ENT SALM Q £ OF W £
t i t l e
TOMA TP M d ITS S lf$t£P T /S /L )T Y TO PttYTOPMTMOKA
//Y&STAMS AS AFFGtTEd BY TWO LEVELS OF 2JAI&
Cf&JL 6SVE&L&Y SMITH _______ _
AUTHOR
flSAtM. ST &0LL*
UNIVERSITY DATF / f f l
0k. P. 99
DEGREE PUBLICATION NO. _
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I T M UNIVERSITY MICROFILMS
L L P S ANN ARBOR . MICHIGAN
The Pennsylvania S tate College
The Graduate School
Department of H o rticu ltu re
THE NUTRIENT-ELEMENT BALANCE OF THE TOMATO AND ITS SUSCEP­
TIBILITY TO PHYTOPHTHOBA INFESTANS AS AFFECTED BY
TWO LEVELS OF ZINC
A D isse rtatio n
by
C yril Beverley Smith
Submitted in p a rtia l fu lfillm e n t
of the requirem ents
for the degree of
DOCTOR OF PHILOSOPHY
February, 1950
Approved:
fLO /itso
P rofessor of P lant N utritio n
Ifsro
Head, Department of H o rticu ltu re
ACKNOWLEDGEMENTS
The author is g reatly indebted, to Dr* W alter
Thomas fo r h is continued encouragement and advice
during the course of these stu dies and in prepar­
a tio n of the m anuscript; and also to Dr. Warren B.
Mack fo r h is co-operation and sincere in te re s t.
Special ap p reciatio n is extended to Dr. W. B.
M ills of the Department of Botany fo r supplying
cu ltu res of Phytophthora in festan s and suggesting
the in o cu latio n procedure.
Thanks are also due Miss M arguerite D esaul-
n ie rs fo r capable assistan ce in the chem ical anal­
yses and Mr. George A. Taylor fo r valuable help
w ith the in o cu latio n s.
^•*3*
CONTENTS
Page
INTRODUCTION ................................ 1
MATERIALS AND EXPERIMENTAL PROCEDURES ..................... 4
N utrient C ulture Assembly .................. 4
N utrient S olutions ................................. 6
P lan ts ..................................................................... S
Leaf Samples ...................................................................... 3
Chemical A n a ly se s........................... 9
In ocu lation s ....................................... 12
P relim inary Experiment .......................................... 13
Experiment 1 ................. 14
Experiment 2 ................. 15
EXPERIMENTAL DATA AND RESULTS ........................................ 16
P relim inary Experiment ............... 16
Experiment 1 ...................................................................... 19
Experiment 2 .................................. 23
Experiments 1 and 2 (Combined) ......................... 23
DISCUSSION..................................................................... 29
SUMMARY AND CONCLUSIONS ....................................................... 33
LITERATURE CITED ......................................................................... 35
1
- -
INTRODUCTION
This fundam ental study deals w ith the re la tio n sh ip
between zinc n u tritio n of tomato p la n ts and s u s c e p tib ility
to Phytophthora in fe sta n s causing Late B lig h t. S tudies
on the re la tio n sh ip between n u tritio n of p la n ts and sever­
ity of d iseases have in d icated th a t n u tritio n is one of
the fa c to rs which has a m easurable e ffe c t upon the course
of d isease developm ent. Since f e r tili z e r treatm ents and
environm ental conditions a ffe c t sp e c ific ho st p la n ts and
pathogens d iffe re n tly , i t is im portant to o b tain p recise
knowledge of the re la tio n sh ip s between these fa c to rs .
Most of these in v e stig a tio n s (11, 23, 24, 25, 28, 29,
30, 31, 32, 33, 34, 35)* have d e a lt p rin c ip a lly w ith the
th ree f e r t i l i z e r elem ents, n itro g en , phosphorus and potas­
sium. In general, high n itro g en ap p lica tio n s have in ­
creased the s u s c e p tib ility of p lan ts to disease organism s,
w hile high potassium ap p lica tio n s have increased the p la n ts ’
re sis ta n c e , but re s u lts have been in c o n siste n t in several
cases. These stu d ies have not included le a f analyses so
th a t th e ac tu a l n u tritio n a l sta tu s of the p lan ts was not
taken in to co n sid eratio n . At tim es, n u tritio n seemed to be
re la te d to the vigor of the p lan ts but sev eral oth er fa c to rs
unquestionably were involved.
