Paederia foetida L. belonging to family Rubiaceae, is an important medicinal and perennial vine. It has a distinguishing foetid smell due to the presence of methyl mercaptan in its leaves and stems (Bose et al. 1953; Chopra et al. 1969). In India, different tribes use this plant for treating various ailments related to gastral intestine such as stomachache, gastromegaly, flatulence, ulcers, and piles (Chanda et al. 2013; Kumar et al. 2014). The plant was also reported to have anti-inflammatory, anti-cancer, antidiarrheal, antioxidant, antibacterial and antifungal properties (Begum et al. 2007; Osman et al. 2009; Chanda et al. 2013; Kumar et al. 2014). The plant is component of a number of Ayurvedic products available in the Indian market. It is also widely used as a food in different states of India including Odisha, West Bengal and Arunachal Pradesh (Behera et al. 2017).

Unfortunately, P. foetida is enlisted as a vulnerable plant in some states of India including Odisha due to overexploitation by anthropogenic activities (e.g., deforestation, unsustainable harvesting by local baidyas, habitat fragmentation and urbanization) (Srivastava and Srivastava 2004; Ved et al. 2008). The proliferation rate of P. foetida by conventional methods of propagation (i.e., stem cuttings and seeds) is very slow and not enough to meet the commercial demand (Aquilar 2001). The above-mentioned problems necessitate the development of in vitro propagation of P. foetida.

Production of synthetic (or artificial seeds) by encapsulation technology offers incredible potential for in vitro propagation of threatened and commercially valuable plants. Synthetic seed technology has, in fact, combined the advantages of clonal propagation and storage which helps in conservation of germplasm of elite plant species, short- and long-term storage. Besides, due to easy handling and small size of such seeds the exchange of axenic plant material between laboratories is always a possibility (Naik and Chand 2006; Gantait et al. 2015; Gantait et al. 2017a; Qahtan et al. 2019). During last two decades, development of synthetic seeds protocol has been intensified for the production of large number of fruit trees, medicinal and ornamental plant species such as Punica granatum (Naik and Chand 2006), Drimiopsis kirkii (Haque and Ghosh 2014), Rauvolfia serpentina (Gantait et al. 2017a), Plumbago zeylanica (Jain et al. 2018) and Hedychium coronarium (Behera et al. 2020) etc.

In P. foetida, synthetic seed production has not yet been reported. Hence, to the best of our knowledge, the present study is the first report on production of synthetic seed of P. foetida by using in vitro regenerated nodal segments. Low temperature storage and subsequent plant retrieval from the encapsulated nodal segments were also studied so that the techniques will be useful for short term storage and transfer of P. foetida germplasm to different places as per the requirement.

Explant source

The axenic nodal segments (approximately 0.8~1.0 cm) excised from in vitro established shoot cultures of P. foetida on Murashige and Skoog’s (1962) (MS) medium + 3.0 mg/l N⁶-benzylaminopurine (BAP) using nodal explants (Behera et al. 2018) were used as explants for encapsulation.

Encapsulation matrix

Sodium alginate (Hi-media, India) solutions were prepared in five different concentrations i.e., 1, 2, 3, 4 and 5% using liquid MS medium supplemented with 3.0 mg/l BAP (Himedia, India). For complexation calcium chloride (CaCl₂) at three different concentrations i.e., 75, 100, 125 mM was prepared in liquid MS medium supplemented with 3.0 mg/l BAP. The pH of both sodium alginate and CaCl₂ was adjusted to 5.8 ± 0.1 prior to autoclave at 121°C and 15 pounds per square inch pressure for 17 min.

Encapsulation of axenic nodal segments and effect of encapsulation matrix on sprouting of synthetic seeds

Axenic nodal segments were immersed in sodium alginate solution (1~5%). Drops of sodium alginate solution containing the nodal segment was allowed to fall on CaCl₂ (75~125 mM) solution using a glass pipette and kept for 20 min for ion exchange. The beads, each with a single axenic nodal segment, were collected by pouring out the CaCl₂ solution. The beads were washed three times with autoclaved double distilled water and placed on sterilized tissue paper to remove excess water. The encapsulated nodes are now called as synthetic seeds and ready for further experiments. To examine the sprouting frequency of synthetic seeds, they were cultured/ inoculated on plant growth regulator free ½ MS medium. Data were recorded regarding the percentage of sprouting at day 14 of culture.

