Plant management of greenhouse roses. Formation of renewal canes

Scien~a Horticulturae, 15 (1981) 67--75 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

67

PLANT MANAGEMENT OF GREENHOUSE ROSES. FORMATION OF RENEWAL CANES

N. ZIESLIN 1 and Y. MOR 2 ~Department of Ornamental Horticulture, The Hebrew University of Jerusalem, Rehovot (Israel) 2Department of Floriculture, Ministry of Agriculture (Israel)

(Accepted for publication 14 November 1980)

ABSTRACT Zieslin, N. and Mor, Y., 1981. Plant management of greenhouse roses. Formation of renewal canes. Scientia Hortic., 15: 67--75. Renewal shoot ("bottom break") formation in rose plants was affected by the temperature and relative humid!ty in the greenhouse. The number of shoots and the rate of their renewal were significantly higher in plants grown in a greenhouse cooled by evaporative coolers then in an uncooled greenhouse. A decrease in renewal shoot formation occurred which reduced light intensity above the stem base. This phenomenon was also observed in defoliated plants.

INTRODUCTION T h e f o r m a t i o n o f v i g o r o u s s t r u c t u r a l s h o o t s f r o m t h e basal p a r t s o f r o s e plants, k n o w n as " b o t t o m b r e a k s " , p l a y s an i m p o r t a n t role in t h e r o s e g r o w i n g T h e s e s h o o t s are i m p o r t a n t in t h e d e v e l o p m e n t o f y o u n g plants a f t e r p l a n t i n g , a n d e n s u r e a l o n g e r life s p a n f o r t h e rose p l a n t ( B y r n e a n d K o h l , 1 9 7 2 ; P l a n t a n d Zieslin, 1 9 7 4 ; Zieslin e t al., 1 9 7 6 ) a n d are also an i m p o r t a n t s o u r c e o f f l o w e r p r o d u c t i o n (Zieslin et al., 1 9 7 3 ) . A m o n g m a n y e n v i r o n m e n t a l , c h e m i c a l a n d o t h e r f a c t o r s , lateral b u d rem o v a l is also u s e d t o s t i m u l a t e t h e p r o d u c t i o n o f r e n e w a l s h o o t s ( " b o t t o m b r e a k s " ) ( K o h l a n d S m i t h , 1 9 6 9 ; Zieslin et al., 1 9 7 6 ) . T h e i n v o l v e m e n t o f e n v i r o n m e n t a l f a c t o r s such as c o o l i n g a n d light in t h e f o r m a t i o n o f r e n e w a l s h o o t s s t i m u l a t e d b y d e - s h o o t i n g was t h e s u b j e c t o f this s t u d y . GENERAL MATERIALS AND METHODS T h e e x p e r i m e n t s w e r e carried o u t at t h e e x p e r i m e n t a l g r e e n h o u s e o f t h e D e p a r t m e n t o f O r n a m e n t a l H o r t i c u l t u r e at R e h o v o t , Israel, e x c e p t f o r Exp e r i m e n t 2 w h i c h was p e r f o r m e d in t h e g r e e n h o u s e o f t h e D e p a r t m e n t o f E n v i r o n m e n t a l H o r t i c u l t u r e , U n i v e r s i t y o f California, Davis, U.S.A. T h e d a y

