Use of shading nets to improve quality characteristics of compact gardenia (Gardenia jasminoides ellis) potted plant

The quality of compact gardenia potted plants is characterized by plants' shape, number of flowers and leaves' color. These characteristics are related mainly to photoperiod and light intensity. The effect of shading, by means of shading nets, on quality characteristics of compact gardenia potted plants was investigated during summer in a polyethylene covered greenhouse located near Volos, on the coastal area of Central Greece. Shading nets with 70% (30% shading) and 40% (60% shading) light transmission coefficient were used inside the greenhouse that was already shaded by white paint and had a total light transmission coefficient of 30%. Gardenia plants were grown under the above shading nets and under ambient greenhouse conditions from April to July 2010. Measurements of plant growth and development characteristics were carried out along with microclimate measurements. The results showed that plants placed under 30 and 60% shading nets were 10 and 13% shorter than the plants grown under ambient greenhouse conditions, respectively. Furthermore, shaded plants grown under the 30 and 60% shading nets had 23 and 45% lower leaf area and fresh weight than the plants grown under ambient greenhouse conditions, respectively. Finally, it was found that plants grown under the 60% shading net had more vivid green color compared to the rest of the plants

Estimation of water needs of young and aged rose plants with the use of two simplified transpiration models

Water needs of a soilless rose crop during a growing period, may alter significantly depending on plant growth stage and cultivation treatments. However, simplified transpiration (Tr) models, are not tested after rapid change of crop’s leaf area (LA) due to specific cultivation treatments. The aim of this work was to estimate the water needs of rose plants (‘Miss Piggy’) cultivated in a closed hydroponic system, after planting, pruning, harvesting and bending. For this purpose, plants Tr and LA were measured on young plants after planting and on mature plants after pruning, harvesting and bending. At the same time plants Tr was estimated based on simplified models by Penmann-Monteith, according to greenhouse climate parameters and crops leaf area index (LAI). The LA of young plants varied from 0.003 to 0.013 m2 plant-1 while their Tr from 0.008 to 0.046 g m-2 day-1 during the two months period. Mature plants LA ranged from 0.16 to 0.37 m2 plant-1 and their Tr from 0.25 to 1.36 g m-2 day-1 during the same period. LAI in young plants increased constantly from 0.022 to 0.1, while LAI in mature plants altered depending on the treatments (pruning, harvesting and bending). However even after pruning, both Tr and LA of mature plants increased (more than 10 times) in comparison to those of young plants during the two months’ period. The results from the above mentioned measurements show that, young and mature plants Tr was overestimated by model that did not take into account LAI alteration after pruning, harvesting and bending treatments, although it responded efficiently when plants LA remained almost stable during the cultivation period. The model that included LAI, fitted well when plants LA reduced significantly after the above mentioned treatments. None of the transpiration models estimated the Tr of young plants correctly. © 2020 International Society for Horticultural Science. All rights reserved

Water and fertilizers use efficiency in grafted and non grafted tomato plants on soilless culture

The improved rooting environment and the absence of pathogens in substrates used in soilless cultures, make the use of grafted plants unnecessary when grown hydroponically. The worldwide water shortages and the increased environmental pollution indicate the use of any technique that increases the production with the highest possible water and fertilizers use efficiency. In this work water use efficiency (WUE) and fertilizer use efficiency (FUE) in agronomical and biological terms (g marketable fruit and g dry matter per litre of transpired water and g of absorbed nutrients, respectively) have been determined on non grafted 'Big Red' tomato plants (Lycopersicon esculentum Mill.) as well as 'Big Red' plants grafted on 'Big Red' and 'He-mans' rootstock. Plants were grown in an open hydroponic system. Measurements of leaf area and transpiration and nutrient concentrations in shoots, leaves and fruits as well as plants fresh and dry weight were performed on grafted and non grafted plants. The results indicate that non grafted tomato plants had 25 to 44% higher leaf area (and for this reason the highest water consumption) and 30% higher shoot and leaf dry weight compared to the grafted plants. In contrast grafted plants had 31 to 39% higher fresh fruit production. Finally grafted plants had 50 and 48% higher WUE and FUE, respectively, compared to non grafted plants as the latter consume more water and nutrients on unmarketable biomass (shoots and leaves)

Nutrient solution management recirculating soilless culture of rose in mild winter climates

In a closed hydroponic system with a rose crop, the composition of the nutrient solution in the tank was measured every two days in order to establish the dynamics of the nutrient elements in short-term periods. It was observed that the concentration of Fe decreased very fast and that the concentrations of Ca2+, Mg2+ and Cl- increased. The concentrations of K+, Ca2+ and SO4 2- did not reach critical levels. The Cl- content of commercial fertilizers was measured and it was concluded that the addition of some fertilizers (e.g, Fe-EDDHA) would lead to an accumulation of Cl- in the nutrient solution. Thus, Cl- free fertilizers should be used. The analysis of the Fe, NH4 and PO4 balance in the nutrient solution seems to be required to determine the necessary corrections to increase the life span of the nutrient solution

