Florists’ greens are a very important element of floral compositions, and their vase life must match that of the flowers. Florists’ greens include foliage, the leafy and non-leafy stems of herbaceous plants, trees, bushes, and phylloclades. The post-harvest longevity of florists’ greens is influenced by genetics. Also strongly affected by the growing conditions and the conditions of the transport of the florists’ greens and the conditions when supplying them to markets are also significant. Moreover, florists’ greens are not supplied with growth regulators, which play a critical role in their ageing process. The cytokinins (CKs) and gobberellins (GAs) are considered to be inhibitors of ageing; however, unfortunately, their content in plant tissues decreases during the progressive ageing process, while the amount of regulators that accelerate ageing increases. This review presents the results of research that has been conducted over the years in order to improve the post-harvest longevity of species that are grown for florists’ greens using growth regulators from the groups of GAs and CKs.
1. Introduction
‘Florists’ greens’ is a conventional term that describes all of the bouquet additions that are used in modern floristry. Florists’ greens include foliage, the leafy and non-leafy stems of herbaceous plants, trees, bushes, and phylloclades. It is often the case that florists’ greens extend to the fruiting and flowering shoots that end in inflorescences consisting of small flowers
[1][2][3]. The commercially available florists’ greens include species that are grown under cover, such as in greenhouses and polytunnels, for cut flowers and as potted plants for indoor decoration. Annual and perennial outdoor plants are also frequently grown because their cultivation cost is much lower
[1][2][3][4]. The post-harvest longevity of florists’ greens is influenced by genetics
[1]. Of the species that are grown in greenhouses, those with leathery, succulent, or waxy cuticle-covered leaves are particularly durable, such as those that are found in the following species:
Anthurium cultorum,
Zantedeschia sp.,
Hippeastrum sp.,
Spatiphyllum sp.,
Monstera deliciosa,
Philodendron selloum, and
Syngonium podophyllum. The species with colorful leaves, including
Cordyline terminalis and
C. fruticosa, are becoming increasingly important in this regard. Phylloclades are particularly durable. They have modified lateral shoots that resemble the structure of true leaves and perform their functions, such as those that are found in
Ruscus sp. and
Asparagus sp. In a dry environment, they are less likely to lose water through transpiration, and it is this negative water balance that is created by the loss of moisture from the leaf blades, or by the blockage of the conducting vessels preventing water uptake, that is the most important reason for the ageing of florists’ greens
[5][6][7]. Among garden perennials, the leaves of
Hosta sp.,
Heuchera sp.,
Bergenia cordifolia,
Paeonia sp.,
Stachys lanata,
Vinca major,
Pulmonaria saccharata,
Dictamnus albus, and
Astilbe x
arendsii stand out for their good longevity. When it comes to annual plants,
Molucella laevis and
Bupleurum griffithii are widely cultivated. In the case of these species, entire shoots are used
[7].
Yellowing, drooping, wilting, or withering leads to the loss of the ornamental value of the florists’ greens, which have great variation among species and cultivars in terms of the post-harvest longevity, the resistance to transport conditions, and the storability
[6][8]. Florists’ greens are divided into three groups based on their storability
[6]. The first group includes fern species of the
Cyrtomium,
Polystichum, and
Anturium cultorum genera
[6][9], as well as
Ruscus [6][10], which can be stored more than 3 weeks. The second group covers species of the
Asparagus and
Pteris cretica genera, which can be stored for 2–3 weeks. The last group includes species that can be stored for 10–14 days, such as
Asparagus virigatus, as well as
Nepfrolepis exaltata, and its cultivars
[6].
