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symmetrical trees. In practice, orthotropic
cuttings would be obtained either by “ hedg
ing ” seedlings and transplants, which would
also tend to maintain juvenility (7) or by us
ing chemical pinching agents to force sprouts
from the main stem.
Correlations between most parameters were
relatively consistent in sign and magnitude
except for the relationship between visible
terminal bud activity and percentage of root
ing. In the 2 studies involving the parameters
of cutting length and type, which included
laterals and terminals, the correlation be
tween percentage of rooting and percentage
of visibly active terminal buds was 0.48 to
0.54. In these 2 studies, individual replica
tion values for percentage of rooting and bud-
break ranged from 0 to 100. In contrast, the
correla tion was - 0.03 in the experiment ex
amining genotypic variation, which utilized
only laterals. The discrepancy seemed to be
related to the propensity of laterals to exhibit
consistently high visible bud activity, re
gardless of percentage of rooting.
Litera ture Cited
1. Black, D. K. 1972. The influence of shoot
origin on the rootin g of Douglas-fir stem cut
tings. Proc. Intern. Plant. Prop. Soc. 22:14 2-
159.
2. Fadl, N. S. and H. T. Hartmann. 1967. Re
lationship betw een seasonal changes in en
dogen ous promote rs and inhibi tors in pear
buds and cutting bases and the rootin g of
pear hardwoo d cuttings. Proc. Amer. Soc.
Hort. Sci. 91:96 -112.
3. Hinesley, L. E. and F. A. Blazich. 1980.
Vegetative propaga tion o f Abie s fr as er i by
stem cuttings. HortScience 1 5:96-9 7.
4. Hinesley, L. E. and F. A. Blazich. 1981.
Influence of postse verance t reatments on the
rooting capacity of Fraser fir stem cuttings.
Can. J. For. Res. 11:3 16-323 .
5. Lave nder, D. P. and R. K. Hermann. 1970.
Regulation of the growth potential of Doug
las fir seedlings during dormancy. New Phy-
tol. 69 :67 5-694.
6. Lave nder , D. P., G. B. Sweet, J. B. Zaerr,
and R. K. Hermann. 1973. Spring shoot
growth in D ouglas-fir may be in itiated by
gibberellins exported from the roots. Science
182:838-839.
7. Libby, W. J. and J. V. Hood. 1976. Juv e
nility in hedged radiata pine. Acta Hort.
56:91-98.
8. Liu, T. S. 1971. A mon ograph o f the genus
Abies. Dept, o f Forestry, National Tiawan
University, Taipei, Taiwan.
9. Mille r, N. F., L. E. Hin esley, and F. A.
Blazich. 1982. Rooting of Fraser fir cuttings:
effects of post-severa nce chilling and pho
toperiod during rooting. Can. J. For. Res.
12:607-611.
10. Patton, R. F. and A. J. Riker. 1958. Root ing
cuttings of white p ine. For. Sci. 4 :116-12 7.
11. Roberts, A. N. and L. H. Fuchigami. 1973.
Seasonal changes in auxin effect on rooting
of Douglas -fir stem cuttings as relate d to bud
activit y. Physiol. Plant. 28 :21 5-2 21 .
12. Roberts, A. N., B. J. To masovic, and L. H.
Fuchigami. 1974. Intensity of bud dormancy
in Douglas-fir and its relation to scale re
moval and roo ting ability . Phy siol. Plant.
31:211-216.
13. Satoo, T., K. Negis, and K. Nakamura. 1953.
Relationsh ip betw een the rooting and age o f
trees from which cuttings are taken. An ex
perim ent using clonal materials. J. Japan.
For. Soc. 3 5: 69 -7 0.
14. Skene, K. G. M. 1975. Cytokinin produc
tion by roots as a factor in the control of
plant growth, p. 365-396. In: J. G. Torrey
and D. T. Clarkson (eds.). The development
and function of roots. Academic Press, N. Y.
15. Sorensen, F. C. and R. K. Campbell. 1980.
H or tS c ie nc e 17 (5): 829-8 31 . 1982.
