symptoms whichaccompany poor root aeration of mesophytes are common Materials and methods ...

16 Pages·2006·1.63 MB·English

INFLUENCE OF SUBMERSION OF THE ROOTS ON TRANSPIRA-
TION, APPARENT PHOTOSYNTHESIS, AND RESPIRATION
OF YOUNG APPLE TREES
N. F. CHILDERS AND DAVID G. WHITE
(WITH NINE FIGURES)
Introduction
In spring there are often places in the orchard where water stands be-
neath the trees for a week or more. Within a short time the water recedes
and the soil appears to be properly drained for the remainder of the season.
The question arises as to the importance to the tree of these short periods of
excess-soil-moisture conditions, especially when the tree is in leaf. Ex-
periments are described in this paper in which transpiration, apparent
photosynthesis and, in some cases, respiration of young apple trees were
determined before and after the roots were submerged. In several experi-
ments the determinations were continued after the excess water had been
drained from the soil in order to ascertain how soon, if ever, the leaves
recovered in activity.
The literature pertaining to root submersion necessarily includes manv
studies in soil aeration. The well-known monographs by CLEMIENTS (6) in
1922, and CANNON (3) in 1925, summarize the work to that period. Certain
symptoms which accompany poor root aeration of mesophytes are common
knowledge. It is known that poor aeration will cause the foliag'e to wilt,
turn yellow, and die; theroots to develop slowly, become darker iu color, and
finally decompose; and the soil complex becomes depleted in oxygen and
higher in carbon dioxide. A proper aeration of the medium tends to
correct these faults (1, 5, 6, 7, 11).
Materials and methods
The Stayman Winesap variety was selected for these experiments be-
cause of its commercial importance and because it seems to be relatively
susceptible to the effects of soil water-logrging. The shoots used wvere grown
from two- and three-year stocks grafted on French Crab roots. Terminal
buds had set on all trees by the time tests were made, with the exception of
those shoots used in experiment VIII. The trees were potted in five-gallon
crocks orslightly larger wooden tubs and were grown in the greenhouse until
placed under test. A loam topsoil taken from an orchard was used for
potting. No attempt was made, however, to correlate the soil type with the
effects of root submersion. The term excess water, as used in this paper,
infers that water constantly stood above the soil surface. Check trees were
watered daily, or once every two days, in order to maintain the soil niear
603
Downloaded from on April 11, 2019 - Published by www.plantphysiol.org
Copyright © 1942 American Society of Plant Biologists. All rights reserved.
604 PLANT PHYSIOLOGY
field capacity. The HEINICKE-HOFFMAN (10) apparatus was employed for
measuring therates of transpiration and apparent photosynthesis or respira-
tion. Each determination lasted for a period of two and one-half hours.
Four series of experiments were performed in the environment-control
chamber (4) on a total of ten trees, and two series were performed outside
the greenhouse on a total of five trees. The temperature in the chamber
was nearly constant at levels of 800 or 850 F. The vapor pressure was
maintained near 16 mm. of Hg. Light averaged from 2,000 to 5,000 foot
candles at the surface of the leaves, depending on their distance from the
source. The temperature and relative humidity outdoors were averaged
TABLE I
INFLUENCE OF ROOT SUB-MERSION ON APPARENT PHOTOSYNTHESIS AND TRANSPIRATION\ OF
STAYMAANT WINESAP APPLE LEAVES. EXPERIMENT 8
APPARENTPHOTOSYNTHESIS TRANSPIRATION
PERCENT- PERCENT-
CO2/100 EXPECTED AGEOF H2O/100 EXPECTED AGEOF
DDAA.TSTEE,, C%.2/HOUR RATE EXPREACTTEED CM.2/HOUR RATE EXPRAETCETED
TEST TROL B X100 7788.5* 00 TEST TTRROOLL F X100 895tXlo0
A B C D E F G H
March 20 5.76 7.62 76 97 0.85 0.99 86 101
21 11.36 13.78 82 104 1.05 1.23 85 100
22 10.94 13.60 80 102 0.84 0.97 87 102
23 11.08 14.63 76 97 0.82 0.99 83 98
ROOTS SUBMERGED
26 9.94 13.90 72 92 0.91 0.91 100 118
28 9.79 12.19 80 102 0.76 0.88 116 136
30 11.42 13.78 77 98 0.99 1.04 95 112
April 1 13.43 16.05 84 107 1.11 1.29 86 101
3 13.75 17.79 77 98 1.08 1.28 84 99
4 12.82 15.82 81 103 1.01 1.09 93 109
6 11.43 13.78 83 106 0.94 1.32 71 84
8 14.67 14.67 100 127 0.84 0.87 97 114
10 12.28 13.94 88 112 0.87 0.84 104 122
14 11.09 14.78 75 96 0.89 0.87 102 120
16 8.33 13.20 63 80 0.69 0.70 99 116
18 8.19 12.07 68 87 0.58 0.71 82 96
20 5.92 11.72 51 65 0.59 0.69 86 101
22 4.80 13.78 35 45 0.41 0.80 51 60
24 3.08 14.31 22 28 0.33 0.73 45 53
26 2.47 13.42 18 23 0.25 0.75 33 39
28 0.35 11.42 3 4 0.13 0.75 17 20
30 1.92 12.09 16 20 0.12 0.70 17 20
May 2 0.00 11.38 0 0 __
..
