cerned with nitrogen (N) fertilization regarding drought re sistance in rugosa rose . Neither N deficiency or excess adversely affected the ability of leaves to ...
This Journal of Environmental Horticulture article is reproduced with the consent of the Horticultural Research Institute (HRI – www.hriresearch.org), which was established in 1962 as the research and development affiliate of the American Nursery & Landscape Association (ANLA – http://www.anla.org). HRI’s Mission: To direct, fund, promote and communicate horticultural research, which increases the quality and value of ornamental plants, improves the productivity and profitability of the nursery and landscape industry, and protects and enhances the environment.
The use of any trade name in this article does not imply an endorsement of the equipment, product or process named, nor any criticism of any similar products that are not mentioned.
Copyright, All Rights Reserved
Turgor Maintenance in Rosa rugosa Grown at Three Levels
of Nitrogen and SUbjected to Drouqht' R.M. Auge, A.J.W. Stodola and D.M. Gealy! Department of Ornamental Horticulture and Landscape Design
University of Tennessee, Knoxville, TN 37901-1071
r-------------------
Abstract - - - - - - - - - - - - - - - - - - - - .
The influence o~ ~ fertilization on t~rgor maintenance was determined in leaves from well-watered and droughted Rosa rugosa L. Plants were fertilized for 60 days WIth ~ .complete fertilizer with N at levels of 0, 200 or 500 ppm and then subjected to several drought cycl~s for 22 ~ays. Plants receivmg no N were stunted and chlorotic, but had the greatest full saturation turgor pressure and symplastIc osmolality, and the l.owest full sat.uration osmotic potential, after drought. These plants also maintained higher turgor across a range of. leaf water potentIa~s and relat~ve water contents. Leaf water content at full turgor and relative water content at the turgor loss pomt were also lower In plants WIthout N. N treatments of 200 and 500 ppm had similar water relations under both well-watered and drought conditions. '
Index words: nutrient deficiency, nutrient excess, rose, water stress
Significance to the Nursery Industry Turgor is an essential prerequisite for plant growth. When turgor falls below a certain minimum value, growth stops. To protect against this during drought conditions, plants have developed several mechanisms for turgor maintenance. Results herein suggest that growers need not be overly con cerned with nitrogen (N) fertilization regarding drought re sistance in rugosa rose . Neither N deficiency or excess adversely affected the ability of leaves to maintain turgor during drought. In fact, turgor of deficient plants was ap proximately twice that of adequate and high N treatments. This, combined with A) the fact that high N plants were slightly smaller than adequate N plants, B) the general ten dency of high N plants to be less stress resilient, and C) the added costs of high N, may act as a reminder that supra optimal N rates are unnecessary and in most instances un desirable.
Introduction Drought stress, which probably accounts for more world wide crop damage than all other causes combined (7), can also be a severe problem in non-irrigated nurseries and out plant sites. Even the usual episodes of water deficit during average growing seasons often constitute a serious threat to survival of new plantings and vigor of established plantings. Successful transplanting and cultural practices require def inite knowledge of the physiology of plants under water limiting conditions. Plants have evolved several morphological and physio logical adaptations which enable them to tolerate or avoid drought and maintain turgor. Drought diminishes or halts growth, usually directly through reductions in turgor po tential ( a:
50
C)
~ 0
I
8 I
en
40 30 20
10
70
0
WELL WATERED
~
DFO.GIT
®
I
«
~~
W
z
~o u~ a: a:
60 50
0
40
w::>
1-1
«« ~
en.
30
-J
LL-J «::> w LL
20
-J
o
200
500
NITROGEN FERTILIZATION (ppm)
Fig. 2.
