In vitro clonal propagation of Nyctanthes arbor-tristis

Rapid shoot multiplication of Nyctanthes arbor-tristis L. was achieved from axillary meristems on Murashige and Skoog (MS) basal medium supplemented with 1.0–1.5 mg dm⁻³ 6-benzylaminopurine (BA), 50 mg dm⁻³ adenine sulfate (Ads) and 3 % (m/v) sucrose. Inclusion of indole-3-acetic acid (IAA) in the culture medium along with BA + Ads promoted a higher rate of shoot multiplication. Maximum mean number of microshoots per explant (6.65) was achieved on the MS medium supplemented with 1.5 mg dm⁻³ BA, 50 mg dm⁻³ Ads and 0.1 mg dm⁻³ IAA after 4 weeks of culture. The elongated shoots rooted within 13 to 14 d on half-strength MS medium supplemented with either indole-3-butyric acid (IBA), IAA or 1-naphthaleneacetic acid (NAA) with 2 % sucrose. Maximum percentage of rooting was obtained on medium having 0.25 mg dm⁻³ IBA and 0.1 mg dm⁻³ IAA. About 70 % of the rooted plantlets survived in the greenhouse. The in vitro raised plants were grown normally in the field.     

<Emphasis Type="Italic">In vitro</Emphasis> multiplication of heavy metals hyperaccumulator <Emphasis Type="Italic">Thlaspi caerulescens</Emphasis>

A micropropagation protocol through multiple shoot formation was developed for Thlaspi caerulescens L., one of the most important heavy metals hyperaccumulator plants. In vitro seed-derived young seedlings were used for the initiation of multiple shoots on Murashige and Skoog (MS) medium with combinations of benzylaminopurine (BA; 0.5–1.0 mg dm⁻³), naphthaleneacetic acid (NAA; 0–0.2 mg dm⁻³), gibberellic acid (GA₃; 0–1.0 mg dm⁻³) and riboflavin (0–3.0 mg dm⁻³). The maximum number of shoots was developed on medium containing 1.0 mg dm⁻³ BA and 0.2 mg dm⁻³ NAA. GA₃ (0.5 mg dm⁻³) in combination with BA significantly increased shoot length. In view of shoot numbers, shoot length and further rooting rate, the best combination was 1.0 mg dm⁻³ BA + 0.5 mg dm⁻³ GA₃ + 1.0 mg dm⁻³ riboflavin. Well-developed shoots (35–50 mm) were successfully rooted at approximately 95 % on MS medium containing 20 g dm⁻³ sucrose, 8 g dm⁻³ agar and 1.0 mg dm⁻³ indolebutyric acid. Almost all in vitro plantlets survived when transferred to pots.     

Influence of selected carbohydrates on rhizogenesis of shoots saucer magnolia in vitro

Nodal segements were taken from juvenile shoots of mature 100 year-old trees of saucer magnolia (Magnolia x soulangiana Soul.-Bod.) and cultured on Standardi and Catalano medium supplemented with 1.33 μmol·dm⁻³ BA, 0.54 μmol·dm⁻³ NAA, 58 μmol·dm⁻³ sucrose and 6.0 g·l⁻¹ agar-agar. After 8 weeks, separated shoots were transferred to rooting medium with half-strength macronutrients (basal medium) supplemented with 0.3% activated charcoal and one of carbohydrates: arabinose, cellulose, fructose, galactose, glucose, lactose, mannose, rhamnose, ribose, sorbose, sucrose or xylose at 20 g·dm⁻³ and 7.0 g·dm⁻³ agar-agar. After 13 weeks of culture, shoot number, fresh and dry weight of shoots and roots, total root length and number of roots/per shoot were recorded. Percentages of rooted shoots were calculated. Fructose, mannose and xylose were the most effective carbon source on shoot proliferation followed by sucrose. The rooting response was induced by cellulose and xylose. Arabinose, rhamnose and sorbose inhibited root formation. The number of adventitious roots produced per shoot was stimulated by cellulose and xylose. Total biomass (shoot plus roots) of the plantlets was the highest at fructose and cellulose.     