With few exceptions, the workers 3ust c ite d have not
concerned them selves w ith th e m icro n u trien t elem ents.
- 2 -
There is good reason to b eliev e th a t these elem ents play an
im portant ro le in the s u s c e p tib ility of a p lan t to a path­
ogen* One of the e s se n tia l m icronutrient elem ents which
would seem to be very im portant in th is re la tio n sh ip is
zinc which is considered e s s e n tia l also to the growth of
fungi (12)* The zinc requirem ent of the fungus may be
q u ite d iffe re n t from th a t of the h o st.
L ittle is known about the physiologic ro le of zinc in
the p la n t except th a t zinc and copper act as a p a ir of
m utually coordinating c a ta ly sts in o x id atio n -red u ctio n re ­
actio n s (26). I t is thought th a t zinc plays a very im­
p o rtan t ro le in re s p ira tio n probably by en terin g in to the
m olecule of the enzyme, carbonic anhydrase, which catalyzes
the re v e rsib le re a c tio n of carbonic acid to carbon dioxide
and w ater. This enzyme has been found in anim als and was
iso la te d from eld erb erry leaves by Day and F ran k lin (5).
Compounds containing zinc are being used in creasin g ly
as fu n g icid es. Zinc ethylene bisdithiocarbam ate (Zineb)
has been found e ffe c tiv e in c o n tro llin g Late B ligh t (Phyto-
•phthora in fe sta n s) and E arly B light (A lte rn a ria so lan i) of
the tom ato. That th e zinc is absorbed by the p la n t when
th is compound decomposes was shown by Emge and Linn (8) .
M oznette e t a l. (19) rep orted th a t when pecan tre e s
showed symptoms of ro s e tte caused by zinc d eficien cy they
were much more severely attacked by two fungi causing Leaf
B lotch (M ycosphaerella dendroides) and Brown Leaf Spot
- 3 -
(Cercospora fu s c a ). When the ro se ttin g was overcome by
treatm ent w ith zinc s u lfa te , th ese d iseases became le ss pre­
v alen t or disappeared e n tire ly . This is a case where para­
s it ic fungi became a minor problem when the tre e s were pro­
p erly nourished. The leaves of pecan tre e s showing symp­
toms of ro s e tte have been found to have a much lower zinc
content than those of h ealth y tre e s (9, 10). Thus, higher
zinc co n cen tratio n in the leaves was co rrela ted w ith r e s is ­
tance to disease organism s.
M illikan (17) found th a t s o il ap p licatio n s of zinc
s u lfa te , e sp e c ia lly on areas carrying the g re a te st in fe s ta ­
tio n of ro o t ro t fungi (Helminthosporium spp ., Fusarium
spp. and o th ers) re su lte d in very su p erio r growth and in ­
creased y ield s of wheat and o a ts. The evidence in d icated
th a t zinc su lfa te treatm ents a ssiste d p la n ts in w ithstand­
ing the d e le te rio u s e ffe c ts of these m icroorganism s but i t
is not known w hether th is e ffe c t was due to the zinc su l­
fa te a ffe c tin g the n u tritio n a l sta tu s o f the p la n ts or by
sim ply actin g as a fu n g icid e.
- A -
MATERIALS AND EXPERIMENTAL PROCEDURES
R utgers tomato p la n ts were grown in greenhouse n u tri­
ent c u ltu re s containing d iffe re n t le v e ls of zinc, the con­
ce n tra tio n s of a l l the o th er elem ents being kept con stant.
Since as wide a range of zinc concentrations as p ossible
was d esire d , two le v e ls of zinc were used, one as low and
th e oth er as high as p o ssib le w ithout producing d eficiency
or to x ic ity symptoms re sp e c tiv e ly . These two c r itic a l
le v e ls were determ ined in a prelim inary experim ent.
Follow ing the com pletion of the prelim inary experi­
ment, two se ts of p la n ts were produced, designated in the
follow ing as Experiment 1 and Experiment 2 re sp e c tiv e ly .