Difficulties involved in making continu
ous, nondestructive root system evaluations
have resulted in the development of turfgrass,
forage, and pasture cultural systems based
on the responses of the grass shoot. Because
of this, the potential importance of root sys
tem characteristics and seasonal behavior in
such cultural systems has yet to be fully in
vestigated. Many cultural difficulties, in
cluding turfgrass establishment and unusual
pesticide phytoto xicity, could be manifesta
tions of a weakened grass plant resulting from
a poorly developed root system (9, 10, 11,
12).
Earlier rooting studies on perennial grasses
were conducted with cool season, C-3 spe
cies (3) using periodic evaluation methods
‘Receiv ed for publicatio n Feb. 16, 1982. Pub
lished as paper no. TA 14579, Journal Series, Texas
Agricultural Expt. Station, College St ation, TX
77843.
The cost of pu blishing this paper was defrayed
in part by the payment of page charges. Under
postal re gulations, this paper therefore must be
hereb y marked adv ertisemen t solely to indicate this
fact.
2Graduate Assistant-Research (now Assistant Pro
fessor, Crop Science Dept., North Carolina State
University , R aleig h, NC 27650), Professor, and
Research Scientist, respectively. The assistance of
L. D. Boyle, K. E. Bro wn, D. Chaffin, and D. S.
Schw epler during this investigation is gratefully
acknowledg ed.
Genetic variation in roo tabilit y of cuttings
from one-year-old weste rn hemlock seed
lings. U.S. For. Serv., Pac. Northwest For.
Range Expt. S ta., Res. Note PNW-352.
16. Thor, E. 1966. Re search with native Abies
in the southern Appalachians. Amer. Christ
mas Tree J. 12(4):2 9-3 3.
(13, 14, 15, 16). This investigation is the
first to utilize continuous (daily) root obser
vation procedures to study the seasonal be
havior of 2 major perennial warm season C-
4 grass species. This report covers the first
2 years o f a continuing investigation con
ducted in the Texas A&M University Turf
grass Rhizotron. The rhizotron consisted of
2 rows of 24 root observation boxes, each
having dimensions of 25 cm wide x 30 cm
long x 75 cm deep. Details pertaining to the
rhizotron construction and design were re
ported earlier (4, 5, 6, 7, 8).
‘Floratam’ St. Augustinegrass and ‘Tif-
green’ bermudagrass sods were transplanted
into the root observation boxes in August
1976. Phosphorus (P) was applied annually
to the turfs as superphosphate at a rate of 148
kg of actual P per hectare. The initial appli
cation of phosphate (August 1976) was in
corporated into the upper 1 0 cm of the soil.
All turfs received nitrogen (as K N0 3 and
(NH4)2S 04) and potassium (as KN 03) at a
rate of 49 kg of actual nutrient (N or K) per
ha- growing month. The turf was mowed
weekly at a 5-cm cutting height for ‘Flora-
tarn’ and a 2 .5-cm cutting height for ‘Tif-
green’. Irrigation was applied as needed to
prevent wilting. Treatments were replicated
4 times. Soil temperatures were recorded
continuously at 10- and 30-cm depths with a
2-pen Foxboro temperature recorder begin
ning in October 1977, while previous soil
temperatures were periodically monitored us-
Key Events in the Seasonal Root
Growth of Bermudagrass and St.
Augustinegrass1
J. M. DiPaola, J. B. Beard, and H. Br aw and 2
Texas A& M University Soil and Crop Science Department, College
Station, TX 77843
Add itional index words, turf, lawngrass, Poaceae, Cynodon spp., Stenotaphrum
secundatum
Abstract. Root growth of St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze]
and berm udagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Davy] (C-4 plants),
show distinct seasonal patterns different from those of the cool-season perennial grasses
(C-3 plants). Root growth continued after winter shoot dormancy occurred, and at soil
temperatures below 10°C. Severe browning of the entir e root system was observed just
after spring shoot greenup followed by a delay of about 3 weeks in new root initiation
and replacement, even though significant shoot development was occurring prior to
this period of root initiation.