110
Total shoot dry weight (A), leaf water content at full hydration (B) and relative water content at the turgor loss point (C) of well-watered and droughted plants of Rosa rugosa receiving 0, 200 or 500 ppm N. Each value represents the mean of six observations; vertical lines represent + 1 SEe
.007
.01
.01
.0001
.007
.01
NS NS NS
NS NS NS
NS NS NS
NS
NS NS NS
NS NS NS
.03
NS
given no nitrogen but caused no change in plants of either N-fed treatment. Turgor was much greater in droughted plants receiving no N than in any other treatment throughout almost the entire range of «/J and RWC between full turgor and zero turgor t.(Fig. 4). Plants supplied with 200 and 500 ppm N exhibited similar «/Jp/«/J and «/J-/RWC relationships after both well-watered and drought conditions (Figs. 4B and 40). Drought resulted in turgor enhancement only in plants given no N, and the enhancement ranged from 0.3 to 0.7 MPa (Figs. 4A and 4C). Turgor decreases upon leaf dehydration were imme diate in all treatments except droughted plants without N, which sustained very little «/Jp loss above 93% RWC (Figs. 4C and 40). Both tissue N (9) and drought (16) affect the size and composition of solute pools within the various compart ments in plant protoplasm and hence can directly influence «/J components. Simultaneous investigation of varied N fer tilization and drought in Rosa rugosa revealed a surprising fact: deficient plants exhibited greater «/Jp than plants given adequate or supra-optimal levels of N. Generally, our ex pectations are the reverse; deficient plants often perform more poorly than those that are optimally nourished, under otherwise nonstressful conditions as well as when con fronted with additional environmental hardships. However, when viewed in terms of either decreasing leaf «/J or RWC, turgor of droughted, N deficient plants was roughly twice that of plants receiving higher N levels. N deficiency has previously been associated with turgor maintenance in leaves to lower «/J (12). Although N levels low enough to retard growth certainly cannot be recommended as an approach for enhancing drought resistance, it is noteworthy that N fertilized plants may not outperform deficient plants during stress but may actually be inferior in terms of turgor main tenance. The first objective of our study was to determine if N deficiency reduces drought resistance. The answer must be no. Although growth was severely retarded by N defi ciency, deficient plants maintained greater turgor during drought. The second objective was to investigate the possible effect of supra-optimal N fertilization on «/Jp maintenance with drought. Excess or disproportionate N relative to other ele ments may provide additional growth but may also result in tissues with lowered resistance to stress (19). This did not occur in the study; plants fertilized with 500 ppm N on a continuous liquid feed basis did not show increased growth or altered water relations after drought, compared to fertil ization with 200 ppm. Tissue N levels were, however, only J. Environ. Hort. 8(3):108-112. September 1990
200
200
500
NITROGEN FERTILIZATION (ppm)
500
NITROGEN FERTILIZATION (ppm)
Fig. 3. Water potential components (A and B) and symplastic osmolality (C and D) of leaves of well-watered and droughted plants of Rosa rugosa receiving 0, 200 or 500 ppm N. Measurements were made by the pressure-volume technique . Each value represents the mean of six observations; vertical lines represent + 1 SE.
2.0
o
Own N, DAOUGHT
o
• oppm N, WEll WATERED
~ ~
0
,200 ppm N. DROUGHT
200 ppm N, WELL WATERE'~
1.5
::>
'" w '" a: a.
o 1.0
...
o
t
0.5
~
Ii. 200 ppmN. DROUGHT •
~
1.5
200 ppm N, WELL WATERED
- -
t!
•• /
~ /'~ 6~/. /
#
6............
tJ.
200 ppm N. DROUGHT
..
200 ppm N, WEll WATERED
o
500 ppm N. DROUGHT
o
500 ppmN. DROUGHT
•
500 ppm N. WEll WATERED --- - - - - -
•
500 ppm N, WEll WATERED
;;?'-/
~:
_.
lB'"a:
1.0
a.
a:
o
oa:
...
::>
0.5
-1 .0
-0 . 5
WATER POTENTIAL (MPa)
Fig. 4. Relationship between turgor pressure and water potential (A and B) and turgor pressure and relative water content (C and D) in well watered and droughted plants of Rosa rugosa receiving 0,200 or 500 ppm N. Measurements were made by the pressure-volume technique. Curves were fitted with RWC as the independent variable; each data point is the mean of three observations. Bars represent 2 x the pooled standard error of the means.
J. Environ. Hort. 8(3):108-112. September 1990
III
slightly higher in plants supplied with the higher N rate and then only following drought. There is evidence that N0 3 is absorbed independently of the N0 3- concentration in the root environment (4), and its accumulation depends on tissue carbohydrate concentrations (18). If neither N nor C were limiting growth, then, it may not be surprising that plants of each N-fed treatment developed similar total N levels and carbohydrate pools under similar irradiance. The N requirements of the many plant species grown as potted ornamentals are extremely varied, and the ideal level of N for any particular species depends on the many environ mental factors specific to certain sites (19). Leaf N content of plants of both 200 and 500 ppm N treatments were within the range generally considered optimal for cultivated Rosa: from 3 to 5% tissue N on a dry weight basis (20). The higher symplastic osmolalities in N deficient plants were likely due to growth inhibition. Actively growing cells normally exhibit lower solute concentrations than cells in which division and enlargement has ceased (9). Presumably, solutes accumulated as demand for structural components subsided. Plants showed the lowest f/J7T (highest solute con centrations) when both N and water deficiency acted to retard growth. Plant N status has been reported to affect a number of water relations characteristics. Stomatal sensitivity changes in several species as a result of N deficiency (3, 10, 11, 13), and increased water use efficiency stemming from high N levels has been demonstrated in tall fescue (Festuea arun dinacea Schreb.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) (3, 5). Reports of N effects on turgor and osmotic adjustment are conflicting. Drought-induced ad justment in these f/J components was observed to increase with both ample N fertilization, in com (Zea mays L.), and deficient N fertilization, in cotton tGossypium hirsutum L.) (2, 12). Furthermore, f/J7T may remain unaffected by N sup ply, as in sorghum (Sorghum bicolor L.) (2). N0 3- was reported to play a role in osmotic adjustment of ryegrass by compensating for shortages of other solutes (18). There is no reason to suspect that photoassimilate or other nutrients were limiting in our study, and Rosa rugosa did not appear to rely upon osmotically active forms of N for solute reg ulation during drought conditions.
