Submerging `Stayman' apples in nonionic and anionic surfactant-water solutions caused increased water uptake and fruit cracking. The primary sites of water uptake were lenticels and injured areas of the fruit cuticle. Fruit cracking caused by submerging fruit in 1.25 ml X-77/liter surfactant was used to predict the natural cracking potential of `Stayman' strains and apple cultivars in the field. Submerging apples in aqueous pesticide mixtures did not Increase fruit cracking or water uptake. Fruit cracking and uptake of surfactant-water were not correlated between apple cultivars. In a surfactant-water bath, `Starkrimson Delicious' absorbed more water than `Stayman', `York', `Jonathan', and `Golden Delicious'; no `Starkrimson Delicious' fruits cracked, but 32% to 80% of the other cultivars did. In field tests, four airblast spray applications of GA4+7 in July and Aug. 1987 reduced fruit cracking from 56% to 21%, and five applications In July, Aug., and Sept. 1988 reduced fruit cracking from 93% to 75%. In 1987, daminozide reduced cracking, but, in 1988, neither daminozide, NAA, nor Vapor Gard alone reduced cracking. However, in 1988, a combination treatment of GA4+7, daminozide, NAA, and Vapor Gard reduced fruit cracking from 93% to 22%. Also, two scorings of the trunk with a carpet knife reduced fruit cracking 22%. Chemical names used: alkylaryl polyoxyethylene alcohol glycol (X-77); butanedioic acid mono(2,2-dimethylhydrazide) (daminozide); naphthaleneacetic acid (NAA); di-1-p-methene (Vapor Gard); gibberellic acid (GA4+7).
R.E. Byers, D.H. Carbaugh, and C.N. Presley
Rodney B. Jones, Margrethe Serek, and Michael S. Reid
The vase life of cut sunflowers given a simulated transport period (3 days dry storage at 8C) was significantly enhanced by a l-hour pulse with 0.01% Triton X-100 administered before storage. The Triton pulse increased solution uptake during the l-hour pulse, decreased fresh weight loss during dry storage, and significantly improved water uptake thereafter, resulting in greater leaf turgidity and longer vase life. Leaf stomata] conductance measurements indicated that Triton X-100 maintained stomatal opening at a higher level during the pulse and after storage, but had no effect during dry storage. Chemical name used: octylphenoxypolyethoxyethanol (Triton X-100).
T. Venkatarayappa, M. J. Tsujita, and D. P. Murr
Cut flowers of rose (Rosa hybrida L. cv. Samantha) exhibited a longer vase life when opened in solutions containing cobaltous ion (Co2+). The extended vase life in response to Co2+ was related to 1) an increased water uptake into the cut flower, 2) an improved water balance during opening, 3) a delay in loss of fresh weight, and 4) a prevention of the occurrence of bent-neck. A concentration of 1.5 mm Co2+ gave maximum beneficial effects without injury to the cut flower, while a 2.0 mm concentration induced some toxic symptoms on leaves.
Dominic J. Durkin
Millipore filtration of water was shown to accelerate the rate of hydration of rose peduncle tissue. In a stress test, aeration of deionized water decreased the rate of peduncle hydration, while millipore filtration of aerated water increased hydration rates. Solution acidification enhanced the rate of hydration, and the addition of sucrose to the solution significantly retarded hydration. Flower stems recut under deionized water hydrated as quickly as those recut in air and placed in millipore-acidified water. Flower stems recut in air and placed in deionized water hydrated slowly. These results suggest that air blockage in the cut rose stem reduces the rate of water uptake.
D. F. Hamilton and P. L. Carpenter
An examination of dormancy in seeds of Eastern Redbud, Cercis canadensis L., showed that dormancy is controlled by permeability of the testa. Scarification by H2SO4 or mechanical abrasion permitted rapid and complete germination of dormant seed. Stratification was necessary only if seed were not scarified. Nonscarified seeds showed almost no water uptake during 55 days at 5°C, while scarified seeds had a steep imbibitional gradient. Germination was not stimulated by adding oxygen. No growth inhibitors were detected in dormant seed, and no promoters were found in chilled seeds.