Hor t Sc i e n c e , V o l . 1 7(5), Octo b e r 1982. 8 29
Fig. 1. St. Augustinegrass mean root extension rate (cm/day) and the minimum soil te mperature (°C)
at a 10-cm depth from Oct. 23, 1977, through Jan. 27, 1978. (A) Chilling injury was first observed
on Nov. 21, 1977. (B) No f urther shoot growth occurred after Dec. 3, 1977. (C) The first 5 frosts
occurred at the end of December.
ing copper-constantan thermocouples. Root
extension lengths were recorded daily by
tracing root growth on clear acetate sheets
which were pressed against the glass plate of
the root observation boxes.
Sum m er rooting responses. Individual
root extension rate of both species averaged
2 . 8 cm /day during the warm summ er months.
Daily root extension rates ranged from 0 to
10 cm/day for individual roots. Daytime cloud
cover resulted in reduced nocturnal root ex
tension rates in a previous greenhouse in
ve st ig atio n (4). The av er ag e da ily r oot
extension rate for these 2 warm season spe
cies was 5 times greater than the rate reported
by Beard (1,2 ) for creeping bentgrass (Agrostis
palustris Huds.) and Weaver (15) et al. for
winter wheat (Triticum aestivum L.), both
cool season species.
New root initiation, root maturation, and
death of older roots continued through the
summer months. Rooting depths for both
species were in excess of 70 cm; however,
the majority of the root system was located
in the upper 30 cm o f the soil (Table 1).
‘Floratam’ roots were substantially fewer in
number per unit area of sod and larger in
diameter than those of ‘Tifgreen ’. St. Au-
<
l/>
V
CO
Percent
March April
Fig. 2. Key events in the shoot and root development of ‘Tifgre en’ bermudagrass and ‘Flora tam ’ St.
Augustineg rass and soil te mpera ture during spring of 1978. (A) Appearance of the first new leaves,
(B) root brow ning, (C) new root initiation, and (D) the first root reaches a 30-cm depth.
Table 1. St. Augustinegrass and bermudagrass
root system profiles as sampled in Novem ber
1976, about 3 months after establishment.
Soil layer
depth
(cm)
St. Augus tine
grass Berm udagras s
Root dry
wt
(mg)
% of
total
Root dry
wt
(mg)
% of
total
0- 10 256 ez 52 387 c 62
10-20 123 cd 25 139 b 22
20 -3 0 77 be 16 69 a 11
30 -40 35 ab 7 29 a 5
zMeans s eparation within columns by Du ncan’s
multiple range test, 5% level.
gustinegrass had up to 28 actively growing
roots visible through the grass facing of the
root observation boxes, while the bermuda
grass turfs had up to 60 actively growing
roots visible per plate.
Fall rooting responses. Root extension
rates of ‘Floratam’ gradually decreased as fall
soil te mperatures declined (Fig. 1). The root
extension rate averaged 1.3 to 1.5 cm/day
during the last 2 weeks in October 1976 and
1977. Respective soil temperature means at
a 1 0 cm depth for these 2-week periods were
15.5 and 20.1°C.
Chilling symptoms (initially appearing as
a purple leaf coloring) were observed on the
‘Floratam’ turfs on Oct. 26, 1976, and Nov.
21, 1977. The mean soil temperatures at a
10-cm depth were 15.3 and 17.2°C, respec
tively. ‘Tifgreen’ developed chilling injury
symptoms about 3 days later than ‘Floratam’
in 1977. ‘Tifgreen ’ shoot growth essentially
ceased after Oct. 1, 1976, and Dec. 3, 1977.
Root growth continued for almost 30 days
after shoot growth ceased in 1977.
Winter root responses. During the pe
riod between the last day of measurable root
growth in early winter and the initiation of
new shoot growth the following spring, the
roots of both species remained a white to
light-tan color. As such, they were assumed
to be alive and capable of functioning. No
root growth occurred after Jan. 21, 1978,
until the occurrence of spring new root ini
tiation. The mean soil temperature at a 10-
cm depth for the remaining portion of Jan
uary, February, and March 1-21 were 1.9,
5.4, and 11.4°C, respectively. New root ini
tiation was not observed during the winters
of 1976-1977 and 1977-197 8.
