Boron Tolerance of Sugar Beets in Relation to the Growth and ... - Vol

Boron Tolerance of Sugar Beets in Relation to
the Growth and Boron Content of Tissues
JAMES VLAMIS AND ALBERT CLRICH i
Receivedlor publication March 2,1973
The extensive work of Eaton (4)2 established sugar beet plants as
having a high requirement for boron and a high tolerance for boron
excess. His work and that of others indicates that plant tissues in the
deficiency range tend to run about 10 to 35 parts per million boron (1,
7, 12).
In the toxic range Eaton showed that the tops and laminae ofsugar
beets could contain hundreds of ppm B without affecting yield very
markedly.
This work presents the results of experiments designed to study
the growth o[ sugar beets in solutions o[ high concentrations of Band
to correlate growth with the B content of selected tissues. A previous
report covered the B nutrition of sugar beets in the deficiency range
(12).
Plant culture
Materials and Methods
Sugar beet seeds were planted in vermiculite and irrigated with a
nutrient solution containing 0.25 ppm B (Table 1). The seeds used
(F58-554H I-MS of NB 1 X NB4) were previously treated with a fungicide,
Phygon XL, at a rate of 1 gram per 100 grams of seed.
Eighteen days later the seedlings were each wrapped with Dacron
fiber and transferred to cork rings. Three seedlings were placed in
Table l.-Chemical composition of nutrient solution added at two intervals.
Salts added, meq/l Microelements, mg/l
Ca(N03), 5.0 Mn , as MnSO,· 4 H,O 0.25
KN03 2.5 Ln, as ZnSO, . 7 H,O 0025
MgSO, 2.0 C u, as CuSO, · 5 H2O 0010
KH,PO, 1.0 Mo, as Mo03 0.005
K,SO, 0.5 Fe,asEDTA 2.5
NaCI 0.5 Boron (see Tabk 2)
1 Plant Physiologists, Department ofSoils and Plant Nutrition, University ofCaJifornia, Berkeley.
'Numbers in parentheses refer to lit erature cited.

VOL. 17, No.3, APRIL 1973
281
perforated masonite covers mounted on 5-gallon cans painted with
aluminum paint on the outside and Amercoat No. 33 on the inside.
The masonite lids were painted with aluminum on the upper surface
and Valspar underneath. The containers were filled with nutrient
solutions with compositions as given in Table 1.
Boron was added to the solutions so as to give the following range
ofB in ppm: 0.5, 2,4,8,16,32,64, and l28 (Table 2). In two of the
experiments a 1 ppm B solution was included. Three replicates ofeach
rate were set up. The experimental period for the main experiment
extended from April 26 to June 8. Midway in this period another dose
ofnutrients was added to each pot, but without a further addition ofB.
The test was conducted in a smog-free clear glass greenhouse. The
nutrient solutions were kept at a pH of 5.0 to 6.5, and distilled water
was added as needed.
Harvesting
The plants were harvested 6 weeks after transplanting. Fresh
weights were taken of the shoots and roots separately. The leaves were
divided into three age groups-young, mature, and old. Leaves which
had not reached full development were classified young, and those
showing signs of senescence were placed in the old category. The
intermediate leaves were called mature. The leaves were then separated
into blades and petioles for boron analysis. The residue consisted
of dead or wilted leaves. The fibrous roots were removed from the
storage root, centrifuged to remove free water, and fresh weights
taken.
Preparation of samples and chemical analysis
The plant parts were placed in paper bags and dried at 70°C in a
forced-draft oven for 72 hours. The dried material was weighed,
ground in a Wiley mill with a 40-mesh screen, and stored in plastic vials.
The samples were analyzed for boron at room temperature by the
curcumin method, using an acetate buffer (6). All other analyses were
made by established methods (2, 8). .
Boron excess and yield
Results
The data obtained are shown in Table 2 and figure 1. The growth
curve for the tops shows that maximum yields were obtained at 0.5, 2,
4, and 8 ppm B in the external solution . This is followed by a steep drop
at 16 ppm and then a more gradual decline in yield for the remainder
of the curve. The beet curve follows the one for the tops except for a
small shift to the left. Thus, the first significant drop in beet yield occu rs
at 8 ppm as opposed to 16 ppm for the tops. The fibrous root response
resembles very closely that of the tops.

284 J OC R:-;AL OF TH E A. S. S. B. T .
Figure 2.-0n the left, leaf series of one plant grown in 64 ppm B
showing severe symptoms on old leaves. On the right, closeup of second
oldest leaf with severe symptoms of B toxicity.
>-
0::
o
10 -
- 0 YOUNG BLADES
-0 MATURE BLADES
--x OLD
BLADES
L L L L
600 1200 1800 2400
PPM BORON IN BLADES
Figure 3.-Relation of top dry weights to boron content of young, mature,
and old blades.