The post-harvest longevity of florists’ greens is strongly affected by the growing conditions—the more they match the requirements of each species, the better the longevity will be
[5]. The conditions of transporting florists’ greens and the conditions when supplying them to markets are also significant. Dry transport exacerbates the water stress that is initiated when the leaves and the leafy shoots are cut from the parent plants
[1]. Moreover, florists’ greens are not supplied with growth regulators, which play a critical role in their ageing process
[5][6]. Cytokinins (CKs) and gibberellins (GAs) are considered to be ageing inhibitors; however, unfortunately, their content in the plant tissues decreases during the progressive ageing process, while the levels of the regulators that accelerate the ageing process—ethylene, salicylic acid (SA), brassinosteroids (BR), abscisic acid (ABA), and jasmonic acid (JA)—increase
[11]. In ageing leaf cells, membrane-damaging enzymes become active
[2], proteolysis
[12][13] and the breakdown of chlorophyll accelerates
[1][6][10], and free radicals are produced in large quantities in the cells, destroying the cell components
[14]. The production of reactive oxygen species (ROS) is one of the earliest responses of plant cells to ageing
[15][16]. The ROS are formed as by-products of the aerobic energy metabolism, as well as from plant exposure to various biotic and abiotic stresses
[17][18][19]. Under normal conditions, the ROS production in cells is kept low by the antioxidant enzymes. This balance can be disrupted by antioxidant depletion or the excessive accumulation of ROS, leading to oxidative stress, and resulting in damage to cellular macromolecules and membranes, as well as increased lipid peroxidation
[20][21]. One of the most important ROS is hydrogen peroxide (H
2O
2), due to its relative stability and its ability to diffuse through membranes. H
2O
2 plays an important role during ageing, as it is a signal molecule of the ageing process. Its accumulation is indicative of oxidative stress
[22].
A decrease in the chlorophyll content is the first visual symptom of leaf ageing
[23][24]. The accompanying degradation of proteins, due to the increased proteolytic enzyme activity
[25], results in the accumulation of ammonium and free amino acids, including free proline, which maintains the osmotic balance between the cytoplasm and the vacuole, and affects the protein structure and synthesis
[24][26][27]. Delaying proteolysis is fundamental to slowing down ageing. Specific endo- and exo-proteases hydrolyze the peptide bonds that release the amino acids. The final products of hydrolysis, including ammonia (NH
3), are dangerous to the cells, therefore, they are converted into less toxic forms, such as amides, which are also easier to transport
[28]. The protein and RNA degradation, on the other hand, coincide with the loss of photosynthetic activity, due to chlorophyll breakdown
[23].
2. Harvest and Pre-Treatment of Florists’ Greens
The healthy and undamaged leaves or shoots are cut early in the morning, due to the good tissue turgor pressure
[6][7][8][29][30], or before the evening, due to the accumulation of assimilates in the tissues. It is advisable to cut the fully mature, undamaged leaves. Cutting the young leaves is not advisable, as they do not maintain their ornamental value for long after cutting
[7].
Immediately after harvesting, florists’ greens should be placed into containers with water or should be conditioned and cooled
[6][7][8]. The temperature for cooling, storing, and transporting the florists’ greens is species-dependent. Most of the species of florists’ greens prefer a temperature range of 2–4 °C. However, a temperature of at least 7 °C must be ensured for topical plant species at all of the stages of marketing
[6][7].
The conditioning of the florists’ greens is a treatment that is carried out by the producer of the plants. It prevents water loss from the tissues, protects against the damaging effects of ethylene, inhibits the growth of microorganisms, and prevents the tissues from losing too many reserves
[7][31]. Cooling the leaves of perennials at 4 °C immediately after cutting has, in most cases, a beneficial effect on their longevity in compositions. At the same time, these leaves should be kept in water for at least 12 h in order to ensure their better condition and a longer post-harvest longevity (
Bergenia and
Dictamnus). For outdoor ferns, however, it is better to place the ends of the petioles into boiling water (for up to 10 s)
[7]. The conditioning takes 4–24 h. Short conditioning (4 h) takes place at 18–20 °C, while long conditioning (24 h) is carried out in a freezer at 4–5 °C
[31]. There was an attempt to use a standard cut flower medium containing 2% sucrose and hydroxyquinoline esters—sulphate or citrate (8HQS and 8HQC)—at a concentration of 200 mg·dm
–3 in order to condition the florists’ greens, however it was not shown to have a positive effect on the florists’ greens of most species (
Table 1,
Figure 1)
[3][7][32][33].
Figure 1. Leaves of Zantedeschia elliottiana ‘Black Magic’. (A) control (B) conditioned in GA3 at a concentration of 300 mg dm−3 and stored in 8HQC.
Table 1.
Vase life of florists’ greens after the application of 8HQC + 2% sucrose.