Spring root responses. The first new
leaves initiated from ‘Tifgreen’ were ob
served on March 21, 1978, while those of
‘Floratam’ were visible on March 22, 1978
(Fig. 2). On March 26, the roots of both
species underwent a rapid color change from
white-light tan to brown. A similar color
change of the roots was also observed during
leaf-greenup in early spring for 1977 and 1979.
After March 26, 1978, both the ‘Floratam’
and ‘Tifg re en ’ turfs produced sig nificant
amounts of new green leaves without any
outward signs of new root initiation. ‘Tif
green’ shoots and roots developed earlier in
the spring than those of ‘Floratam’ (Fig. 2).
New spring roots of ‘Tifgre en’ did not reach
830 Ho r t Sc i e n c e , V o l . 1 7(5), Oct o b e r 1982.
a depth of 30 cm until mid-April of 1978,
while ‘Floratam’ roots did not achieve this
depth until late April.
Three previously unknown seasonal root
growth characteristics of 2 warm season (C-
4) perennial grasses have been observed dur
ing this investigation. First, fall root growth
occurred at surprisingly low soil tempera
tures. Although the amount of growth was
small, its occurrence at soil temperatures be
low 10°C for these warm-season, perennial
grass species was not expected, nor previ
ously reported in the literature. Second, root
growth continued in the fall after shoot growth
ceased and conditional shoot dormancy had
occurred. There appear to be distinct shoot
and root dormancy phases during the fa ll -
early winter months, rath er than a general
plant dormancy. This finding is in direct con
trast to a report by Weaver et al. (15) with
a C-3 annual grass, ‘Kanred’ red winter wheat.
Root growth of ‘Kanred’ winter wheat was
observed to cease sim ultaneously with that
of the above groun d parts. T hird, severe
browning of the entire observable root sys
tems of both grasses occurred just after spring
shoot greenup was observed. ‘Tifg reen’ ex
hibited a 1-day delay, while ‘Floratam’ had
a 2-week delay before new root initiation
occurred following the spring root senes
cence phenomenon. This rooting delay was
actually longer from a practical standpoint,
since it took about 20 and 15 days for any
newly initiated ‘Tifgreen’ and ‘Floratam’ root,
respectively, to reach a soil depth of 30 cm.
Thus, the effective spring rooting delay for
both grasses in 1978 was about 3 weeks.
It can be speculated that the restricted spring
root growth is at least partially the result of
internal plant factors such as carbohydrate
availability to the root and hormonal con
centrations. Evidence for such speculation is
seen in the observation that root growth con
tinued in the fall but not during the early
spring, even though soil temperatures at those
times were comparable.
The limited root system during this late
winte r-early spring period could increase the
proneness to injury from low-temperature
stress, desiccating winds, traffic, diseases,
and ins ec t p ests. Period ic reports from
throughout the southern United States have
noted such problems during this period (9,
10, 11, 12). Furthermore, pesticide appli
cations at normal rates, which result in no
observable injury when applied at other times
during the growing season, have caused p hy
totoxicity problems if applied during this spring
root loss period (9, 10, 11). The inability of
grasses to root adequately during this spring
greenup period is probably a major contrib
uting factor to these winterkill, pesticide, and
establishment problems.
Literature Cited
1. Beard, J. B. and W. H. Daniel. 1965. Effect
of tem perature and cuttin g height on the
growth of cr eeping bentgrass {Agrostis pal-
ustris Huds.) roots. Agron. J. 57:2 49-25 0.
2. B eard, J. B. 1966. Relationship of creeping
bentgrass (Agrostis pa lustris Huds.) root
growth to en vironm ental factors in the field.
Agron. J. 58:3 37 -339.
3. Brown, R. H. 1978. A difference in N use
efficie ncy in C-3 and C-4 plants and its im
plication in adaptation and evolution. Crop
Sci. 18 :93-98.