The effect of phenyl acetic acid on shoot bud induction, elongation and rooting of chickpea

A highly efficient protocol for plant regeneration from cotyledonary node of two chickpea (Cicer arietinum L.) cultivars ICCV-10 and Annigeri used phenylacetic acid (PAA). The Murashige and Skoog (MS) medium supplemented with 2.0 mg dm⁻³ 6-benzylaminopurine (BAP) and 1.0 mg dm⁻³ PAA was used for induction of bud formation. Buds were elongated on MS medium supplemented either with only 0.75 mg dm⁻³ gibberellic acid (GA₃) or 0.2 mg dm⁻³ GA₃ + 0.6 mg dm⁻³ PAA. The elongated shoots were then transferred onto rooting medium containing 1 mg dm⁻³ PAA. The frequency of multiple shoot induction and rooting was higher in Annigeri as compared to ICCV-10. The complete plantlets with well-developed roots were transferred to pots containing sterilized soil and sand in the ratio 3:1 where they survived (74 %) and set normal seeds.     

Extracellular Matrix in Early Stages of Direct Somatic Embryogenesis in Leaves of Drosera spathulata

The growth and water relations of Paulownia fortunei in photoautotrophic cultures (nutrient medium lacking sucrose and growth regulator) with CO₂ enrichment (PWAH) or without CO₂ enrichment (PWAL) were compared with those in photomixotrophic shoot (PWC; 30 g dm⁻³ sucrose and 0.3 mg dm⁻³ N⁶-benzyladenine) and root cultures (PWR; 0.3 mg dm⁻³ indole-3-butyric acid). The photoautotrophic and photomixotrophic cultures were incubated under photosynthetic photon flux 125 and 60 μmol m⁻² s⁻¹, respectively. 100 % sprouting and significantly higher number of shoots (1.6) were obtained with PWAH as compared to PWAL and PWC. PWAH and PWAL stimulated spontaneous rooting from the cut end of axillary shoots. In PWAH, 84 % of shoots rooted with an average of 5.9 roots per shoot and 4.0 cm of root length in 21 d. Rooting of photomixotrophic shoot cultures were stimulated by an auxin treatment. In this case, 98.3 % of shoots were rooted with an average of 4.6 roots per shoot and 1.9 cm length. A microscopic observation on leaf abaxial surface prints from photomixotrophic shoot and root cultures showed widely open (6 – 8 μm) spherical stomata (12 – 14 μm) and from photoautotrophic cultures elliptical stomata (10 – 12 μm) with narrow openings (3 – 4 μm). Leaves from photomixo-trophic cultures had higher stomatal index as compared to photoautotrophic cultures. The rate of moisture loss from detached leaves was not varying significantly in different cultures. This revised version was published online in July 2006 with corrections to the Cover Date.     

In vitro propagation ofBoswellia serrata Roxb

Anin vitro procedure for large scale multiplication ofBoswellia serrata Roxb. has been developed using cotyledonary node segments. In average 4 shoots per node were obtained on Murashige and Skoog's (MS) medium containing 0.5 mg dm⁻³ 6-benzylaminopurine (BAP) and 0.05 mg dm⁻³ napthaleneacetic acid (NAA) within 22 d. By repeated subculture technique 90–100 shoots per node could be obtained after 88 d of initial culture. Shoots could be rooted on MS medium containing 1/4 salts, 1% saccharose, and a combination of 0.5 mg dm⁻³ indole-3-butyric acid (IBA) and 0.25 mg dm⁻³ indole-3-acetic acid (IAA). Addition of antioxidants like polyvinylpyrrolidone (PVP-50 mg dm⁻³) and ascorbic acid (100 mg dm⁻³) in both multiplication and rooting media prevented browning of cultures. Approximately 80% of shoots rooted within 8–10 d. Rooted plantlets were kept for 15 d in culture bottles containing Soilrite^TM irrigated with a nutrient solution containing 1/4 MS salts and finally transferred to pots containing soil: Soilrite^TM (1∶1), mixture with 70% transplantation success.     

In vitro regeneration of Trifolium glomeratum

In vitro regeneration of Trifolium glomeratum, a leguminous forage species, was attempted through leaf, petiole, cotyledon, hypocotyl, collar and root explants and two media combinations. Root and collar explants showed no callus induction. Medium with 0.05 mg dm⁻³ α-naphthaleneacetic acid (NAA) and 0.10 mg dm⁻³ N⁶-benzyladenine (BA) was more effective for hypocotyl explant whereas cotyledon and petiole explant were more responsive to 5.0 mg dm⁻³ NAA and 1.0 mg dm⁻³ BA. Friable, green calli obtained from petiole explant on this medium showed organogenetic potential. Modified root-inducing medium having 0.21 mg dm⁻³ indole-3-acetic acid and 2.5 % sucrose was successful for root induction and plantlets were successfully transferred to field after hardening and Rhizobium inoculation.     