* Average (78.5) of expected rate.
f Average 85.0 of expected rate.
Downloaded from on April 11, 2019 - Published by www.plantphysiol.org
Copyright © 1942 American Society of Plant Biologists. All rights reserved.
CHILDERS AND WHITE: S1JBMERSION 605
from three measurements at the beginning, middle, and end of each de-
termination. A sling psychrometer was used to determine the dew point
which was then converted to vapor pressure by use of psychrometric tables
(13). The average foot candles of light outside was calculated from the
records of a Micromax continuous recorder connected with a photoelectric
cell in the inmmediate vicinity of the trees. Supplementary experiments,
described later, were arranged in the greenhouse to make measurements of
leaf petiole angrles and to afford observation of root growth.
METHOD OF CALCULATION
The percenitage of the expected rate of apparent photosynthesis was cal-
culated as followvs: The average milligrams of carbon dioxide absorbed by
the proposed test leaves was divided by the average milligrams absorbed by
the check leaves. The quotients multiplied by 100 express the percentage
relationship between test and check leaves. The average of these per-
centages found before treatment began was then considered as 100 per cent.,
or that rate which the proposed test leaves would be expected to maintain if
they were not affected by the treatment. Thereafter, the percentage re-
lationships between test and check leaves were divided by the average per-
centage relationship of the pre-treatment period and multiplied by 100.
These products are plotted as percentages of expected rates for each experi-
ment. A typical set of data is presented in table I. Respiration and
transpiration were calculated in a similar manner.
Discussion of results
DESCRIPTIONS OF TREES USED IN CHAMBER
Symptoms of leaf injury which accompanied submersion of the roots
appeared on the lower leaves first and progressed acropetally. Abscission
of two or more lower test leaves often occurred before termination of an
experiment. In experiment I the leaves on the test tree developed light
green areas between the veins. The foliage wilted and drooped mostly from
the distal ends of the petioles. At the end of experiment IV the leaves on
test trees showed only a greater devlopment of anthocyanin pigments as
compared with the check leaves. No apparent differences in the foliage
occurred betwveen the test trees and controls in experiment V. The leaves
on the test trees in experiment VIII developed light green areas between the
veins. The foliage wilted and drooped (fig. 1) and finally appeared similar
to the treated tree in experiment I.
DESCRIPTIONS OF TREES USED OUTDOORS
Considerable tip and marginal burning had occurred within eight days
after flooding the roots of one tree outside in July (experiment II). The
Downloaded from on April 11, 2019 - Published by www.plantphysiol.org
Copyright © 1942 American Society of Plant Biologists. All rights reserved.
606 PLANT PHYSIOLOGY
leaves on a second tree of the same experiment only wilted and drooped,
similar to the foliage of the test tree in experiment I in the control chamber.
The leaves on trees having roots submerged from late September to late
October, experiment III, were slower in developing injury, probably because
of the cooler autumn temperatures. The lower leaves showed yellowish-red
FIG. 1. Roots of the tree on the left were submerged in water for 45 days in the
enivironiment-control chamber. Tree on the right was watered every second day. Both
trees were of equal vigor at the outset. See figure 8 for comparison of transpiration and
apparent photosynthesis.
Downloaded from on April 11, 2019 - Published by www.plantphysiol.org
Copyright © 1942 American Society of Plant Biologists. All rights reserved.
CHILDERS AND WHITE: SUBMERSION 607
splotches which finally became necrotic. The blades curled upward at the
margins but did not droop. At the end of the experiment the upper leaves
appeared similarto theupper leaves ofthe check tree except for the presence
of considerable anthocyanin pigments. The symptoms of leaf injury which
appeared in these experiments were similar to descriptions given by
HEINICKE, et al. (9) for orchard trees purposely flooded.
EXPERIMENT I. PHOTOSYNTHESIS AND TRANSPIRATION
Experiment I was conducted in the chamber at a temperature of 85° F.