4. DiPa ola, J. M. 1977. Desic cation resistance
and root growth rate of St. Augustinegrass
{Stenota phrum secun datum [W alt.] Kuntze
‘Floratam’) as influenced by potassi um. MS
Thesis, Texas A&M Univ., College Station.
5. DiPaola, J. M. and J. B. Beard. 1976. De
velopm ent of a tu rfgrass rhizotron at Texas
A&M. Proc. 31st Annu. Texas Turfgrass
Conf. 31:1 14-11 7.
6. DiPaola, J. M. and J. B. Beard. 1977. In
fluence of potassium on root growth o f newly
planted sod. Soil & Crop Sci. Dept. Res.
Rpt. Texas A&M Univ. 77-5 4:1 3-18.
7. DiPaola, J. M. and J. B. Beard. 1977. Root
and .shoot response of St. Augus tinegrass to
water stress as influenced by potassium. Proc.
32nd Annu. Texas Turfgrass Conf. 32:1 29-
132.
8. D iPaola, J. M. and J. B. Beard. 1978. Sea
sonal rooting ch aracteristics of bermudagrass
and St. A ugusti negrass. Texas Agr. Expt.
Sta. PR 3485 :5 -11 .
9. Johnson, B. J. 1976. Bermuda grass toler
ance to conse cutive butraline and oxadiazon
treatm ents. Weed Sci. 24:302 -305.
10. Johnson, B. J. 1978. Response of Zoysia
(Zoysia sp p.) and bermudagrass (Cynodon
dactylori) cultivars to herbic ide treatm ents.
Weed Sci. 26 :49 3-497 .
11. John son, B. J. 1980. Root growth of sou th
ern turf cultivars as affecte d by herbicides.
Weed Sci. 28:52 6-528 .
12. Schroder, V. N. and O. C. Ruelke. 1968.
Nutritional studies of root and shoot devel
opmen t o f yellowed bahiag rass. Soil & Crop
Sci. Soc. Fla. Proc. 28 :3 5-4 2.
13. Spra gue, H. B. 1933. Root development of
perennial grasses and its relation to soil con
ditions. Soil Sci. 36:1 89 -209.
14. Stuckey, I. H. 1941. Seasonal growth o f grass
roots. Amer. J. Bot. 2 8:4 86-49 1.
15. Weaver, J. E ., J. Kramer, and M. Reed.
1924. Development of root and shoot of win
ter wheat under field environm ent. Ecology
5:26-50.
16. Weaver, J. E. and E. Zink . 1946. Length of
life o f roots of ten species of perennial range
and pasture grasses. Plant Physiol. 21 :20 1-
217.
SCHEDULE OF FUTURE MEETINGS OF THE
AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE
Name & Date of Meeting Location Comments
80th Annual ASHS Meeting McAllen, Texas
October 16 -2 2,1983 International Civic
& Convention Center
Accommodations will be at several hotels and motels near the
convention center. Tours of diverse horticultural industry in the Rio
Grande Valley area will be featured.
81 st Annual ASHS Meeting University of British
August 5- 11,19 8 4 Columbia, Vancouver
A jo int meeting with the Canadian Society for Horticultural Science.
Tours and sightseeing will be planned.
82nd Annual ASHS Meeting
Ju ly 2 8—Au g. 2 , 1985
Virginia Polytechnic Campus facilities will be used for program sessions and housing.
In stitut e & S U, B lac ksb urg H or ticu ltu ra l t our s w ill b e pl an ned .
83rd Annual ASHS Meeting University of California
August 1 1-2 0, 1986 Davis Campus
Will be an integral part of the XXIInd International Hort. Congress,
hosted by ASHS and AH S. Accommodations will be on and off-
campus in the Davis/Sacram ento area. Tours and sightseeing will be
featured.
84th Annual ASHS Meeting Orlando, Florida
No vem be r6-14, 1987 Hyatt Orlando Hotel
The ASHS Tropical Region plans to meet with the parent Society.
Tours and sightseeing will be featured. Tourist attractions abound!
Ho r t Sc i e n c e , V o l . 17(5), Oct o b e r 1982. 831