0304-4238/81/0000--0000/$02.50 © 1981 Elsevier Scientific Publishing Company

68 and night temperature regime was maintained at 28 and 18 ° C, respectively. The cooling-experiments were performed in a "Pad and F a n " cooled greenhouse which had a m a x i m u m day temperature of 26 ° C, a night temperature of 18 ° C, and relative h u m i d i t y (RH) of 70--80% during the day hours. The details of particular experiments will be described with the results. EXPERIMENTAL PROCEDURES AND RESULTS 1. - - The effect of de-shooting on the formation of renewal shoots in rose plants growing in different environmental conditions was examined. Two hundred 6-year-old plants, cultivar 'Baccara', grown in 10-1 containers in an uncooled greenhouse, were separated into 2 groups. One group of 75 plants were transferred to the "Pad and F a n " co61ed greenhouse. The second group of 125 plants continued growing in a greenhouse without an evaporative cooling system. In this uncontrolled greenhouse, the day temperature reached 36°C on very bright days and the RH fluctuated from 30 to 60%. On 15 February, 50 plants in the cooled and 100 plants in the uncooled greenhouse were pinched and continuously de-shooted thereafter. T w e n t y five plants in each greenhouse remained untreated for free growth and served as control plants. The de-shooting was continued for 6 weeks until 4 April. On this date, the de-shooting was discontinued and after the detection of the renewal shoots in these plants, 75 plants were transferred to the "Pad and F a n " greenhouse, which left 25 plants in the uncooled house. An additional count of the renewal shoots was made on 1 May, about 1 m o n t h after the plant transfer. Only the vigorous shoots which developed no higher than 5 cm above the graft union were considered to be " b o t t o m breaks". T h e results, summarized in Table I, show t h a t in the uncooled greenhouse only a few renewal shoots had been formed in both de-shooted and non-de-shooted plants. Not more than 6--8% of the plants show renewal, with an average of 1 shoot per plant. On the other hand, with cooling 24% of plants without de-shooting and 74% of the de-shooted plants had developed renewal shoots, amounting to 2.3 renewal shoots per plant, The transfer of 75 de-shooted plants from an uncooled house to a cooled one caused 57% of those plants to produce new shoots ( b o t t o m breaks) after 4 weeks, with 1.6 shootS per plant. During this period, only 28% of the plants left in the uncooled greenhouse showed renew M (Table I).

Experiment

2. - - The positive effect of light on rejuvenation of rose plants, which is well k n o w n in horticultural pratice, was studied. Twenty-eight rose plants, cultivar 'Forever Yours', were grown in 20-1 containers in a greenhouse with evaporative coolers. After pruning to 60 cm above the graft union on 17 May, the plants were divided into groups of 4 according to the following treatments: (1) The plants were defoliated and all sprouting buds ( ~ 1 cm) were continuously removed; (2) As in (1), but the graft union was covered with aluminum foil immediately after pruning; (3) The sprouting buds were

Experiment

69

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70 l e f t in free g r o w t h u n t i l t h e f l o w e r b u d s a p p e a r e d . A f t e r p i n c h i n g t h e f l o w e r b u d s (1 J u l y ) , all t h e laterals w h i c h a p p e a r e d were d e - s h o o t e d ; (4) As in (3), a n d t h e g r a f t u n i o n was c o v e r e d w i t h a l u m i n u m foil i m m e d i a t e l y a f t e r p r u n i n g ; (5) As in (3), b u t t h e g r a f t u n i o n was c o v e r e d w i t h a l u m i n u m foil a t t h e t i m e o f f l o w e r b u d r e m o v a l o n 1 J u l y ; (6) C o n t r o l - - 8 p l a n t s w e r e l e f t in free g r o w t h a f t e r p r u n i n g w i t h o u t d e - s h o o t i n g or c o v e r i n g o f t h e g r a f t union. O n 1 J u l y , 6 w e e k s a f t e r p r u n i n g , t h e a l u m i n u m foil c o v e r was r e m o v e d , e x c e p t in T r e a t m e n t 5 w h e r e t h e c o v e r h a d b e e n r e m o v e d on 5 S e p t e m b e r a n d t h e n u m b e r o f t h e r e n e w a l s h o o t s h a d b e e n d e t e r m i n e d . T h e results o f t h e e x p e r i m e n t ( T a b l e I I ) s h o w t h a t e x c l u s i o n o f light f r o m t h e g r a f t u n i o n tissue a l m o s t c o m p l e t e l y p r e v e n t e d t h e a p p e a r a n c e o f r e n e w a l s h o o t s , e i t h e r in t h e p r e s e n c e or t h e a b s e n c e o f leaves. TABLE II Effect of de-shooting and darkening of the graft union on the development of the basal renewal shoots in roses 'Forever Yours'. The plants were pruned on 17 May. Four plants per treatment Treatments