B. Yaron, N. Zieslin, and A. H. Halevy
One year old ‘Baccara’ roses budded on Rosa chinensis cv. ‘Major’ were planted in large containers and irrigated for 90 days with water containing various salinity levels (ca. 0.4 to 7.8 EC × 103). Salinization was obtained by either chloride or nitrate salts. Irrigation with water containing chlorides was more detrimental than with water containing nitrates at the same level of salinity. Stem and leaf growth and water uptake decreased with increasing soil salinity. A slight decrease was noticed even at 2.0 mmhos/cm, containing chlorides, the damage increasing with time, indicating a cumulative effect of soil salinity even at low salinity level.
A polymer-based antitranspirant was compared to a fungicide, Acti-Dione PM for control of Erysiphe cichoracearum on Zinnia elegans and its effects on plant growth. Plants treated with the antitranspirant had a significant increase in height, fresh and dry weight, and length of the flowering period. In addition, the antitranspirant treated plants had significantly reduced powdery mildew. SEM studies showed that the antitranspirant treated plants had closed stomata, and presumably this had an effect on water uptake as well as the plant host interactions.
A. E. Einert
The effects of several concn of growth retardant chemicals on the elongation of the last stem internode of cut tulips were studied. Compared to tap water, α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidine-methanol (ancymidol) at 25 ppm reduced intemode growth by 31% with no detrimental effects on vase life or flower quality. The 2,4-dichlorobenzyl-tributylphos-phonium chloride (CBBP) was ineffective at 6-25 ppm. CBBP at 125 did reduce stem elongation but was toxic to the flower. Ancymidol in the vase solution retarded growth without altering water uptake by the stem.
Damien de Halleux and Laurent Gauthier
Transpiration and water uptake play an important role in the growth of horticultural crops, such as tomatoes. Water uptake ensures the transport of nutrients. However, the transpiration rate is affected by the humidity level in the greenhouse. High levels of humidity restrict transpiration and lead to fungal diseases resulting in yield losses. Under northern latitudes, using more airtight structures combined with high levels of artificial lighting increase the humidity level inside the greenhouses. To decrease humidity, growers have to dehumidify by ventilating and heating at the same time, leading to increased energy consumption. However, to our knowledge, the literature does not report on the energy consumption needed to dehumidify. To evaluate this energy consumption, we used a greenhouse simulation model of heat and mass exchanges integrated into a general greenhouse control and management software system (GX). Evapotranspiration, condensation on the cladding, and infiltration and ventilation rates were taken into account for the water balance. Based on 1 year of climatic data, three sets of simulation were realized: 1) no dehumidification; 2) standard dehumidification by ventilation and heating; 3) dehumidification with heat exchangers. Results indicate that for an acceptable level of humidity within a greenhouse tomato crop (vapor pressure deficit >5 kPa), the energy consumptions with standard dehumidification and with heat exchangers are 25% and 15% higher, respectively, than without dehumidification. These results are being used to establish recommendations for the management of humidity under northern latitudes.
William H. Rein, Robert D. Wright, and John R. Seiler
Stem cuttings of Blue Rug juniper (Juniperus horizontalis Moench `Wiltonii'), `Hino-Crimson' azalea [Rhododendron (Lindl.) P1anch `Hino-Crimson'], and `Helleri' holly (Ilex crenata Thunb. `Helleri') were propagated in 1 peat: 1 perlite (v/v) at one of five moisture levels based on medium dry weight (125%, 250%, 375%, 500%, or 625%). Cutting survival and percentage of rooted cuttings were highest at the highest medium moisture level in all three species. Incidence of cutting basal rot was not directly related to medium moisture level, but more to the growth stage of the stock plant. Midday xylem water potential (ψ) of cuttings for each species was highest in the wettest propagation medium and lowest in the driest medium. During propagation, stem cutting ψ below - 2.0 MPa occurred even in the wettest medium tested, and frequently reached - 4.0 MPa in cuttings in the driest treatment (125%). Basal water uptake by cuttings was highest in the wettest medium moisture level. Water uptake was highest during the first few days after insertion, and thereafter decreased until root emergence.