Evaluation of culture media and auxins on sprouting and/or germination of synthetic seeds

For experimentation on sprouting [production of only shoot(s)] and germination [production of both shoot(s) and root(s) on the same medium], the axenic nodal segments were encapsulated with best encapsulation matrix i.e., sodium alginate (3%) + CaCl₂ (100 mM) with a complexation time of 20 min. To adjust the optimum strength of MS basal media as substrate for germination, the synthetic seeds were inoculated on various strengths of MS media (i.e., MS, ½ MS, ¼ MS, 1/8 MS, and 1/16 MS) devoid of any plant growth regulators. Percentage of sprouting and germination was recorded after 14 and 30 days of culture, respectively.

Among the above mentioned five different media substrates tested, the best one (i.e., ½MS; on which maximum response was recorded) was fortified with different auxins at two different concentrations such as indole-3-acetic acid (IAA; 0.5 and 1.0 mg/l) or indole-3-butyric acid (IBA; 0.5 and 1.0 mg/l) or naphthaleneacetic acid (NAA; 0.5 and 1.0 mg/l), to check the influence of auxins for germination of synthetic seeds. All the media used for sprouting and germination were fortified with 30 g/l of sucrose as carbon source with 0.7% agar for solidification.

Influence of low temperature storage on germination frequency of synthetic seeds

For the study on the effect of low temperature storage on germination frequency of synthetic seeds, encapsulation of the axenic nodal explants was done with best combination of sodium alginate (3%) and CaCl₂ (100 mM), with a complexation time of 20 min. Synthetic seeds were then kept in petri-dishes, wrapped with parafilm (Bemis, USA) and stored at 4°C in a refrigerator for different time duration i.e., 7, 15, 21 and 30 days. After each storage period the synthetic seeds were transferred to culture vessels containing ½ MS + 0.5 mg/l IAA and were evaluated for their germination frequency after 30 days.

Rooting of shoots sprouted from synthetic seeds

For those synthetic seeds which failed to germinate into plantlets, another set of experiment was carried out for root induction from the shoots obtained from the sprouted synthetic seeds. The regenerated shoots obtained from such synthetic seeds were transferred to the plant growth regulator free half-strength MS medium for rooting.

Culture conditions

All the cultures for synthetic seed experiments were maintained in a culture room at 25 ± 1°C under 16 h of photoperiod. The light was provided by cool white fluorescent tubes (50 µmol m^-2 s^-1 photon flux density).

Acclimatization and transfer of plants to soil

Well developed plantlets derived from germinated synthetic seeds as well as from rooting experiment were removed from culture medium, washed in tap water to remove traces of calcium alginate and/or agar, and transferred to Styrofoam cups (7.5 cm dia.) having autoclaved soil and sand in the ratio of 1:1 (w/v) as potting mixture. The plantlets were acclimatized following the procedure as described by Behera et al. (2018).

Statistical analysis

For synthetic seed protocol, five conical flasks each containing four synthetic seeds were used. For rooting, ten tubes containing one explant each were taken into consideration. All these experiments were repeated thrice. Observations were recorded at regular interval. The data analysis was carried out using ANOVA. Means with significant effect at P ≤ 0.05 were designated by using DMRT (Duncan’s New Multiple Range Test; Gomez and Gomez 1984).

Effect of encapsulation matrix on sprouting of synthetic seeds

The sprouting ability of the synthetic seeds (Fig. 1A, B) produced by using different combinations of sodium alginate (1, 2, 3, 4 and 5%) and CaCl₂ (75, 100 and 125 mM) was assessed by culturing them on ½ MS medium. The combination of 3% sodium alginate and 100 mM CaCl₂ produced ideal synthetic seeds and showed best results with a maximum sprouting frequency of 100% on ½ MS, after 14 days of culture (Table 1; Fig. 1C-F). When 2% and 4% sodium alginate were used with optimum concentrations of CaCl₂ (100 mM) the rate of sprouting of synthetic seed was 86.7% and 88.3% respectively, which was less than 3% sodium alginate.

Table 1 . Effects of sodium alginate and CaCl₂ concentrations (with a 20-min complexation time) on the sprouting of synthetic seeds (encapsulated axenic nodal segments) of Paederia foetida on ½ MS after 14 days of culture.