Pruning, defoliation, continuous de-shooting Pruning, no defoliation, free growth, flower bud pinching on July followed by de-shooting As above, graft union was covered on 1 July Control, pruning, no pinching, no de-shooting ( 8 plants)

Renewal shoots per treatment Graft union uncovered

Graft union covered

6

1

5 41 2

o 02

1 Four first breaks were removed on 1 July before covering. 2The second count on 5 September.

Expertment 3. --~'Forever Y o u r s ' is n o t a b l y a d i f f i c u l t cultivar t o r e n e w w i t h b o t t o m b r e a k s ( H a l e v y a n d K o h l , 1 9 7 1 ) . Cultivars w i t h m o r e b u s h y f o r m s u c h as ' M e r c e d e s ' d e v e l o p r e n e w a l s h o o t s m o r e readily. T h e r e f o r e , t h e eff e c t o f light p r e v e n t i o n f r o m t h e g r a f t u n i o n was r e p e a t e d l y t e s t e d o n t h e "bushy" 'Mercedes'. F o r t y - t w o u n i f o r m p l a n t s w e r e s e l e c t e d a n d p r u n e d o n 5 D e c e m b e r , 80 c m a b o v e t h e soft. All b u t o n e s t r o n g c a n e w e r e r e m o v e d . T h e p l a n t s w e r e divided i n t o 3 groups, 14 p l a n t s each, a c c o r d i n g t o t h e f o l l o w i n g t r e a t m e n t s : (1) C o n t r o l - - n o g r a f t u n i o n s w e r e c o v e r e d ; (2) T h e u n i o n s w e r e c o v e r e d w i t h a l u m i n u m foil o n t h e p r u n i n g - d a y ; (3) As in (2), b u t a h o l e facing u p w a r d , 6 - - 8 m m in d i a m e t e r , was m a d e in t h e a l u m i n u m foil cover. T h e r e n e w a l s h o o t s w e r e c o u n t e d 4 w e e k s a f t e r p r u n i n g ( T a b l e III). Excluding light f r o m t h e g r a f t u n i o n f o r o n l y 4 w e e k s was s u f f i c i e n t t o decrease r e n e w a l s h o o t f o r m a t i o n b y ca. 40% c o m p a r e d t o t h e u n c o v e r e d c o n t r o l

71 TABLE III The influence of light prevention from the graft u n i o n on the formation of basal renewal shoots of roses 'Mercedes'. Fourteen plants per treatment Treatments

Number of plants renewed (out of 14)

Number of renewal shoots

Control - - no covering Aluminum foil covering Aluminum foil covering, leaving a hole of 6--8 m m

12 7'

19 9

12

20

'Significantly different from the control at

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plants. However, leaving a small hole in the cover was a d e q u a t e to restore the shoot-renewal potential. 4. - - T h e m i n i m a l l i g h t i n t e n s i t y o n t h e g r a f t u n i o n r e q u i r e d f o r r e n e w a l shoots f o r m a t i o n was studied. F o r t y - t w o ' M e r c e d e s ' p l a n t s w e r e p r u n e d 8 0 c m a b o v e t h e soil o n 2 A p r i l , leaving one main stem per plant. The graft unions were covered with different numbers of transparent polyester sheets (Reemay, Dupont). An additional g r o u p was covered w i t h a l u m i n u m foil a n d in still a n o t h e r g r o u p of p l a n t s t h e u n c o v e r e d g r a f t u n i o n s w e r e s p r a y e d w i t h 1 0 0 0 m g 1-' s o l u t i o n o f N A A . A n u n t r e a t e d g r o u p o f p l a n t s was l e f t as a c o n t r o l . T h e p l a n t s i n all t r e a t ments were continuously de-shooted. There were 6 plants per treatment. The l i g h t i n t e n s i t y a b o v e a n d u n d e r t h e c o v e r s was m e a s u r e d b y l i g h t m e t e r L i C O R L i - 1 8 5 A. A f t e r 53 d a y s o f d e - s h o o t i n g , t h e c o v e r s w e r e r e m o v e d a n d t h e n u m b e r s of r e n e w a l s h o o t s c o u n t e d . F r o m the results ( T a b l e IV), it can be seen t h a t t h e r e d u c t i o n i n l i g h t b e l o w 2 5 0 w m -2 ( 1 4 0 0 0 l u x ) l e d t o a d e c r e a s e i n t h e