Literature Cited 1. Auge, R.M. and A.J.W. Stodola. 1989. Analysis of water potential isotherms in two ornamental shade tree species entering winter dormancy. J. Amer. Soc. Hort. Sci. 114:666-673. 2. Bataglia, O.C., J.A. Quaggio, O. Brunini and D.M. Ciarelli. 1985.
112
Effect of nitrogen fertilization on osmotic adjustment in maize and sorghum. Pesq. agropec. bras., Brasilia 20:659-665. 3. Brix, H. and A.K. Mitchell. 1986. Thinning and nitrogen fertilization effects on soil and tree water stress in a Douglas-fir stand. Can. J. For. Res. 16:1334-1338. 4. Clement, C.R., M.J. Hopper and L.H.P. Jones. 1979. The uptake of nitrate by Lolium perenne from flowing nutrient solution. J. Expt. Bot. 29:453-464. 5. Ghashghaie, J. and B. Saugier. 1989. Effects of nitrogen deficiency on leaf photosynthetic response of tall fescue to water deficit. Plant Cell Environ. 12:261-271. 6. Hewitt, E.J. andC.V. Cutting. 1979. Nitrogen assimilation of plants. Academic Press, New York, p. xiv. 7. McWilliam, J.R. 1986. The national and international importance of drought and salinity effects on agricultural production. Austral. J. Plant Physiol. 13:1-13. 8. Morgan, J.M. 1984. Osmoregulation and water stress in higher plants. Annu. Rev. Plant. Physiol. 35:299-319. 9. Mott, R.L. and F.C. Steward. 1972. Solute accumulation in plant cells. V. An aspect of nutrition and development. Ann. Bot. 36:915-937. 10. Nagarajah, S. 1981. The effect of nitrogen on plant water relations in tea (Camelia sinensis). Physiol. Plant. 51:304-308. 11. Radin, J. W. and R. C. Ackerson. 1981 . Water relations of Cotton plants under nitrogen deficiency. III. Stomatal conductance, photosyn thesis, and abscisic acid accumulation during drought. Plant Physiol. 67:115 119. 12. Radin, J. W. and L. L. Parker. 1979 . Water relations of cotton plants under nitrogen deficiency. I. Dependence upon leaf structure. Plant Phys iol. 64:495-498. 13. Radin, J.W. and L.L. Parker. 1979. Water relations of cotton plants under nitrogen deficiency. II. Environmental interactions on stomata. Plant Physiol. 64:499-501. 14. Steel, R.G.D. and J.H. Torrie. 1980. Principles and procedures of statistics. 2nd ed. McGraw-Hill, New York. 15. Thomas, R.L., R.W. Sheard and J.R. Moyer. 1967. Comparison of conventional and automated procedures for nitrogen, phosphorus, and potassium analysis of plant material using a single digestion. Agron. J. 59:240-243. 16. Turner, N.C. and M.M. Jones. 1980. Turgor maintenance by os motic adjustment: A review and evaluation, p. 87-103. In: N.C. Turner and P.J. Kramer (eds.). Adaptation of plants to water and high temperature stress. John Wiley & Sons, New York. 17. Tyree, M.T. and P.G. Jarvis. 1982. Water in tissues and cells, p. 35-77. In: O.L. Lange, P.S. Nobel, C.B. Osmond and H. Ziegler (eds.). Encyclopedia of plant physiology 12B: Physiological plant ecology II. Springer-Verlag, New York. 18. Veen, B.W. and A. Kleinendorst. 1986. The role of nitrate in osmoregulation of Italian ryegrass. Plant Soil 91 :433-436. 19. Whitcomb, C.E. 1984. Plant production in containers. Lacebark Publications, Stillwater, OK, p. 238-239. 20. White, J.W. 1987. Fertilization, p. 102. In: R.W. Langhans (ed.). Roses. Roses Incorp., Haslett, Mich.
J. Environ. Hort. 8(3): 108-112. September 1990