Calcium, magnesium and potassium concentrations prediction in a recirculated nutrient solution of a greenhouse soilless rose crop

The effects of i) biophysical processes such as crop water uptake, and elements absorption and ii) chemical processes such as fertilizers dissolution and pH changes, on Ca2+, Mg2+ and K+ concentration in a recirculated nutrient solution of a greenhouse soilless rose crop (Rosa hybrida 'First Red'), were studied. Measurements of greenhouse microclimate variables, crop water uptake as well as pH, EC and Ca2+, Mg2+ and K+ concentration in nutrient solutions kept in storage tank or applied for crop fertigation, were carried out during autumn 2001. The results showed that variations of Ca2+ concentration in the nutrient solution were highly correlated to crop water uptake, crop Ca 2+ absorption, fertilizer dissolution and pH variation of the nutrient solution. The concentration of Mg2+ in the nutrient solution was correlated to EC of the solution. Equations for Ca2+, Mg 2+ and K+ concentrations prediction in the recycled nutrient solution were developed and calibrated. Validation gave satisfactory results

Alteration of NO - 3, PO 3- 4 and SO 2- 4 Concentration on rose plants in response to greenhouse climate parameters and their concentration in the nutrient solution

The objective of this work was to quantify temporal changes of NO - 3, PO 3- 4 and SO 2- 4 concentration on leaves, shoots and roots of rose plants during a short growing period, in response to air temperature, light intensity and the concentration of the above mentioned anions in the nutrient solution. For this reason rose plants (×Rosa hybrida 'Iceberg') were placed in a glasshouse during September 2004 and grown in nutrient solution according to the Deep Flow Technique (DFT). The plants were pruned in order to develop one main flower shoot. Measurements were performed during December 2004. The concentration of NO - 3, PO 3- 4 and SO 2- 4 (mg L -1) in the nutrient solution and in different plant parts (mg kg -1) as well as the fresh (fw) and dry (dw) weight of leaves, shoots and roots were measured every day, by destructive sampling of 6 plants each time, for a period of 28 days. In addition during the same period the greenhouse air temperature and the intensity of the incoming solar radiation were continually recorded. The concentration of NO - 3 and PO 3- 4 in leaves was significantly affected by i) the intensity of the incoming solar radiation and ii) the concentration of NO - 3 and PO 3- 4 in the nutrient solution. The concentration of NO - 3 and PO 3- 4 in shoots was affected by the above mentioned parameters and by the greenhouse air temperature. Alteration of NO - 3 concentration in the nutrient solution causes an instant alteration of NO - 3 concentration in leaves and a delayed alteration of NO - 3 concentration in shoots. In contrast, alteration of PO 3- 4 concentration in the nutrient solution causes a delayed alteration of PO 3- 4 concentration in both leaves and shoots. The concentration of NO - 3 and PO 3- 4 in roots and SO 2- 4 in shoots and roots was not strongly related to the above mentioned greenhouse climate parameters and the concentration of NO - 3, PO 3- 4 and SO 2- 4 in the nutrient solution

Chrysanthemum morifolium response to PAR intensity as indicated through electrical signal

It is well documented that higher plants respond to environmental stimuli producing electrical signals that are in practise the information carriers in intracellular and intercellular communication. Since the amplitude of the biosignal can give only indistinct information about plant reaction, helping to distinguish when plant remain in a normal or in a stimulated situation, it is unable to answer what stimuli causes plant's reaction and the electrical signal generation. In order to relate plant electric wave signals characteristics to solar radiation (400 to 1100 nm) and PAR (400 to 700 nm), measurements were performed on a single stem chrysanthemum plant. All measurements were conducted in Faraday cage in order to avoid electronic noise from external sources. The electrical signals from chrysanthemum (Chrysanthemum moriflorum) plant were detected through an advanced measuring data acquisition system, included Ag/AgCl electrodes, which were placed on plant leaves. The amplitude of the electrical signal (v), solar radiation intensity (W m-2) and PAR (μmol s -1 m-2) in leaves level as well the temperature (°C) and the humidity (%) of the air inside the Faraday cage were measured. The results revealed that electrical signal amplitude alteration related more to PAR than to incoming light intensity variation. In addition electrical signal spectrum analysis showed that a specific group of frequencies are responsible for the increase of electrical signal amplitude, occurred during plant shading

Effect of a red to far red light filtering plastic film on growth of gardenia (Gardenia jasminoides)