Experiment

TABLE IV Effect of shading and NAA treatment on the formation of the basal renewal shoots from the graft union of 'Mercedes' roses. Six plants per treatment Treatment

Control -- no covering 1 layer of polyester 2 layers of polyester 4 layers of polyester 8 layers of polyester Aluminum foil covering NAA, 1000 mg 1-~ spray

Light above the graft u n i o n Lux

Watt m -~

Microeinstein m -~ s-'

27 20 14 9 4

280 250 250 150 80

430 320 230 140 90

280

430

000 000 000 000 000 0 27 000

Number of plants ~ renewed out of 6

Total number of renewal shoot per treatment

6 6 6 5 3 2 1

18 21 26 12 8 2 2

72 n u m b e r of renewals from 4.3 per plant to only 2.4 per plant. A further reduction in light intensity decreased the number of plants with cane renewal. Complete exclusion of light from the graft union markedly reduced the formation of renewal shoots, and similar results were obtained with NAA 1000 mg 1-2. DISCUSSION The development of vigorous shoots from the basal parts of plants is n o t restricted to roses, b u t is c o m m o n to many w o o d y plant species. These shoots, if juvenile, have a high rooting-potential and a low flowering-ability (Dermen, 1948; Zimmermann and Brown, 1971; Tubbs, 1974). In most of the fruit and ornamental trees, the formation of these vigorous juvenile-like shoots have a negative economic and aesthetic value (Harris et al., 1971; Larue et al., 1974; Boswell et al., 1976; Dozier and Hollingsworth, 1976). In rose plants, those shoots also have a vigorous habit of growth. However, they have a relatively large terminal inflorescence and therefore are not juvenile. Contrary to other plants, the formation o f these shoots is very desirable (Byrne and Kohl, 1972; Zieslin et al., 1973). Various factors and practices such as drying of plants, i.e. water stress (Post, 1952), irrigation regimes (Plaut and Zieslin, 1974), light intensity (Fisher and Kofranek, 1949) and artificial lighting (Carpenter and Rodriguez, 1971a; Carpenter and Anderson, 1972; Khosh-Khui and George, 1977), pruning (Smith and Kohl, 1970), bending (Faber and White, 1977; Zieslin and Halevy, 1978) and cooling (Biran and Zieslin, 1973; Hana, 1979), as well as chemical treatments, particularly with cytokinins (Carpenter and Rodriguez, 1971b; Parnps, 1 9 7 1 ; Faber and White, 1977; Ogava, 1979) and ethephon (Zieslin et al., 1972), are known to be involved in the stimulation of renewal shoot formation in roses. This was also achieved by complete removal of lateral growth (Kohl and Smith, 1969; Zieslin et al., 1976), as has also been s h o w n i n trees (Dermen, 1948). All the above-mentioned treatments, including de-shooting, can be attributed to sink removal, cessation of growth and the diversion of translocation metabolites towards the lower plant parts. Indeed, the de-shooting caused a remarkable increase in the weight of the rose root system (Zieslin and Mot, in preparation). However, the stimulating effect of de-shooting was limited by unfavourable environmental conditions. De-shooting of plants growing during the summer in an uncooled greenhouse did n o t enhance the number of " b o t t o m breaks" (Table I). Cooling alone increased the cane renewal to some extent, b u t de-shooting combined with cooling resulted in renewal of almost 75% of the plants with more than 2 breaks per plant. The plant response after the transfer to the evaporative-cooled greenhouse emphasized the need for favourable environmental conditions for rose cane renewal. While 57% of transferred plants showed renewal, with 1.6 breaks per plant, only 28% of those plants left in the uncooled greenhouse showed " b o t t o m breaks".