Six comparable leaves on each of two trees were selected for study. The
roots of one tree were constantly submerged beginning June 22, 1940. The
percentages of the expected rates of apparent photosynthesis and transpira-
tion are plotted in the upper graph of figure 2. The points oni the chart
EXPERIMENT I
110
-1-..0.... A
75
05 WAETXECRESSADDED
U
H25POTOSYNTHESIS
--TRANSPIRATION
U0 22 24JUNE26 28 30 12940 4 6 8 K e JU4LY 16 e8 2 22
llI 11,
',~*~~~~~N~-1
75 75 1
. N.
:~ ~
LIC
r
5 WArERADDED\ a 50 WAETXECRESASDDED WAETXECRESSREW40VFD
- \
X; PHOTOSYNTHESIS X25-PHOTOSYNTHESIS
--TRANSPIRATION --TRANSPIRATION
TREE-A- TREE -B-
9n ,, 1J3ULY ,-5 17 19 9 , 13 15 JU17LY 19 21 23 25
EXPERIMENT 1
FIG. 2. Ilnfluence of submersion of roots on apparenit photosylnthesis anid transpira-
tionl of apple leaves. Expressed as percentage of expected rate. Horizontal line at 100
represents photosyntliesis anid transpiration of check leaves. Experiment I was performed
in environment-control chamber; experiment II was out-of-doors.
during the pre-treatment period exemplify the usual variation in activity
of the test leaves as compared with the check leaves. Both apparent photo-
Downloaded from on April 11, 2019 - Published by www.plantphysiol.org
Copyright © 1942 American Society of Plant Biologists. All rights reserved.
608 PLANT PHYSIOLOGY
synthesis and transpiration gradually decreased to between 80 and 70 per
cent. within the 30-day period of submersion.
EXPERIMENT IL PHOTOSYNTHESIS AND TRANSPIRATION
Experiment II was performed on two test trees and a check tree placed
outside of the greenhouse in July, 1940. Four comparable leaves were used
on each tree. The results are shown as percentages in the lower two graphs
offigure 2. Therates ofphotosynthesis andtranspiration of test tree A had
decreased to 25 per cent. seven days after the flooding period started on July
13. Extreme foliage injury occurred and prevented further measurements
EXPERIMENT m
130
¢> < ~~~~~~~~~PHOTOSYNTHESIS
z= ~ ~~~~q~~~-~TR~AN~SP~IR~ATION
SE OCT
w ?~~~~I
iQfi020'P*A HOTIOSYN0THESIS
z TREE--A
w -~~~~~~~~~~~PHOTOSYNTHESIS
8T0R-EBEx-m ~ ~ ~ ~ --TRANSPIRATION
C~~~2~3~~2~5~ 27 9 1 34 7 9 19 21 23
SePT OCT
W40
20
I23 25 27 29 1 3 5 7 9 II 13 15 I7 19 21 2
SPT 190OCT
FIG. 3. Apparent photosynthesis and transpiration of trees A, B, and a in experi-
ment III. Note differences in individual tolerance of trees to root submersion. Experi-
ment performed out-of-doors.
Downloaded from on April 11, 2019 - Published by www.plantphysiol.org
Copyright © 1942 American Society of Plant Biologists. All rights reserved.
CHILDERS AND WHITE: SUBMERSION 609
on this tree. The apparent rates of photosynthesis of test tree B decreased
to 67 per cent. during the sameseven days of submersion, while transpiration
decreased to 69 per cent. The soil of tree B was drained of free water after
nine days of submersion; six days later the rates of leaf activity of the test
tree were equivalent to its pre-treatment period.
EXPERIMENT III. PHOTOSYNTHESIS AND TRANSPIRATION
Experiment III was conducted outside the greenhouse dcuring late
September and through most of October, 1940. The roots of three trees
were submerged on September 29 and a fourth tree was used as a check.
Three comparable leaves were used on each tree. The percentages of ex-
pected rates of apparent photosynthesis and transpiration are given in
figure 3. Both processes ultimately were severely reduced, with photo-
synthesis less than 10 per cent. of its expected rate. The time of lowest leaf
activity varied with individual trees. The roots of the trees were washed
free ofsoil atthe end ofthe experiment. Several short, rather stubby, white
roots had developed on or near the graft union of the flooded trees.
EXPERIMENT IV. PHOTOSYNTHESIS, TRANSPIRATION, ANDSTOMATAL ACTIVITY
Experiment IV consisted of two test trees and a check placed in the
chamber at 800 F. Four leaves on each tree were used; the results are
plotted in figure 4. As much as a 96 per cent. reduction in apparent photo-
synthesis of test tree A and a 79 per cent. reduction in test tree B were
associated with submersion of the roots. Transpiration rates were reduced
also but not so severely. The free water was drained after 18 days of
flooding, and within 4 to 6 days there was a trend toward recovery in leaf
activity. The leaf activity of tree A did not completely recover by the end
of the experiment. Transpiration of treeB evidently recovered while photo-
synthesis continued between 85 and 100 per cent. of its expected rate. The
roots were washed free of soil at the end of the experiment, 14 days after the
excess water had been drained. Roots of the test trees were scanty as com-
pared with those of the check tree. The test roots were also darker in color
than the checkroots; no other differences were visible.
