. 2020 Sep 3;252(3):47. doi: 10.1007/s00425-020-03449-4

Table 1.

Shoot tip necrosis: observations and possible solutions*

Scientific name and cultivar	Stage, medium and observed problems	Reason(s) provided for incidence of STN	Solution provided to halt, reduce, or prevent STN, and other observations	References
Azadirachta indica A. Juss	Optimum SMM: MS + 1.11 µM BA + 1.43 µM IAA + 81.43 µM AdS. STN = UQ	Basal medium micro- and macronutrient concentration	Addition of 0.42 mM Ca(NO₃)₂, 0.70 mM Na₂SO₄, and 0.57 mM K₂SO₄	Arora et al. (2010)
Begonia homonyma Steud	Optimum SMM: MS + 15 µM BA + 5 µM NAA. STN (all on MS) = 18% (15 µM mTR + 5 µM NAA for 12 weeks → 2 µM mTR + 0.5 µM NAA for 6 weeks), 34% (15 µM TDZ + 5 µM NAA for 12 weeks → 2 µM TDZ + 0.5 µM NAA for 6 weeks), 44% (15 µM BA + 5 µM NAA for 12 weeks → 2 µM BA + 0.5 µM NAA for 6 week)	Use of PGRs. High BA conc. and/or use of BA as the CK	Use of mTR. Use half-strength MS rather than MS, reduce BA conc. to 0.5 µM and add 2 or 5 µM GA₃: STN = 10–36% in various media defined in column 2	Kumari et al. (2017)
Butea monosperma (Lam.) Taub	Optimum SGM: half-strength WPM + 5 mg/l BA (± 10 mg/l fructose). 90% STN in terminal 2–3 mm	No substantiated reason provided. Only theoretical observation with no supporting data	Addition of fructose eliminated STN in 95% of STN-positive cultures. Some phenolics were exuded from cut ends	Kulkarni and D’Souza (2000)
Castanea dentata (Marsh.) Borkh. cv. B’ville, Iowa #2, BDW	Optimum RIM: half-strength MS + AC. SEM: WPM salts + NN vitamins. SMM = 500 mg/l PVP 40 + 500 mg/l MES + 0.89 µM BA. STN = 25–67%, depending on genotype and treatment. STN reduced to 19–21% across three genotypes in replication trial	Wounding, developmental stage, genotype	Low concentration of BA (0.22 µM) at an advanced stage of root initiation reduced STN. When on SEM, wounding had no effect on STN (~ 30–38%, 13–30%, 20–25% for B’ville, Iowa #2, and BDW, respectively). STN increased to 67% and 88% in Iowa #2 and BDW, respectively, when cuttings were plated on SMM (no change for B’ville, at 38%)	Xing et al. (1997)
Castanea sativa Mill. clones 431, T-13, 812; Quercus robur L	Optimum RIM: half-strength MS + 3 mg/l IBA (7 day) or dip in 1 g/l IBA (20–60 s) for chestnut; half-strength Gresshoff and Doy (1972) basal + 0.5 g/l IBA (8 min) for oak. STN UQ (only axillary shoot development)	In SEM, when BA was removed, or in RIM, STN developed	Addition of 0.01 mg/l BA to RIM, but this reduced rooting in chestnut and oak, but axillary shoots developed marginally more (+ 1%) in chestnut clone T-13. When the cut surface of shoot tips was added to BA-impregnated agar, rooting was reduced in both trees, but axillary shoot development increased, the amount depending on the day of decapitation	Vieitez et al. (1989)
Castanea sativa Mill. cv. Garrone rosso, Clone 46	Optimum RIM: MS + 0.044 µM BA + 5 µM IBA (8 day) then same medium without IBA. STN = 23% after 8 day, 77% after 26 day for Clone 46; UQ for Garrone rosso	Ca deficiency; lack of BA	Clone 46 formed > twofold more STN than Garrone rosso (68% vs 25%). A block of agar containing 3 mM CaCl₂ and/or 5 µM BA that was placed around shoot tips eliminated or delayed STN	Piagnani et al. (1996)