In vitro cultivation of donor quince shoots affects subsequent morphogenesis in leaf explants

The effect of in vitro cultivation of donor shoots on subsequent morphogenesis in leaf explants of quince (Cydonia oblonga Mill.) clone BA29 was investigated. Proliferating donor shoots were cultured in ventilated or closed vessels under different photosynthetic photon flux densities (PPFD; 200 and 100 μmol m⁻² s⁻¹) with 0, 15, 30 g dm⁻³ sucrose. Shoots grown in ventilated vessels, especially with sucrose at 15 or 30 g dm⁻³, were better developed with fully expanded leaves compared to those in standard closed vessels. Leaves collected from pre-treated donor shoots were used to assess regeneration capacity. Somatic embryo production was highest in leaves harvested from shoots cultured in closed vessels with 30 g dm⁻³ sucrose and in ventilated vessels with 15 and 30 g dm⁻³ sucrose and under high PPFD which was, in comparison with the control treatment (closed vessel, 30 g dm⁻³ sucrose and low PPFD), about 2 to 2.5 times higher. A similar response was observed for root regeneration.     

Successful micropropagation protocol of <Emphasis Type="Italic">Piper methysticum</Emphasis>

An efficient in vitro propagation of kava (Piper methysticum) was established. Utilizing 15-d-old tender shoots from dormant auxiliary buds as explants, significant induction of vigorous aseptic cluster shoots was achieved in Murashige and Skoog (MS) medium containing 0.5 mg dm⁻³ 6-benzyladenine (BA), 0.5 mg dm⁻³ indole-3-acetic acid (IAA), and antibiotics after 30 d. In vitro rooting was achieved at 100 % efficiency in MS medium containing 0.75 to 1.00 mg dm⁻³ IAA or indole-3-butyric acid and 3 % sucrose. The most robust and long roots were observed in medium with IBA. Moreover, the embryonic callus was induced from petioles in MS medium supplemented with 1.0 mg dm⁻³ BA and 0.1 mg dm⁻³ IAA, of which 70 % differentiated into shoots in the presence of 1.0 mg dm⁻³ BA and 0.5 mg dm⁻³ IAA.     

<Emphasis Type="Italic">In vitro</Emphasis> minimum growth for conservation of <Emphasis Type="Italic">Drosophyllum lusitanicum</Emphasis>

The present paper reports a protocol for minimum growth conservation of Drosophyllum lusitanicum (L.) Link. in vitro. Double-node cuttings were maintained for 4, 8 and 12 months at 5 or 25 °C in the dark. The effects of sucrose either alone at 5, 20, 30, 40 and 60 g dm⁻³ or at 20, 40 and 60 g dm⁻³ in combination with 20 g dm⁻³ mannitol, on survival and post-storage shoot multiplication efficiency were investigated. The cultures could effectively be conserved under minimum growth at 5 °C for 8 months on Murashige and Skoog’s medium supplemented with 60 g dm⁻³ sucrose, 20 g dm⁻³ mannitol and 0.91 μM zeatin. Following extended conservation, the cultures could be successfully regenerated into new shoots, and they were morphologically similar to those of non-stored controls.     

Somatic embryogenesis and plant regeneration in <Emphasis Type="Italic">Catharanthus roseus</Emphasis>

Embryogenic callus in Catharanthus roseus was initiated from hypocotyl on Murashige and Skoog’s (MS) medium supplemented with 1.0–2.0 mg dm⁻³ of 2,4-dichlorophenoxyacetic acid (2,4-D) or chlorophenoxyacetic acid (CPA). Calli from other sources were non-embryogenic. Numerous somatic embryos were induced from primary callus on MS medium suplemented with naphthalene acetic acid (NAA) within two weeks of culture. Embryo proliferation was much faster on medium supplemented with 6-benzylaminopurine (BAP). After transfer to medium with gibberellic acid (GA₃, 1.0 mg dm^{− 3}) mature green embryos were developed and germinated well into plantlets on MS liquid medium supplemented with 0.5 mg dm⁻³ BAP. Later, embryos with cotyledonary leaves were subjected to different auxins treatments for the development of roots. Before transfer ex vitro, plantlets were cultivated on half strength MS medium containing 3 % sucrose and 0.5 mg dm⁻³ BAP for additional 2 weeks. Additionally, the effect of liquid medium has been evaluated at different morphogenetic stages.     