S everal sp e cia l techniques and precautions were employed
to m aintain the zinc concentrations as sp e c ifie d . At the
f r u it- s e ttin g stag e, the p la n ts were inoculated w ith a
c u ltu re of the tomato race of Phytouhthora in festan s
(Mont.) Deby. Six days la te r a d isease index was calcu­
la te d by m easuring the spread of the fungus. Leaf samples
were taken 3u st p rio r to the tim e of the in o cu latio n s and
analyzed fo r fo u rte en elem ents to determ ine the n u trie n t-
elem ent balance of th e p la n ts. The combined re s u lts were
te ste d fo r s t a tis t ic a l sig n ifican ce by the ”t n te s t (13).
N u trien t C ulture Assembly
The n u trie n t c u ltu re equipment used in these experi-
- 5 -
ments was sp e c ia lly constructed fo r research w ith micronu­
tr ie n t elements* In se ttin g up th is equipment, the problem
of zinc contam ination was considered c a re fu lly . A ll so lu ­
tio n s came in contact w ith pyrex glass and p a ra ffin only,
both o f which were fre e from zinc.
F o rty -eig h t f o u r - lite r pyrex beakers were used as con­
ta in e rs fo r th e n u trie n t so lu tio n s. Each beaker was f itte d
w ith an ae ra to r constructed from pyrex tubing and a pyrex
f r it te d d isc . Both the beakers and ae ra to rs f i r s t were
cleaned thoroughly w ith concentrated aqua re g ia . W ater­
proofed pasteboard cy lin d ers were placed around the beakers
to keep out lig h t. Covers were prepared from tw elve-inch
asbestos board squares in th e cen ter of which th ree -in c h
corks w ith one-inch holes were placed. Pyrex tubes were
attached to the covers in such a way as to support the ro o ts
of the p la n ts. The com plete covers were coated w ith high
m eltin g -p o in t p a ra ffin .
The co n tain ers were s e t on two p a ra lle l wooden benches
in four rows of tw elve each. A su p erstru ctu re was b u ilt
over th e benches from which stakes fo r supporting the p lan ts
were suspended. This also provided a framework fo r th e
parafilm te n t used in m aintaining a high re la tiv e hum idity
about the p lan ts during th e in o cu latio n s.
Main a irlin e s down the cen ter of each bench were con­
stru c te d of g lass tu bin g. The in d iv id u al ae ra to rs were jo in ­
ed to th ese w ith sh o rt p ieces of p la s tic tubing around which
clamps were attached fo r co n tro llin g the flow of a ir .
N utrient S olutions
In a l l th ree experim ents described the same basic n u tri­
ent so lu tio n was used; only the le v e l of zinc was v aried .
The concentrations of the oth er elem ents were kept as con­
sta n t as p o ssib le. A pH of 6.0 was m aintained in a l l the
so lu tio n s.
A fo u r-s a lt so lu tio n , commonly known as Hoagland*s #1
n u trie n t so lu tio n supplied the m ajor elem ents, w hile the
m icro n u trien t elem ents other than zinc were added in minute
q u a n titie s by th e use of a minor stock so lu tio n as described
by Hoagland and Arnon (1-4) - The com position o f the basic
n u trie n t so lu tio n is shown in Table 1. This gave the follow ­
ing concentration s (p .p .m .): N, 210; P, 31; K, 234-5 Ca, 200;
Mg, 4-9; S, 64.; E, 0 .5 ; Mn, 0.5; Cu, 0.02; and Mo, 0.01.
Iro n was supplied as 0.5 per cent ferro u s su lfa te a t the
ra te of one m i l lili te r per p lan t and was added tw ice weekly.
Zinc was added in the various q u a n titie s requ ired from stock
so lu tio n s of zinc su lfa te (ZnS0^ .7H20) which contained 50 or
500 p.p.m . zin c. Cobalt was not in te n tio n a lly supplied in
the n u trie n t c u ltu re s.
Both the chem icals and w ater used were h igh ly p u rifie d
to prevent contam ination w ith zinc. The m etal im p u rities
were removed from the four main s a lts by a procedure in v o l­
ving p re c ip ita tio n and adso rption a t a high tem perature and