CaCl2 (mM)	Sodium alginate (%; w/v)	Sprouting of synthetic seeds (%)
75	1	21.7jk
	2	46.7gh
	3	68.3de
	4	66.7def
	5	58.3efg
100	1	43.3hi
	2	86.7abc
	3	100a
	4	88.3ab
	5	66.7def
125	1	33.3hij
	2	58.3efg
	3	75.0bcd
	4	46.7gh
	5	16.7kl

Values within a column followed by same letters are not significantly different (P ≤ 0.05; DMRT).

Figure 1. (A) In vitro multiple shoots (on MS + 3.0 mg/L BAP) that were the source of axenic nodal segments for encapsulation and preparation of synthetic seeds. (B) Excised axenic nodal segments from the primary shoots ready for encapsulation. (C) Production of synthetic seeds by encapsulation of axenic nodal segments using sodium alginate (3%) and CaCl₂ (100 mM) with 20 min of ion exchange. (D) Synthetic seeds cultured on ½ MS medium. (E) Sprouting of the synthetic seeds on ½ MS medium. (F) Enlarged view of a sprouted synthetic seed. (G) Germination of synthetic seeds on ½ MS medium (roots indicated by arrow). (H) Magnified view of a single germinated synthetic seed after 14 days of culture. (I) Germinated synthetic seed showing emergence of roots and shoots on ½ MS + 0.5 mg/L IAA after 30 days of culture. (J) Acclimatized plants in pots containing garden soil

Higher concentration(s) of sodium alginate and CaCl₂ combinations i.e., 4% sodium alginate with 125 mM CaCl₂ and 5% sodium alginate with 125 mM CaCl₂ were not found to be suitable for production of synthetic seeds as the sprouting ability of these combinations were quite low i.e., 46.7% and 16.7%, respectively. Synthetic seeds prepared using lower concentration of sodium alginate i.e., 1% or 2% and CaCl₂ (75 mM) failed to show good sprouting on ½ MS medium (Table 1). Similarly, combination of 1% or 2% sodium alginate and 125 mM CaCl₂, produced synthetic seeds which exhibited poor sprouting response i.e., 33.3% and 58.3%, respectively. Lower concentration of sodium alginate (1%) in combination with 100 mM CaCl₂ was also unsuitable and only 43.3% sprouting of synthetic seeds was observed (Table 1). Among all the combinations of sodium alginate and CaCl₂ tested for sprouting of synthetic seeds, least percentage (16.7%) of sprouting was recorded when they were prepared using highest percent of sodium alginate (5%) and CaCl₂ (125 mM).

Evaluation of culture media and auxins on sprouting and/or germination of synthetic seeds

The sprouting and germination frequency of the synthetic seeds, prepared in sodium alginate (3%) and CaCl₂ (100 mM), varied with different strengths (MS, ½ MS, ¼ MS, ⅛ MS, 1/16 MS) of media used for culture (Table 2). Out of different strengths of MS media tested, ½ MS was found to be the most suitable medium for sprouting as well as germination of synthetic seeds, where 100% sprouting and 53.3% germination was recorded in 14 days and 30 days, respectively (Table 2; Fig. 1G-H). On this medium the sprouting of synthetic seeds started within 3~4 days of culture. Further reduction of strength of medium beyond ½ MS reduced the frequency of sprouting and germination of synthetic seeds. Among all the media tested, least percentage of sprouting (38.3%) was recorded on 1/16 MS. On this medium the synthetic seeds also failed to show any germination (Table 2).

Table 2 . Effect of media substrates on the sprouting and germination of synthetic seeds (prepared by encapsulating an axenic nodal segment with 3% sodium alginate and 100 mM CaCl₂) of Paederia foetida after 30 days of culture.

Media substrate	Sprouting (%)	Germination (%)
MS	83.3b	46.7ab
½ MS	100a	53.3a
¼ MS	75.0bc	40.0bc
⅛ MS	58.3d	31.7d
⅟16 MS	38.3e	0.0e

Values within a column followed by same letters are not significantly different (P ≤ 0.05; DMRT).