Direct organogenesis in hop - a prerequisite for an application ofA. tumefaciens-mediated transformation

The regeneration ability of primary explants derived from mericlones of two commercial Bohemian hops was investigated. It was found that these hops are able to regenerate shoots by direct organogenesis on media containing BAP or zeatin at concentrations 0.5–2 mg dm⁻³. The highest regeneration of shoots was achieved from either petioles or internodes at frequencies 21% and 52%, respectively, on the medium containing zeatin (2 mg dm⁻³), while relatively low amount of regenerated shoots (1.3%) was observed for leaf blade explants. On the other hand, more efficient rooting occurred on the leaf blades then on other explants. A similar pattern of regeneration we observed for HLVd-infected mericlones of clone Osvald 31 even though viroid concentration inin vitro cultures was about 8-fold higher than in field-grown plants and was 31.1 pg mg⁻¹ of fresh mass in the average. These results suggest that HLVd infection did not impair organogenesis. We found that high 2,4-D concentration pretreatment (11 mg dm⁻³) did not promote somatic embryogenesis. Although this treatment suppressed direct organogenesis, the inhibition was not complete and in low frequency the shoot regeneration was seen. Sensitivity of hop explants to antibiotics commonly used inAgrobacterium-mediated transformation was assayed. It was found that kanamycin (100–200 mg dm⁻³) suppressed efficiently callogenesis, root formation and shoot proliferation. An estimation of effect of kanamycin (200 mg dm⁻³) and ticarcillin (500 mg dm⁻³) on morphogenesis was performed using regeneration medium. The inhibitory effects observed suggest that these conditions could be used inAgrobacterium transformation/selection system. Communicated by J. TUPY     

Somatic embryogenesis and plant regeneration of <Emphasis Type="Italic">Abelmoschus esculentus</Emphasis> through suspension culture

A simple and reliable protocol for regeneration of okra through somatic embryogenesis from suspension cultures has been developed. Embryogenic callus was obtained from hypocotyl explants cultured on media with Murashige and Skoog (MS) salts, Gamborg (B5) vitamins, 2.0 mg dm⁻³ 2,4-dichlorophenoxyacetic acid (2,4-D), 1.0 mg dm⁻³ naphthaleneacetic acid (NAA), 25 mg dm⁻³ polyvinylpyrrolidone and 30 g dm⁻³ sucrose. More number and high frequency of healthy embryoids appeared individually in suspension culture containing MS salts, B5 vitamins, 2.0 mg dm⁻³ 2,4-D and 1.0 mg dm⁻³ kinetin. Formation of cell clusters from the single cells was clearly noticed during ontogeny. Matured embryos at the cotyledonary stage were transferred to agar solidified medium for germination. The best conversion of embrya into plantlets (67.3 %) was recorded on media with half strength MS salts, B5 vitamins, 0.2 mg dm⁻³ benzylaminopurine (BAP) and 0.2 mg dm⁻³ gibberellic acid (GA₃). The plantlets were transferred to soil and hardened in the plastic pots. After proper acclimatization, the plantlets regenerated through somatic embryogenesis were compared to seed grown plants to observe any variation.     

Direct shoot regeneration from leaf explants of <Emphasis Type="Italic">Spilanthes acmella</Emphasis>

Multiple shoots of Spilanthes acmella Murr. were induced from nodal buds of in vivo and in vitro seedlings on Murashige and Skoog (MS) medium containing 1.0 mg dm⁻³ 6-benzyladenine (BA) and 0.1 mg dm⁻³ α-naphthalene-acetic acid (NAA). Adventitious shoots were successfully regenerated from the leaf explants derived from the above mentioned multiple shoots. The efficiency of shoot regeneration was tested in the MS medium containing BA, kinetin, or 2-isopentenyl adenine in combination with NAA, indole-3-acetic acid (IAA), or indole-3-butyric acid (IBA) and gibberellic acid. Maximum number of shoots per explant (20 ± 0.47) was recorded with 3.0 mg dm⁻³ BA and 1.0 mg dm⁻³ IAA. An anatomical study confirmed shoot regeneration via direct organogenesis. About 95 % of the in vitro shoots developed roots after transfer to half strength MS medium containing 1.0 mg dm⁻³ IBA. 95 % of the plantlets were successfully acclimatized and established in soil. The transplanted plantlets showed normal flowering without any morphological variation.     