73 Under the conditions of our experiment, it was impossible to separate the effect of the low temperature from t h a t of relative humidity. Relative h u m i d i t y is also k n o w n to be a factor stimulating basal lateral shoot develo p m e n t (McIntyre, 1977). A lack of response to treatments stimulating cane renewal during certain periods of the year has been shown with the application of benzyladenine (Ogava, 1979) and with cooling-treatments (Schrock and Hanan, 1981). In the latter case it was attributed to the variation in the content of nonstructural carbohydrates in the plants. An additional environmental factor f o u n d to be involved in cane renewal is the light intensity (Tables II--IV). A possible light involvement in the formation of " w a t e r sprouts" on the trunks of forest trees was also indicated when forest trees were thinned (Kozlowski, 1971). The data presented in Table IV show t h a t cane renewal was decreased by more than 50% when the light intensity was reduced to 80 w m -2. Thus, the shade conditions existing under the rose plant canopy can be one of the factors affecting the scarce development of renewal shoots, It might be possible t h a t the rise in the n u m b e r of " b o t t o m breaks" after severe pruning or bending is partially by the exposure of the stem base to light. The canopy shading is also characterized by changes in the spectral composition o f light (Kasperbauer, 1971). Although this factor has n o t been tested in the present study, different effects of red and far-red light on rose renewal have recently been shown by H.F. Wilkins (Minnesota State University, personal communication, 1980). The decrease in bud break following darkening of the lower stem either with or w i t h o u t foliage (Table II), and the appearance of " b o t t o m breaks" when a small hole was left in the cover (Table III), suggest the possible perception of the light stimulus in the buds or by the buds producing tissue, as was reported for d o r m a n t buds in peach trees (Erez et al., 1966). A similar response was reported in olive trees, where the tree base was covered with black polyethylene to prevent development of " w a t e r sprouts"; a practice c o m m o n in California (Hartmann and Opitz, 1966). It is also possible that the effect of darkening of the stem base is related to the influence of light on the pattern of translocation of metabolites recently described in rose plants (Mot and Halevy, 1980). One single spray of 1000 mg 1-1 of NAA solution was sufficient to prevent the appearance of " b o t t o m breaks" (Table IV). This response to NAA and other NAA derivatives is c o m m o n in fruit and ornamental trees (Harris et al., 1971; Larue et al., 1974; Boswell et al., 1976; Dozier and HoUingsworth, 1976).

REFERENCES Biran, I. and Zieslin, N., 1973. The effect of cooling on the rose bud sprouting. Annu. Rep. Dep. Ornamental Hortic., The Hebrew Univ., 1972/73, pp. 125--127.