Species |
Vase Life (Days) |
Effect of the Preservative |
Source |
In H2O |
In 8HQC + Sucrose |
Adiantum hispidulum |
15 |
13 |
- |
Skutnik [7] |
Adiantum tenerum |
15 |
3 |
- |
Skutnik [7] |
Areca lutescens |
10 |
13 |
+ |
Skutnik [7] |
Arum italicum |
15.5 |
14.5 (in 8HQS) |
] |
Paeonia lactiflora |
21 |
14 |
- |
Skutnik |
[ |
7 | ] |
Pteris cretica |
13 |
20 |
+ |
Skutnik [7] |
Pulmonaria saccharata |
5 |
4 |
- |
Skutnik [7] |
Zantedeschia aethipica |
17 |
8 |
- |
Skutnik [7] |
Zantedeschia elliottiana‘Florex Gold’ |
10.3 |
6.1 (in 8HQC)/6.2 (in 8HQS) |
- |
Janowska and Jerzy [32] |
3. Growth Regulators and Post-Harvest Longevity of Florists’ Greens
Research into the post-harvest longevity of florists’ greens started quite late, i.e., at the beginning of the last century. It can be linked to the increasing importance of green plant additions in floral compositions. As the ageing process of the florists’ greens is different to that of the flowers, in most cases the same measures that are used for the flowers cannot be used for them
[29][34]. International research is focusing on the use of growth regulators in the post-harvest treatment of florists’ greens. Their effectiveness has been shown to depend on the species, the cultivar, the concentration, and the method of application, therefore, there is no ready-made recipe that can be used for all of the species and all recommendations must be backed up by research. The growth regulators from the group of CKs and GAs are used in order to conditioning the florists’ greens
[1][3][4][6][8][11][29][30][31][32][34][35][36]. The most important GA is gibberellic acid (GA
3). Of the CKs, benzyladenine (BA), which is a synthetic CK, is the most commonly used growth regulator. Few studies to date point to the possibility of using topolines (Ts)
[1][28][37] and ionic liquids
[1][38] in order to extend the post-harvest longevity of florists’ greens (
Table 2).
Table 2.
Growth regulators that are used to extend the vase life of florists’ greens.
Species |
Growth Regulator |
Concentration |
Source |
Alchemilla mollis |
BA |
25 mg·dm−3 |
Janowska et al. [29] |
GA3 |
25 and 50 mg·dm−3 |
MemT and MemTR |
75 mg·dm−3 |
Arum italicum |
GA | 0 |
3 |
100 mg·dm−3 |
Janowska [8], Janowska and Schroeter-Zakrzewska [33Janowska and Schroeter-Zakrzewska [33] |
] |
Asparagus densiflorus ‘Sprengeri’ |
16 |
15 |
0 |
Asparagus densiflorus ‘Myriocladus’ |
GA3 | Skutnik |
0.25 mmol·dm−3 (pulsing) | [ |
Skutnik et al. [39]7] |
Asparagus falcatus |
16 |
25 |
+ |
Skutnik [7] |
|
1 mmol·dm−3(dipping) |
Asparagus setaceus |
38 |
24 |
- |
Skutnik [7] |
BA |
0.1 mmol·dm−3 (pulsing) |
Asparagus virgatus |
25 |
38 |
+ |
Skutnik [ |
|
1 mmol·dm−3(dipping) | 7 | ] |
Cyclamen persicum |
Asparagus falcatus | 41 |
29 |
- |
BA |
0.1 and 1 mmol·dmSkutnik [7] |
−3 |
Skutnik and Rabiza-Świder | [ | 40] |
Eucalyptus cinerei |
15 |
16 |
0 |
Skutnik [7] |
GA3 |
1 mmol·dm−3 |
Hippeastrum × hybridum |
10 |
10 |
0 |
Skutnik [7] |
Asparagus setaceus |
BA |
0.1 mmol·dm−3 (pulsing) |
Skutnik et al. [ |
Hosta plantaginea |
10 |
6 |
- |