Effects of leaf soluble sugars content and net photosynthetic rate of quince donor shoots on subsequent morphogenesis in leaf explants

The effects of different growth conditions (ventilated and closed vessels, medium with 0, 15 and 30 g dm⁻³ sucrose) during proliferation of donor quince (Cydonia oblonga Mill.) shoots (stage I) on net photosynthetic rate and soluble sugars content were evaluated. In order to assess the influence of these physiological parameters on morphogenesis, leaf explants harvested from donor shoots were induced to form somatic embryos and adventitious roots under ventilated and closed Petri dishes (stage II). Natural ventilation and low sucrose contents (0–15 g dm⁻³) promoted the photosynthetic rate of quince shoots whereas biomass accumulation was the highest in those shoots cultured with 30 g dm⁻³ sucrose in both vessel types and 15 g dm⁻³ sucrose under natural ventilation. Increasing sucrose content in the medium induced greater accumulation of sucrose in leaf tissues of donor shoots. The content of reducing sugars was higher than that of sucrose, and it appeared to be higher in shoots cultured under natural ventilation compared to those in closed vessels. Somatic embryogenesis and root regeneration were influenced by stage I and II treatments. A significant correlation between sucrose content in the leaves of donor shoots and the number of somatic embryos regenerated was found, suggesting that identification of biochemical and physiological characteristics of donor shoots associated with increased regeneration ability might be helpful for improving morphogenesis in plant tissue culture.     

Direct organogenesis from leaf explants of <Emphasis Type="Italic">Stevia rebaudiana</Emphasis> and cultivation in bioreactor

Shoot buds were induced directly on either side of midrib from adaxial surface of immature leaf explants in Stevia rebaudiana Bertoni five weeks after culturing in Murashige and Skoog’s nutrient medium supplemented with 8.88 μM of N ⁶-benzylaminopurine and kinetin ranging from 4.65 to 6.98 μM. Immature leaves of 0.6 to 1 cm were found to produce best response (93 %) with a highest number of 4.93 shoot buds per explant. For elongation of regenerated shoot buds, MS medium supplemented with 30 g dm⁻³ sucrose and indole-3-butyric acid (IBA) ranging from 4.92 to 7.38 μM were found most suitable. The medium was further modified to suit bioreactor cultivation of regenerated shoots wherein the use of two-fold MS salts and 60 g dm⁻³ sucrose resulted in a high biomass yield of 50.68 g dm⁻³ (m/v) accounting for about 590 micro-cuttings in three weeks. Best rooting of micro-cuttings occurred in half strength MS medium supplemented with IBA ranging from 4.92 to 7.38 μM, 15 g dm⁻³ sucrose and gelled with 0.8 % agar. Rooted plants were successfully established in substrate containing sand, Vermicompost and garden soil in equal proportions and grown in greenhouse. This is the first report on direct shoot regeneration from Stevia leaves.     

Somatic embryogenesis and regeneration of <Emphasis Type="Italic">Vigna radiata</Emphasis>

An efficient regeneration protocol via somatic embryogenesis was optimized for mung bean [Vigna radiata (L.) Wilczek; cv. Vamban 1]. Primary leaf explants were used for embryogenic callus induction in MMS medium (Murashige and Skoog salts with B5 vitamins) containing 2.0 mg dm⁻³ 2,4-dichlorophenoxyacetic acid (2,4-D), 150 mg dm⁻³ glutamine and 3 % sucrose. Fast growing, highly embryogenic cell suspensions were established from 21-d-old calli in MMS medium supplemented with 0.5 mg dm⁻³ 2,4-D and 50 mg dm⁻³ proline (Pro), and maximum recovery of globular (39.0 %), heart-shaped (26.3 %) and torpedo-stage (21.0 %) somatic embryos were observed in this medium. Mature cotyledonary-stage somatic embryos were cultured for 5 d in half strength B5 liquid medium containing 0.05 mg dm⁻³ 2,4-D, 20 mg dm⁻³ Pro, 5 μM abscisic acid, 1000 mg dm⁻³ KNO₃, 50 mg dm⁻³ polyethylene glycol (PEG 6000) and 30 g dm⁻³ D-mannitol. Mature somatic embryos were germinated after dessication for 3 d and complete development of plantlets accomplished in MMS medium containing 30 g dm⁻³ maltose, 0.5 mg dm⁻³ benzyladenine and 500 mg dm⁻³ KNO₃. Profuse lateral roots, and regeneration frequency (up to 60 %) were observed in half-strength MMS medium containing 0.5 mg dm⁻³ indolebutyric acid (IBA). The regenerated plants were grown to fruiting and were morphologically normal and fertile.     