74 Boswell, S.B., McCarty, C.D., Ede, L.L. and Chesson, J.H., 1976. Effect of single application of naphathalene acetic acid on yield and shoot growth of young lemon trees. HortScience, 11:222. Byrne, T. and Kohl, H.C., 1972. Rose plant renewal and prevention of leaf drop. Roses Inc. Bull., March, pp. 37--39. Carpenter, W.J. and Anderson, G.A., 1972. High intensity supplementary lighting increase yields of greenhouse roses. J. Am. Soc. Hortic. Sci., 97: 331--334. Carpenter, W.J. and Rodriguez, R.C., 1971a. Supplemental lighting effects on newly planted and cut-back greenhouse roses. HortScience, 6:207--208. Carpenter, W.J. and Rodriguez, H.C., 1971b. The effect of plant growth regulating chemicals on rose shoot development from basal and axiUary buds. J. Am. Soc. Hortic. Sci., 96:389--391. Dermen, H., 1948. Chimeral apple sports and their propagation through adventitious buds. J. Hered., 39:235--245. Dozier, W.A. and Hollingsworth, M.H., 1976. Sprout control of apple nursery stock with NAA. HortScience, 11: 392--393. Erez, A., Samish, R.N. and Lavee, S., 1966. The role of light in leaf and flower breaking of the peach (Prunuspersica). Physiol. Plant., 19:650--659. Faber, W.R. and White, J.W., 1977. The effect of pruning and growth regulator treatment on rose plant renewal. J. Am. Soc. Hortic. Sci., 102:223--225. Fisher, C.N. and Kofranek, A.M., 1949. Bottom break production of rose plants as influenced by plot location in the greenhouse. Proc. Am. Soc. Hortic. Sci., 53:501--502. Halevy, A.H. and Kohl, H.C., 1971. Rose plant renewal and branching. Roses Inc. Bull., May, pp. 28--30. Hanan, J., 1979. Split temperatures and rejuvenation in roses. J. Am. Soc. Hortic. Sci., 104:37--40. Harris, R.W., Sachsl R'MI and Fissell, R.E., 1971. Control of trunk sprouts with growth regulators. Calif. Agric., 25:11--13. Hartmann, H.T. and Opitz, K.W., 1966. Olive production in California. University of California Div. Agric. Sci., Circ. 540, pp. 2--27. Kasperbauer, M.J., 1971. Spectral distribution of light in a tobacco canopy and effects of end of day light quality on growth and development. Plant. Physiol., 47:775--778. Khosh-Khui, M. and George, R.A.T., 1977. Responses of glasshouse roses to light conditions. Scientia Hortic., 6:223--235. Kohl, H.C. and Smith, E.D., 1969. Rose plant renewal. Roses Inc, Bull., April, pp. 18--20. Kozlovski, T.T., 1971. Growth and Development of Trees. Vol. I. Academic Press, London, New York, pp. 197--199. Larue, J.H., Sibbett, G.S., Bailey, M.S., Fitch, L.B., Yeger, J.T. and Gerdts, A., 1974. NAA sprout inhibition shown in olives, pomegranates, prunes, plums and walnuts. Calif. Agric., 28:18--19. McIntyre, G.I., 1977. Environmental control of lateral bud growth in the sunflower (Helianthus annuus). Can. J. Bot., 2673--2678. Mor, Y. and Halevy, A.H., 1980. Promotion of sink activity of developing rose shoots by light. Plant Physiol., 66:990--995. Ogava, R., 1979. Promotion of renewal canes in greenhouse roses by 6-benzylaminopurine without cut back. HortScience, 14:612--613. Parups, E.V., 1971. Use of 6-benzylaminopurine and adenine to induce b o t t o m breaks in roses. HortScience, 6:456--457. Plaut, Z. and Zieslin, N., 1974. Productivity of greenhouse roses following changes in soil moisture and soil air regimes. Scientia Hortic., 2:137--143. Post, K., 1952. Florist's Crop Production and Marketing. Orange Judd, New York, pp. 758--803.

75 Schrock, D. and Hanan, J.J., 1981. The effect of low temperature on yield and renewal cane production in relation to carbohydrate levels in roses. Scientia Hortic., 14: 69--76. Smith, E.D. and Kohl, H.C., 1970. Effect of height of cut-back on subsequent stimulation of rose renewal canes. Roses Inc. Bull., March, pp. 19--21. Tubbs, F.R., 1974. Problems of juvenility in woody perennials. Chron. Hortic., 14:27--28. Zieslin, N. and Halevy, A.H., 1978. Components of axillary bud inhibition in rose plants. III. Effect of stem orientation and changes of bud position on the stem by budding. Bot. Gaz., 139:60--63. Zieslin, N., Halevy, A.H., Mor, Y., Bachrach, A. and Sapir, J., 1972. Promotion of renewal canes in roses by ethephon. HortScience, 7:75--76. Zieslin, N., Halevy, A.H. and Biran, I., 1973. Sources of variability in greenhouse rose flower production. J. Am. Soc. Hortic. Sci., 98:321--324. Zieslin, N., Mor, Y., Bachrach, A., Haaze, H. and Kofranek, A.M., 1976. Controlling the growth and development of rose plants after planting. Scientia Hortic., 4:63--72. Zimmermann, M.H. and Brown, O.L., 1971. Tree Structure and Function. Springer Verlag, Berlin, Heidelberg, New York, pp. 138--143.