N. Zieslin

Light on roses. A review.

Abstract Light intensity is the most important factor affecting rose plant growth and flowering. Decrease in light intensity and the duration of the light period owing to seasonal changes or shading reduce the yield of roses. Different components of productivity and quality, such as bud breaking, rate of flower abortion, formation of renewal shoots, time period between harvests, length, weight and diameter of stem and flower buds, leaf area and pigmentation of petals are affected by light. Supplementary lighting of relatively high levels of irradiance, especially during periods of low solar radiation, results in increasing numbers of flowers. A survey of reports on the influence of light, either natural or artificially supplied, on the various aspects of rose growth, productivity and flower quality is the purpose of the present review.

Flower bud atrophy in ‘Baccara’ roses. II. The effect of environmental factors

Abstract The effect of several environmental factors on flower bud atrophy in ‘Baccara’ roses was studied. Reduction of air or soil temperature caused an increase in flower bud atrophy. Reduction in light intensity increased “blindness” in relation to shading intensity. Shading of only the young developing shoot also greatly increased flower atrophy. Continuous shading had a cumulative effect in increasing “blindness”. However, removal of shade caused an immediate increase in flowering to a rate comparable to unshaded control. Photoperiod had no effect.

Improvement of postharvest keeping quality of 'Mercedes' roses by gibberellin.

Postharvest ‘pulsing’ for 20 h with solutions containing 20 to 40 mgl-` of gibberellic acid (GA3) extended the vase life and promoted bud opening of unstroed and stored flowers of rose cv. Mercedes, while continuous treatment with GA3 was detrimental. The fresh and dry weights and the water content of petals of GA3-treated flowers during the vase-life period were higher than in flowers treated with deionized water or preservative solution. The effect of GA3 on flower longevity was even more pronounced with cold-stored flowers. Ethylene evolution from detached petals of unstored and stored flowers was promoted by GA3. Unlike the effect of cv. Mercedes, GA3 did not affect flower longevity of five other rose cultivars tested, but in all of the tested cultivars the longevity of detached petals was extended by treatment with GA3.

The effects of various night-temperature regimes on the vegetative growth and fruit production of tomato plants

Abstract The fruit production of tomato cultivar ‘Moneymaker’ was not reduced by interruption of the optimal night-temperature regime by short intervals of lower temperature. The same treatment increased the yield of ‘Cherry’ by 82% in the comparison with a constant night temperature of 18°C. The increase in yield of this cultivar was due to a larger number of fruits per plant. Interruption of the optimal night-temperature regime by a pulsing temperature regime (PTR) may be introduced as a method in the cultivation of greenhouse tomato plants for energy saving and for promotion of fruit-set in certain tomato cultivars.

Responses of rose plants cultivar «Sonia» and Rosa indica major to changes in pH and aeration of the root environment in hydroponic culture

Abstract Roots of a rose cultivar ‘Sonia’ and a rose rootstock Rosa indica major were both able to reduce the pH of a nutrient solution containing ammonium. Root growth was inhibited when plants were exposed to either pH 8 or pH 4 solutions in comparison with plants grown in solution of pH 6. Plant growth, leaf size and content of chlorophyll were not affected in plants at pH 4, while all these variables were reduced at pH 8 in comparison with plants grown at pH 6. After 4 days in solution of pH 8 the leakage of electrolytes from ‘Sonia’ roots was significantly higher than that from roots of R. indica while at pH 6 no differences were observed. The inhibition of growth of ‘Sonia’ by high pH was prevented by grafting on a R. indica rootstock, however leaf chlorosis was not prevented. The primary roots of ‘Sonia’ plants deteriorated completely after 11 days in the high pH solution. During this period roots of R. indica only showed symptoms of partial necrosis. The adventitious roots formed after the decay of the primary roots were more tolerant to the high pH but a decrease in the chlorophyll content was still noted. The growth of both cultivars was significnatly reduced when grown in stagnant nutrient solutions with an uncontrolled pH, without forced aeration. When pH 6 was constantly maintained, the inhibition of growth caused by insufficient aeration was partially prevented. The acidification capacity and tolerance to high pH conditions are proposed as desirable characteristics in breeding of rose cultivars and rootstocks.

Shoot-root interaction effects on nitrate reductase and glutamine synthetase activities in rose (Rosa × hybrida cvs. Ilseta and Mercedes) graftlings