Introduction of <Emphasis Type="Italic">OsglyII</Emphasis> gene into <Emphasis Type="Italic">Oryza sativa</Emphasis> for increasing salinity tolerance

Mature seed-derived embryogenic calli of indica rice (Oryza sativa L. cv. PAU201) were induced on semisolid Murashige and Skoog medium supplemented with 2.5 mg dm⁻³ 2,4-dichlorophenoxyacetic acid + 0.5 mg dm⁻³ kinetin + 560 mg dm⁻³ proline + 30 g dm⁻³ sucrose + 8 g dm⁻³ agar. Using OsglyII gene, out of 3180 calli bombarded, 32 plants were regenerated on medium containing hygromycin (30 mg dm⁻³). Histochemical GUS assay of the hygromycin selected calli revealed GUS expression in 50 % calli. Among the regenerants, 46.87 % were GUS positive. PCR analysis confirmed the presence of the transgene of 1 kb in 60 % of independent plants. Further, these plants have been grown to maturity in glasshouse. In vitro screening for salt tolerance showed increase in fresh mass of OsglyII putative transgenic calli (185.4 mg) as compared to control calli (84.2 mg) on 90 mM NaCl after 15 d. When exposed to 150 mM NaCl, OsglyII putative transgenic plantlets showed normal growth while the non-transgenic control plantlets turned yellow and finally did not survive.     

<Emphasis Type="Italic">In vitro</Emphasis> bud regeneration of <Emphasis Type="Italic">Carthamus tinctorius</Emphasis> and wild <Emphasis Type="Italic">Carthamus</Emphasis> species from leaf explants and axillary buds

The organogenic competence of leaf explants of eleven Carthamus species including C. tinctorius on Murashige and Skoog (MS) medium supplemented with different concentrations of thidiazuron (TDZ) + α-naphthaleneacetic acid (NAA) and 6-benzyladenine (BA) + NAA was investigated. Highly prolific adventitious shoot regeneration was observed in C. tinctorius and C. arborescens on both growth regulator combinations and the shoot regeneration frequency was higher on medium supplemented with TDZ + NAA. Nodal culture of nine Carthamus species on media supplemented with BA and kinetin (KIN) individually revealed the superiority of media supplemented with BA over that of KIN in facilitating a higher shoot proliferation index. Proliferating shoots from axillary buds and leaf explants were transferred to medium supplemented with 1.0 mg dm⁻³ KIN or 0.5 mg dm⁻³ BA for shoot elongation. Elongated shoots were rooted on half-strength MS medium supplemented with 1.0 mg dm⁻³ each of indole-butyric acid (IBA) and phloroglucinol. The plantlets thus obtained were hardened and transferred to soil.     

Effect of sucrose application,minerals, and irradiance on the <Emphasis Type="Italic">in vitro</Emphasis> growth of <Emphasis Type="Italic">Cistus incanus</Emphasis> seedlings and plantlets

To study the effect of sucrose on the sink-source relationship in in vitro-grown plants, Cistus incanus seedlings and plantlets were grown horizontally in a two-compartment Petri dish (split dish), with the root system in one compartment and the shoot in the other. Shoots and roots were exposed to different sucrose concentrations (0–30 g dm⁻³), two irradiance levels (25 and 160 μmol m⁻²s⁻¹) and the presence or absence of a minimum medium containing minerals and vitamins (M medium). Root and shoot biomass of the seedlings was enhanced by an increase in irradiance when the growth medium was not supplemented with sucrose indicating the role of photosynthesis in biomass production. When sucrose was added to either organ growth was enhanced as well. In the presence of sucrose in the root compartment, sucrose applied to the shoot compartment enhanced growth of both organs under low irradiance, while under high irradiance, sucrose had no further additive effect. In the absence of sucrose in the root compartment, the enhancement of root biomass by sucrose added to the shoot compartment was lower under high irradiance than under low irradiance. The response of Cistus plantlets to sucrose and irradiance differed from that of seedlings, probably reflecting a greater susceptibility of the plantlets to sucrose feedback inhibition on photosynthesis and biomass accumulation. The decrease in root and shoot growth when M medium was added to the shoot compartment and the relatively better growth of these organs when the roots were supplied with minerals and the shoot with sucrose, indicate that growth of the two organs in our experimental set-up was regulated by opposing fluxes of C and nutrients.