The germination frequency of synthetic seeds was quite low (53.3%) on ½ MS as all the seeds unable to produce roots on the above medium at day 30 of culture. Further to test the influence of auxins on germination if any, synthetic seeds were inoculated on ½ MS augmented with various concentrations (0.5~1.0 mg/l) of auxins (IAA, IBA or NAA). The percentage of germination varied with various types and concentrations of auxins tested (Table 3). After 30 days of culture, ½ MS medium fortified with IAA (0.5 mg/l) was found to be best, with highest germination percentage (83.3%) of the synthetic seeds. The average number of shoots and roots per synthetic seed were 3 and 9, respectively (Fig. 1I). The average shoot and root length was recorded to be 4.5 cm and 3.8 cm, respectively. Half-strength MS medium when supplemented with IBA (0.5 mg/l or 1.0 mg/l) showed 25% germination of synthetic seeds, after 30 days of culture. The synthetic seeds cultured on these media showed shoot regeneration with abnormal rooting accompanied by callus formation (Table 3). However, the number of shoots produced was comparatively more in lower concentration (0.5 mg/l) of IBA. The synthetic seeds failed to germinate or even sprout on ½ MS medium supplemented with NAA, as callusing was seen on the explants within synthetic seeds (Table 3).

Table 3 . Influence of auxins on the sprouting and germination of synthetic seeds of Paederia foetida after 30 days of culture.

Media substrate	Sprouting (%)	Germination (%)	Shoot/ synthetic seed	Shoot length (cm)	Root/ synthetic seed	Root length (cm)
½ MS	100a	53.3c	3.0a	3.3abc	7.0bc	2.5bc
½ MS + IBA 0.5 mg/l	25.0c*	25.0d*	2.0ab	2.8bcd	**	**
½ MS + IBA 1.0 mg/l	25.0c*	25.0d*	1.0bc	1.0e	**	**
½ MS + NAA 0.5 mg/l	C	C	-	-	-	-
½ MS + NAA 1.0 mg/l	C	C	-	-	-	-
½ MS + IAA 0.5 mg/l	100a	83.3a	3.0a	4.5a	9.0a	3.8a
½ MS + IAA 1.0 mg/l	86.7ab	68.3b	1.0bc	4.0ab	7.9ab	2.8ab

C, Callusing; *, sprouting/conversion with callus; **, abnormal root with callus. Values within a column followed by same letters are not significantly different (P ≤ 0.05; DMRT)..

Effect of low temperature storage on germination frequency of synthetic seeds

Variation in the duration (7, 15, 21 and 30 days) of storage of synthetic seeds (at 4°C) influences both germination and regeneration frequency (Table 4). The germination frequency of the synthetic seeds after 7 days of storage was found to be at par with the freshly prepared synthetic seeds on ½ MS supplemented with 0.5 mg/l IAA. The synthetic seeds were stored for a period of 14 days without significant decrease in their germination efficiency (Table 4). It was observed that with an increase in storage time, the percentage of germination of synthetic seeds gradually goes on declining. Thus, the percentage of germination of synthetic seeds declined gradually with the increase in storage time. After 21 and 30 days of storage the germination rate of the synthetic seeds was about 63.3% and 40.0%, respectively.

Table 4 . Germination of synthetic seeds of Paederia foetida after storage at 4°C for different durations.

Storage (days)	Germination (%)	Shoots/ synthetic seed	Shoot length (cm)	Roots/ synthetic seed	Root length (cm)
0	83.3a	3.0a	4.5a	9.0a	3.8ab
7	83.3a	2.8ab	4.3ab	9.0a	3.9a
14	73.3b	2.0c	4.2abc	8.9ab	3.8ab
21	63.3c	2.0c	3.9abcd	7.6c	3.2c
30	40.0d	1.3cd	3.5e	5.2d	3.0d

Values within a column followed by same letters are not significantly different (P ≤ 0.05; DMRT).

Rooting of shoots sprouted from synthetic seeds

Half-strength MS medium was observed to be best for rooting (90%) of shoots excised from sprouted synthetic seeds, which failed to germinate into plantlets. From each shoot an average of 17.8 roots with 2.6 cm length were obtained.

Acclimatization of plantlets

The plantlets obtained from germinated synthetic seeds, after removing traces of agar and alginate were transferred to small Styrofoam cups containing equal proportion (1:1) of autoclaved garden soil and sand where about 86.7% of plantlets were acclimatized. Zero percent mortality was recorded when they were subsequently transferred to larger pots containing soil and then to field conditions. The plantlets regenerated from rooting of sprouted shoots also showed similar trend in acclimatization and successfully transferred to field.