VOL. 17, No.3, APRIL 1973 287
closer to 16 ppm. This puts the sugar beet plant in the category of
plants tolerant of excess B in comparison with many cultivated plants
(11). In the extensive work by Eaton (4) several varieties of sugar beet
were all found to be fairly tolerant of high B in the external solution. A
recent study by EI-Sheikh et al., (5) showed that cucumber, squash,
melon, and corn had a 50% reduction in growth with 6,12,12, and 16
ppm B in solution, respectively.
In the case ofsugar beets the focus has to be on the beet root more
than on the shoot. The first suggestion of a significant decrease in beet
yield is at 8 ppm B. The tissue analysis, however, shows that there was
very little B accumulation in either the beet or the fibrous roots.
Therefore, the reason the beet yield dropped at a lower B concentration
than the tops must be an indirect one. The photosynthetic rate
must be adversely affected before the yield ofthe shoots is decreased so
that there is enough sugar manufactured for the growth of the tops
and fibrous roots but not enough for the storage root.
The boron analysis of the tissues indicates that the yield and the
appearance of the leaves are not affected until the B content of the old
leaves reaches 600 ppm. At the same point the mature leaves have 450
and the young leaves 300 ppm, both without symptoms. Brandenburg
showed that B content increases with the physiological age of the
tissues (1) . In this instance, since the injury first affects the old leaves, it
is preferable to use the B content of these tissues as an indication of the
status of sugar beet plants from the toxicity point of view.
It is of economic interest that sugar beets tolerate high B since
there are many areas where high boron occurs in soils or irrigation
waters. These areas occur primarily in the western parts ofthis country
(3,9, 10) where sugar beets should be given preference over crops with
a greater sensitivity to high B situations.
Summary
Sugar beet plants were grown for 6 weeks in 20-liter pots containing
nutrient solutions with B ranging in amount from adequate to
extremely toxic. The lowest B concentration in solution was 0.5 ppm
and the highest was 128 ppm.
No significant decrease in growth oftops or fibrous roots occurred
in plants growing in 0.5, 1,2,4, or 8 ppm B. The first drop in yield for
these plant parts came at 16 ppm and then continued to drop at a fairly
uniform rate at 32, 64, and 128 ppm. A 50% reduction in growth for
tops and fibrous roots came at 28 ppm, and for beet roots at 16 ppm B.
Only a trace of symptoms appeared at 8 ppm and showed as a
mosaic chlorosis and cupping of tne old leaves. 'These symptoms became
worse with time and were very severe at the highest B concentrations.
A final symptom apeared as a spotting at the tips and edges of the
old leaves that moved downward with time as a continuous mass of

288 JOURNAL OF THE A. S. S. B. T.
necrotic tissues toward the bases of the leaves. The roots appeared
healthy at all B levels and a decrease in yield was the only evidence of
toxicity, even at 128 ppm B.
The B content of the leaves increased with their physiological age.
Blades were higher in B than the corresponding petioles by a factor of
as much as twelve. The B content of the old blades of the plants where
the first drop in top yield occurred was above 600 ppm. At this point
the mature blades had 450 and the young blades 300 ppm. It was
suggested that the old blades could be used as diagnostic material in
determining the B status of the nutrient medium in the toxic range.
The B content of the roots was low and of the order of magnitude
found in the petioles.
The sugar beet plant was found to be tolerant of B relative to some
crop'; studied by other investigators.
Literature Cited
(I) BRANDENB URG , E. 1940. Ueber die Grundlagen del' Boranwendung in
der Landwirtschaft. Phytopath. Zeitschr. 12: 1-112.
(2) CHAPMAN, HOMER D. and PARKER F. PRATT. 1961. Methods of Analysis
for Soils, Plants and Waters. University of Califormia, Division of
Agricultural Sciences, Berkeley, Ca. 309 p.
(3) EATON, F. M. 1935. Boron in soil and irrigation water and its effects
on plants with particula r references to the San Joaquin Valley
of California. USDA Tech. Bul. 448.
(4) EATON, F. M. 1944. Deficiency, toxicity, and accumulation of boron in
plants. J. Agr. Res. 69:237-277.
(5) EL-SHEIKH, ADELM., A ULRICH, S. K. AWAD and A. E. MAWARDY. 1971.
Boron tolerance of squash, melon, cucumber and corn. J. Am . Soc.
Hort. Sci. 96: 536-537.
(6) GRINSTEAD, R. R. and SI GR ID SNIDER. 1967. Modification of the
method for 10" level boron determination. Analyst 92: 532-533.
(7) IlCGHES, J. D. 1959. A nOlt' on foliar diagnosis of boron deficiency in
beetroot. Queensland J. Agr. Sci. 16: 85-86.
(8) JOHNSO N, C. M. and A. ULRICH. 1959. Analytical methods for use in
plant analysis. Cal. Agr. Exp. Sta. Bu!. 766.
(9) KELLEY, W. P. and S. M. BROWN. 1928. Boron in the soils and irrigation
waters of southern California and its relation to citrus and wain ut
culture. Hilgardia 3: 445-458.
(10) REEVE , R. C., A. F. PILLSBURY and L. V. WILCOX. 1955. Reclamation
of a saline and high boron soil in the Coachella Valley of California.
Hilgardia 24:69-91.
(II) UNITED STATES SALINITY LABORATORY STAFF, 1954. Diagnosis
and improvement of saline and alkali soils. USDA Handbook 60,
U. S. Govt. Printing Office, Washington, D. C. 160 p.
(12) VLAMIS,JAMES and ALBERT ULRICH. 1971 . bOl'On nutrition in the growth
and sugar content of sugarbeets. J. Am. Soc. Sugar Beet Technol.
16: 428-439.