Skutnik [7] |
41 | ] |
Hypericum calycinum |
50 |
35 |
- |
Skutnik [7] |
Hypericum inodorum |
1 mmol·dm−3(dipping) |
Asparagus umbellatus |
BA |
50 and 250 mg·dm−3 |
Pogroszewska and Woźniacki [42] |
‘Magical Beauty’ |
11 |
18.8 (conditioning in 8HQS/17.8 (holding solution in 8HQS) |
+ |
Campsi radicans |
GA3 |
500 mg·dm−3 (dipping) |
Pogroszewska and Woźniacki [42] | Janowska and Śmigielska [3] |
Molucella laevis with/without leaves |
20/20 |
10/17 |
BA | |
Skutnik | [ | 7] |
50 mg·dm | −3 (conditioning) |
Nephrolepis cordifolia |
16 |
18 |
0 |
Skutnik [7] |
Cimicifuga racemosa |
GA3 |
500 mg·dm−3 (dipping) |
Pogroszewska and Woźniacki [42] |
N. exaltata |
23 |
22 |
0 |
BA |
250 mg·dm−3 (dipping) | Skutnik | [ | 7 |
Codieum variegatum |
GA3 BA |
250 mg·dm−3 (conditioning) 50 mg·dm−3 (conditioning) 250 mg·dm−3 (dipping) |
Pogroszewska and Woźniacki [42] |
Convallaria majalis |
GA3, [Q-C2][Gib], [Gib][Ach], [Chol][Gib], [Q-C12][Gib] |
50 and 100 mg·dm−3 |
Szymaniak et al. [38] |
Cordyline ‘Glauca’ |
BA, GA3 |
1 mmol·dm−3 |
Koziara and Suda [43] |
Dieffenbachia sp. |
GA3 |
1 mM |
Koziara i Sikora [41] |
Geranium platypetalum |
GA3 |
25 and 50 mg·dm−3 |
Janowska et al. [31] |
Hedera helix |
GA3 BA |
250 mg·dm−3 (conditioning) 500 mg·dm−3 (dipping) 50 mg·dm−3 (conditioning) 250 mg·dm−3 (dipping) |
Pogroszewska and Woźniacki [42] |
Hemerocallis × hybrida ‘Agata’ |
MemT, MemTR [Q-C2][Gib] [Gib][Ach], [Chol][Gib], [Q-C12][Gib] |
50 and 100 mg·dm−3 100 mg·dm−3 50 and 100 mg·dm−3 |
Janowska et al. [1] |
Heuchera hybrida ‘Chocolate Ruffles’ |
BA MemT MemTR |
50 and 100 mg·dm−3 |
Janowska et al. [1] |
×Heucherella ‘Solar Power’ and ‘Kimono’ |
BA |
100, 300, and 600 mg·dm−3 |
Janowska et al. [30] |
Hosta ‘Golden Tiara’, ‘Minima Glauca’ and ‘Crispula’ |
BA GA3 |
0.1 mmol·dm−3 0.25 mmol·dm−3 |
Rabiza-Świder et al. [44] |
Limonium latifolium |
[Gib][Ach] [Q-C12][Gib] GA3, BA, MemT, MemTR |
50 and 100 mg·dm−3 100 mg·dm−3 25, 50, and 75 mg·dm−3 |
Janowska et al. [1] Janowska et al. [37] |
Monstera deliciosa |
GA3 |
25 and 50 mg·dm−3 |
Farahat and Gaber [45] |
Schefflera arboricola |
GA3 BA |
250 mg·dm−3 (conditioning) 500 mg·dm−3 (dipping) 50 mg·dm−3 (conditioning) 250 mg·dm−3 (dipping) |
Pogroszewska and Woźniacki [42] |
Spathiphyllum wallisii |
GA3 BA |
0.25 and 1 mM 0.1 and 1 mM |
Koziara i Sikora [41] |
Spathiphyllum wallisii ‘Castor’ |
GA3 BA |
250 mg·dm−3 (conditioning) 500 mg·dm−3 (dipping) 50 mg·dm−3 (conditioning) 250 mg·dm−3 (dipping) |
Pogroszewska and Woźniacki [42] |
Thalictrum aquilegifolium |
BA |
50 mg·dm−3 (conditioning) 250 mg·dm−3 (dipping) |
Pogroszewska and Woźniacki [42] |
Zantedeschia aethiopica |
BA GA3 |
0.1 mM 0.25 and 1 mM |
Skutnik et al. [34] |
Zantedeschia albomaculata ‘Black Eyed Beauty’ ‘Albomaculata’ |
GA3 Memt, MemTR |
50 and 100 mg·dm−3 25, 50, and 75 mg·dm−3 |
Janowska and Stanecka [35] Janowska et al. [36] |
Zantedeschia elliottiana ‘Florex Gold’ ‘Black Magic’ |
GA3 |
200 and 300 mg·dm−3 100, 200, and 300 mg·dm−3 |
Janowska and Jerzy [32] |
Zantedeschia sp. ‘Sunglow’ |
GA3 |
400 mg·dm−3 |
Janowska and Stanecka [35] |