Production of synthetic seeds by alginate encapsulation of somatic embryos or vegetative propagules such as nodal segment or shoot bud provides combined advantages of rapid multiplication of plants with that of storage for germplasm conservation (Standardi and Piccioni 1998, Ara et al. 2000; Srivastava et al. 2009). Ease in handling and transportation of germplasm to other laboratory due to small size of capsules, cost reduction and genetic uniformity of plants are some of the other advantages of synthetic seed technology (Ara et al. 2000; Naik and Chand 2006; Rai et al. 2009; Verma et al. 2015).

Synthetic seeds do not contain nutritive tissue like endosperm, thus preparation of sodium alginate and CaCl₂ without nutrients and/or plant growth regulators may cause a relatively low rate of sprouting and/ or germination (Verma et al. 2010). Amalgamation of nutrients as well as plant growth regulators in the alginate beads can fulfil the role of endosperm for encapsulated explant (Verma et al. 2010). Accessibility of nutrients to the encapsulated explants plays a key factor for germination of synthetic seeds (Fujii et al. 1987; Gantait et al. 2017a) and exogenous application of essential nutrients to serve the role of endosperm is necessary to improve the frequency of germination (Gantait et al. 2017a). Thus, in the present study sodium alginate and CaCl₂ were prepared using MS medium supplemented with 3.0 mg/l BAP. MS + 3.0 mg/l BAP has already been found as optimal medium for axillary shoot proliferation of axenic nodal segments and was the basis of opting the same for preparation of synthetic seed. Preparation of sodium alginate along with appropriate basal medium with or without plant growth regulator (to act as artificial endosperm) has also been reported in different plants such as Bacopa monnieri (Rency et al. 2017), and Salvia officinalis (Grzegorczyk and Wysokiska 2011).

In recent years, the use of non-embryogenic vegetative propagules like nodal segments, axillary buds, apical shoot buds, protocorm like bodies etc., as an alternative to somatic embryos for encapsulation and production of synthetic seeds has also been reported in a number of plant species (Gantait et al. 2015). Plants in which either somatic embryogenesis is not reported or production of uniform quality of embryos is lacking, the only alternative is to use the non-embryogenic vegetative propagules (Rai et al. 2009). Incidentally, somatic embryogenesis is yet to be reported in P. foetida. At the same time use of nodal segments for axillary shoot proliferation has been by far the safest method for micropropagation, as it does not usually induce somaclonal variation. For the reasons mentioned above, in this study the axenic nodal segments obtained from shoots culture established on MS + 3.0 mg/l BAP were selected as the explants for synthetic seed production. Use of axenic nodal segments for successful production of synthetic seeds was well documented in a number of medicinal plant species like Eclipta alba (Singh et al. 2010), Ruta graveolens (Ahmad et al. 2012), Tylophora indica (Gantait et al. 2017b), Vitex trifolia (Alatar et al. 2017) and Withania somnifera (Fatima et al. 2013).

The concentration of sodium alginate and CaCl₂ affect the sprouting as well as germination ability of the synthetic seed. In the present report, highest percentage of sprouting (100%) was reported in the synthetic seeds which were produced using sodium alginate (3%) and CaCl₂ (100 mM). Similar reports of highest frequency of sprouting and/ or germination of synthetic seed using 3% sodium alginate and 100 mM CaCl₂ has also been reported in many medicinal plants including Artocarpus lakoocha (Verma et al. 2015), Vitex trifolia (Alatar et al. 2017). Synthetic seeds prepared with higher concentrations of sodium alginate i.e., 4% or 5% as well as CaCl₂ (125 mM) resulted in suppression of sprouting ability of the synthetic seeds which may be either due to the hardness of the bead which inhibit the emergence of the shoots (Khan et al. 2013) or may be due to CaCl₂ toxicity (Gantait et al. 2015). As discussed earlier, optimal ion exchange of Na⁺ and Ca²⁺ controls the hardness of the beads of the synthetic seeds which in turns influence its sprouting and/ or germination. The optimum concentrations of sodium alginate and CaCl₂ for maximum sprouting and/ or germinations of synthetic seeds vary from propagules type and plant species (Perveen and Anis 2014). Contrary to our finding 4% sodium alginate with 100 mM CaCl₂ was reported as the best combination for preparation and utilization of synthetic seeds in medicinal plants including Clitoria ternatea (Kumar and Thomas 2012), Ficus carica (Sharma et al. 2015), and Zingiber officinale (Sundararaj et al. 2010). Such difference in the required concentrations of sodium alginate for production and utilization of synthetic seed was may be due to variation in purity level of commercial source from which the chemicals were procured (Redenbaugh et al. 1986; Pattnaik and Chand 2000; Sharma et al. 2015; Rathore and Kheni 2017).