Summary Flower formation in greenhouse roses ( Rosa × hybrida ) is generally promoted by grafting on various rootstocks rather than propagating ungrafted plants from cuttings. The number of flowers per plant in roses is also positively correlated with the nitrogen content in the nutrient solutions as well as by ammonium ion proportion of the total nitrogen. It could be, therefore, that the differences among the effects of various root systems on flower formation in rose plants are associated with differences in assimilation of nitrogen, in either nitrate or ammonium-forms or both. This assumption was examined by measurements of the nitrate content as well as of the nitrate reductase (NR) (E.C. 1.6.6.1) and glutamine synthetase (GS) (E.C. 6.3.1.2) activities in roots and leaves of 6-week-old plants propagated from cuttings (own-root plants) or graftlings, i.e., concomitantly grafted and rooted roses cvs. Mercedes, Ilseta or Rosa indica major, used as understocks. The data obtained showed that the nitrate contents in the roots of cuttings were higher than those in the leaves, whereas that in the roots of R. indica was higher than those in roots of the two cultivars. The content of NO 3 − in roots and leaves of the graftlings was affected by the grafting procedure and was in good agreement with the nitrate reductase activity in plant organs. The activity of nitrate reductase in the leaves of cuttings was higher than in their roots, whereas in graftlings, its activity was promoted in the roots and inhibited in the leaves, in all scion-root combinations. Glutamine synthetase activity in roots and leaves of either cuttings or graftlings was 4–5 orders of magnitude higher than NR activity. Similar to NR activity, GS activity in the leaves of own-root plants was higher than that in their roots. However, unlike the NR activity, GS activity in roots and leaves of the graftlings was not markedly altered following the grafting procedure.

Plant management of greenhouse roses. Formation of renewal canes

Abstract Renewal shoot (“bottom break”) formation in rose plants was affected by the temperature and relative humidity 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.

The influence of moisture regime on greenhouse rose production in various growth media

Abstract The effect of irrigation regimes and growth media on the production and quality of ‘Baccara’ roses was examined in a greenhouse during the 1969/70 and 1970/71 seasons. The media tested were (a) sandy loam, (b) sandy loam mixed with peat moss, (c) vulcanic scoria (tuff), (d) sandy loam placed on top of the local soil; all except (d) were in raised benches. Two levels of fertilizers were examined in the tuff media. The irrigation treatments in the soil media were established according to pre-irrigation water suction in the range 5 to 50 centibars (cb). In the tuff media the irrigation treatments were scheduled at different frequencies ranging from eight irrigations per day to one irrigation every 2–3 days. Maximum flower production was obtained in sandy loam which was placed on top of the local soil and irrigated so that the soil water suction did not rise above 5 cb. Flower length was unaffected by the irrigation regime in this growth medium. Flower production in the raised benches dropped when the water suction was kept below 20 cb or when it was allowed to rise to 50 cb. On the other hand, the highest percentage of long-stem flowers was obtained when the water suction was maintained below 5 cb. No significant difference in flower production was found between 5–8 and 2 irrigations per day in the tuff media. Maximum yield from these treatments was significantly lower than that in the non-raised soil benches. An increase in fertilizer level had no effect on flower production or quality. The flowering buds were relatively small at the beginning of winter and became larger toward spring. Only minor effects of growth media and moisture regimes on bud weight were found.

GA3 Effects on Postharvest Alterations in Cell Membranes of Rose (Rosa x Hybrida) Petals

Summary The postharvest increase in leakage of electrolytes from detached petals of rose flowers cvs. Mercedes, Sonata, and Golden Times, was suppressed following inhibition for 24 h in 20 mg L -1 solution of GA 3 , while leakage from petals of cv. Madelon was not affected by the GA 3 treatment. Similar suppression of leakage was also present when flower buds of cvs. Mercedes and Sonata were sprayed with 350 mg L -1 (1mM) solution of GA 3 . Postharvest decline of cell membrane fluidity and, to a larger extent, the decrease in membrane protein content were also suppressed following GA 3 application. In both control and GA 3 -treated petals, the decrease in membrane fluidity preceded the increase in ion leakage. The timecourse of this decrease coincided well with the time-course of the increase in membrane permeability in the control petals, but not in the petals from GA 3 -treated flowers. On the other hand, the time-course of the increase in membrane permeability corresponded well with the decrease in content of membrane protein in both control and GA 3 -treated petals. The decrease in content of total protein in petals of GA 3 -treated flowers was lower than that of control flowers. Comparison of electrophoretic protein profiles from both control and GA 3 -treated petals showed that the postharvest decomposition of proteins was inhibited by the GA 3 -treatment. The involvement of gibberellins in maintaining membrane integrity of rose flowers is discussed.

Controlling the growth and development of rose plants after planting

Abstract The effects of pinching and lateral bud removal (deshooting) on the development of structural shoots, the number of flowers, and the average flower stem length in young rose plants were examined, using the cultivars ‘Baccara’, ‘Sonia’ and ‘Belinda’. The effect of deshooting on flower yield varied with each cultivar. It did not affect the number of ‘Baccara’ flowers, but increased ‘Sonia’ and ‘Belinda’ flower production by 50% and 75%, respectively. Leaving flowers to bloom out on plants before the start of commercial harvest resulted in a decrease in the length of the flower stems and also reduced the beneficial effect of deshooting on flower yield. Deshooting enhanced structural shoot formation (“bottom breaks”). Pinching flower buds of structural shoots increased the number of ‘Baccara’ flowers in comparison with pruning these shoots to 40–60 cm, as in common practice. Deshooting of the structural shoots of ‘Sonia’ and ‘Belinda’ increased the number of flowers in both cultivars.