In experiment IV stomatal activity of the leaves under study was ob-
served through a Leitz "Ultrapak" microscope. The study was made on
November 22, 23, and 24, when leaf activity had become low ow-inog to ex-
tended root submersion. The counts recorded in each observation were an
average from a part of three fields near the apex of a leaf. Each count
included an observation of 25 to 40 stomata. Any stoma which did not
appearto be completely closed was recorded as open. No attempt was made
to note differences in degree of opening since there appears to be no positive
method of knowing when a stoma is partly open or closed. The data are
Downloaded from on April 11, 2019 - Published by www.plantphysiol.org
Copyright © 1942 American Society of Plant Biologists. All rights reserved.
610 PLANT PHYSIOLOGY
plotted in figure 5 as percentage of stomata open. There were no consistent
differences between the activity of stomata of treated and check trees.
Hence, the marked reductions in photosynthesis and transpiration (fig. 4)
could not be correlated with stomatal activity during this 3-day period.
EXPERIMENT IZ
TREE-A-
128. ON FOUR LEAF ONFCURLEAF BASIS ON TFREE LEAF BASIS
TREE-B-
NOV 1940 DEC
FIG. 4. Transpiration and apparent photosynthesis of test trees A and B in experi-
ment IV. Soil was flooded on November 9 and drained 17 days later.
EXPERIAIENT V. PHOTOSYNTHESIS, TRANSPIRATION, RESPIRATION, AND
LEAP TEMPERATURE
Experiment V was conducted with two trees in the chamber at a tem-
perature of 850 F. This experiment was designed to measure any differ-
ences in the activity of upper leaves as compared with middle leaves on a
shoot with submerged roots. The experimental leaves were large and ma-
ture. Afewofthebasalleaves of each treeyellowed and abscised soon after
being placed in the chamber. Three of the top-most leaves which would fit
the leaf-cups were used to compare with three leaves located approximately
at the middle of the shoots. The shoots were about five feet in height. Ap-
Downloaded from on April 11, 2019 - Published by www.plantphysiol.org
Copyright © 1942 American Society of Plant Biologists. All rights reserved.
CHILDERS AND WHITE: SUBMERSION 611
z
0
!-
2
0
U)
hJ
B.
z
I~-
z
aU:
L;
FIG. 5. Stomatal behavior of test and control leaves from November 22 to 24, inclu-
sive, experiment IV. During this period apparent photosynthesis and transpiration were
showing reductions of 20 to 95 per cent., 13 days after beginning submersion.
Downloaded from on April 11, 2019 - Published by www.plantphysiol.org
Copyright © 1942 American Society of Plant Biologists. All rights reserved.
612 PLANT PHYSIOLOGY
parent photosynthesis and respiration were measured on alternate days.
The respiration determinations began about 6:00 P.M., when the chamber
was darkened. Transpiration was measured in all determinations.
The apparent photosynthesis and transpiration of the test tree in ex-
periment V are shown in figure 6. In the upper leaves the trends of both
EXPERIMENT v
UPPER LEAVES
oW . *.
PHOOSYNTHESIS -:
TRANSPIRATION--:
us MIDDLE LEAVES
A91FB
a1.0~0 JAN
i 0 12 12b2 8^2 24 28v28 0 9 ii 5' 17 19 2
FIG. 6. Transpiration and apparent photosynthesis of upper and middle set of leaves
on one-year tree in experiment V. Roots were submerged on January 16; water was
drained on February 9.
processes were similar, showing 30 to 50 per cent. reductions throughout the
25-day period of submersion. Removal of the excess water was followed by
apparent recovery in leaf activity. The photosynthesis of middle leaves was
not consistently less than the expected rate after submersion, although an
average of the twelve determinations for the period would fall well below the
100 per cent. line. Nevertheless, it appears that photosynthesis of the
middle set of leaves was not affected as much as that of the upper set.
Transpiration of middle leaves showed a reduction similar to that which
occurred in the upper leaves.
Respiration and transpiration, as determined at night, are plotted in
figure 7. It should be emphasized that the amount of carbon dioxide re-
leased by the leaves was relatively small, and the possibility of error in
procedure could be somewhat greater. As shown in the graph, however,
the trends were reasonably consistent from day to day. Apparent respira-
tion after submersion was definitely increased in both upper and middle
leaves. Indeed, on some days respiration of test leaves was almost double
Downloaded from on April 11, 2019 - Published by www.plantphysiol.org
Copyright © 1942 American Society of Plant Biologists. All rights reserved.