Next part of experimentation on development of synthetic seed technology was evaluation of different culture media substrate (i.e., various concentrations of MS basal media like 1/16 MS, 1/8 MS, ¼ MS, ½ MS and MS) for sprouting and germination of synthetic seeds. Different strengths of MS basal media showed varied responses to sprouting and/ or germination of synthetic seeds. Half-strength MS media was recorded to have better results (sprouting, 100% and subsequent germination, 53.33%) in comparison to other strengths of MS media tested. The reason for less responsiveness of other strengths of MS was probably due to their nutrient toxicity or deficiency (Gantait et al. 2017a). Germination of synthetic seeds were enhanced and best conversion rate (83.3%) was recorded when ½ MS was augmented with 0.5 mg/l IAA. Addition of auxin to the sprouting/ germination medium was also found necessary in some medicinal plant species including Glycyrrhiza glabra (IAA; Mehrotra et al. 2012) and Salvia officinalis (IAA; Grzegorczyk and Wysokiska 2011) for better germination of synthetic seeds prepared from different vegetative propagules. In this study supplementation of IBA and NAA with ½ MS failed to enhance the germination frequency, rather detrimental, indicating the use of auxin for such response is species specific.

One of the desirable characters of synthetic seed is their ability to retain viability (i.e., the sprouting and germination potential) even after a considerable period of storage. This feature is necessary for their use in germplasm distribution and exchange (Ahmad et al. 2012; Jahan and Anis 2015). Low temperature and proper moisture were necessary during storage for maintenance of viability of synthetic seeds (Hegazi 2011). In this study, storage duration (7, 15, 21 and 30 days) was found to influence the frequency of germination of synthetic seeds stored at 4°C. The viability of synthetic seeds goes on decreasing with increased duration of storage of synthetic seeds. This type of decreased viability in stored synthetic seeds was might be because of inhibition of tissue respiration due to the presence of alginate (Redenbaugh et al. 1987; Naik and Chand 2006; Hegazi 2011) or loss of moisture during storage (Danso and Ford-Lloyd 2003; Fatima et al. 2013). Similar type of observation of decrease in viability after storage of synthetic seeds was also recorded in various medicinal plants like Capparis orientalis (Hegazi 2011), Eclipta alba (Singh et al. 2010) and Ficus carica (Sharma et al. 2015).

In the present study, the shoots generated from sprouted synthetic seeds (those who failed to germinate) were rooted successfully on plant growth regulator free ½ MS. Similar observation of rooting were also reported in Albizia lebbeck (Perveen and Anis 2014), Bacopa monnieri (Rency et al. 2017), Cassia angustifolia (Bukhari et al. 2014), Cineraria maritime (Srivastava et al. 2009), Nyctanthes arbortrisits (Jahan and Anis 2015), Ruta graveolens (Ahmad et al. 2012) and Withania somnifera (Fatima et al. 2013). Acclimatization of in vitro raised plants is always considered as a critical stage due to possibilities of high percentages of plant loss during transplantation (Pospóšilová et al. 1999; Ahmad et al. 2012). The plantlets obtained after germination of synthetic seeds have been successfully acclimatized in field conditions.

The synthetic seed system using encapsulation of axenic nodal segments of P. foetida has been reported here. In recent years, such synthetic seeds system has been employed in a number of medicinal plant species and established as a fitting alternative for clonal propagation, conservation and germplasm distribution and exchange (Ahmad et al. 2012, Fatima et al. 2013, Gantait et al. 2015). P. foetida plants regenerated through axillary shoot proliferation of axenic nodal segments usually produced clonal plant. Since in this study axenic nodal segments have been used for encapsulation, the plants produced from this system are expected to be clonal. Retrieval of P. foetida plants following storage at low temperature (4°C) implies the potential of the synthetic seed system to be used for germplasm distribution and exchange without losing its viability during transportation. At the same time the developed synthetic system could be useful for short term storage of this threatened plant species and form the basis of further research for developing long- term conservation methods using cryopreservation.

BB gratefully acknowledge the RGNF funding of UGC. The grant of DST, Government of India under DST-FIST programme to the Department of Botany is gratefully acknowledged.