The aim of this study was to determine the influence of a light filtering plastic film (red to far red ratio modification) on gardenia (Gardenia jasminoides) growth and to investigate the possibility to use this film as a greenhouse cover material for compact gardenia pot plant production in a greenhouse. Experiments were carried out on gardenia cuttings and plants grown under low tunnels covered by a) a light filtering (light modification within the range of 600 to 750 nm) plastic film, b) a plastic film with low radiation transmission or c) a common plastic film. The energy flux entering the low tunnels, within the range of 400 to1100 nm, and the climate parameters, along with plant growth parameters (shoot length, leaf area, number of lateral shoots, number of nodes, leaf and root dry weight) were measured. Cuttings rooted under the light filtering plastic film, receiving light with high R/FR and B/R ratio, were found 68% shorter, and had 21% and 29% lower leaf area and dry weight, respectively, compared to cuttings grown under common plastic film. Developed plants grown under the light filtering plastic film were found 59% shorter, produced no lateral shoots, and had lower leaf area, dry weight and node number compared to plants grown under common covering material. So, light filtering plastic films with high R/FR and B/R ratio, could be promising for greenhouse covering, as an alternative method to chemical growth regulator use, for compact gardenia pot plant production. The effect on lateral branching though, may become a serious problem to the final compact plant formation. For this reason photoselective plastic films with different R/FR and B/R ratios must be tested

Effect of irrigation frequency on rose flower production and quality

A better understanding of the effects of irrigation frequency on flower production and quality of rose plants can help to propose optimal irrigation scheduling. For this purpose, experiments were conducted on a soilless rose crop (Rosa hybrida, cv. First Red), with a closed hydroponic system, in a greenhouse located near Volos, on the continental area of eastern Greece. The plants were grown following the bending technique, on rockwool slabs. Irrigation scheduling was based on crop transpiration, and irrigation was performed whenever accumulative solar radiation outside the greenhouse reached 1600 kJ m -2 [high irrigation frequency (HIF)] and 3200 kJ m-2 (low irrigation frequency). The amount of water applied was 0·2 and 0·4 mm for high and low irrigation frequencies, respectively. Accordingly, the total water applied was equal for both cases. In order to study the effects of irrigation frequency on rose crop, measurements of fresh and dry weight of the cut flower shoots, number of harvested flowers and flowering stem's length, as well as measurements of microclimate variables were carried out. The total period of measurements ended 100 days after the last severe shoot bending (which was performed 60 days after planting). The results showed that irrigation frequency influenced cut flower fresh and dry weight, since the total fresh and dry weight of cut flower shoots measured at the end of the experimental period was about 33% higher in the HIF treatment. Statistical analysis revealed that there was no significant difference between the mean fresh or dry weight of cut flower shoots of the two treatments. As far as the number of shoots harvested is concerned, the results showed that the higher the irrigation frequency, the higher the production, as the total number of cut flowers measured at the end of the experimental period was 20·7 and 16·2 per greenhouse m -2 for high and low irrigation frequencies, respectively, namely about 28% higher in the HIF. Furthermore, the results showed that the length of rose flowering shoots was not affected by the irrigation frequency. In conclusion, it seems that the higher irrigation frequency improved the biomass production but did not affect the quality of harvested flowers. © 2005 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd

Effect of two irrigation frequencies on rose flower production and quality

A better understanding of the effects of irrigation frequency on flower production and quality of rose plants can help to develop optimal irrigation systems. On this purpose experiments were conducted on a soilless rose crop (Rosa hybrida, cv. First Red) grown in a closed hydroponic system, in a greenhouse located on Eastern Greece. In order to study the effect of high and low irrigation frequency on rose crop flower production and quality, measurements of cut-flower fresh and dry weight, number of harvested flowers and flowering stem length, as well as measurements of microclimate variables were carried out. Irrigation scheduling was based on crop transpiration and irrigation was performed whenever accumulative solar radiation outside the greenhouse reached 470 kJ m-2 (high irrigation frequency) or 940 kJ m-2 (low irrigation frequency). The amount of water applied was 0.2 mm and 0.4 mm for high and low irrigation frequency, respectively. The results showed that irrigation frequency affected cut flower fresh and dry weight since the total values of cut flower fresh and dry weight measured at the end of the experimental period were 413 and 310 g m-2 for high and 120 and 89 g m-2 for low irrigation frequency, respectively. As far as the number of cut flowers is concerned, the results showed that the higher the irrigation frequency, the higher the production, since the total number of cut flowers measured at the end of the experimental period was 20.7 and 16.2 flowers per greenhouse m-2 for high and low irrigation frequencies, respectively. Finally, the results showed that the quality of rose flowering shoots was not affected by the irrigation frequency. In conclusion, it seems that the higher irrigation frequency improved the biomass production but did not affect the quality of harvested flowers