Cercis canadensis var. mexicana	SMM: WPM + MS vitamins + 11.1 µM BA. STN UQ	Excessively high concentrations of 2iP (25–74 µM), TDZ (presumably 5 or 11–23 µM) and kinetin (concentration range NR)	General suggestions on how to improve shoot growth, but no specific details, or data, about how to improve STN	Mackay et al. (1995)
Corylus avellana L	Optimum SMM: half-strength Cheng (1975) basal + 25 µM BA (15 days) → same medium but + 0.5 or 2.5 µM BA (25 days); optimum RIM: half-strength liquid Cheng (1975) basal + 50 µM IBA (5 days) → same medium (solid) (15 days). STN = UQ	High IBA concentration	Reducing IBA from 50 µM at the rooting stage to 10 or 25 µM, or by reducing exposure period to IBA to 8 days	Pérez et al. (1985)
Cydonia oblonga Mill. rootstock clone C	Optimum SMM: MS + 5 µM BA. STN = 15% in SM of control cultures	Ca deficiency	Raising Ca²⁺ (in the form of Ca(NO₃)₂) from 3 to 18 mM reduced STN, but this also reduced shoot proliferation. Link between Ca deficiency and hyperhydricity unclear	Singha et al. (1990)
Cymbidium hybrid Via del Playa Yvonne	Optimum SMM: MS – MgSO₄ + Na₂SO₄. STN = 5% (control), 35%, 60%, 80% (10, 15, 20 µM SNP, respectively)	Addition of SNP, a nitric oxide donor	Nitric oxide, a positive and negative regulator of stress, could not prevent STN	Guha and Usha Rao (2012)
Dalbergia latifolia Roxb	Optimum SMM: ¾ (macro) MS or WPM + 5 mg/l BA + 0.5 mg/l NAA. STN = UQ	Tended to find STN associated with leaf abscission, but not linked to poor aeration or high humidity	Doubling Ca²⁺ concentration in MS or WPM media did not reduce STN. Solution only provided to reduce leaf abscission by adjusting the NH₄/NO₃ ratio, but not STN	Lakshmi Sita and Raghava Swamy (1993)
Dipterocarpus alatus Roxb., D. intricatus Dyer	Optimum seedling establishment: MS or WPM + 0.1 µM BA. STN = UQ	Nitrogen level	Removal of NH₄NO₃ from WPM. High humidity likely not the cause because of high aeration of vessels	Linington (1991)
Dwarf rose (Rosa gymnocarpa Nutt.) cv. Starina	Optimum RIM: auxin-free MS. Lowest incidence of STN = 6% (on RIM). When 1 mg/l IAA was added, STN increased from 6–22% to 16–62% (range caused by the treatment)	Inclusion of auxin, specifically IAA	In the absence of auxin, 2.5–10 mg/l AgNO₃ reduced the incidence of STN from 22% to 2–12%. In IAA-containing RIM, 1.5 × Ca²⁺ levels decreased STN from 58 to 28%. In IAA-containing RIM, 1.5 × Ca²⁺ levels + 2 × Mg²⁺ levels decreased STN from 58 to 24%	Podwyszyńska and Goszczyńska (1998)
Ensete ventricosum Welw. cv. Oniya	Optimum SMM: MS + 11 µM BA + 6 µM IAA	The term STN was not used	However, STN was induced since shoot tips were split vertically down the center for micropropagation. 40% of greenhouse-derived shoot tips died due to blackening (aka STN; 0% in in vitro shoot tips)	Diro and van Staden (2005)^a
Gaultheria hispidula (L.) Muhl. ex Bigelow, Rhododendron cv. Chinsayii, Rhododendron dauricum L	Optimum SMM: Anderson (1984) basal + 15.9–16.3 mg/l 2iP (across three plants). STN = UQ	Presence of BA in medium at any concentration (0.1–10 mg/l). Use of 2iP did not induce STN	No suggestions	Norton and Norton (1985)
Haloxylon persicum (Bunge ex Boiss & Buhse)	Optimum SMM: MS + 0.5 µM TDZ. STN = 100% (0 or 2 µM TDZ), 86% (0.5 µM TDZ), 90% (1 µM TDZ); all with 10 µM Kin: 74% (2 mM CaCl₂), 65% (4 mM CaCl₂), 21% (2 mM CaCl₂ + 0.1 mM H₃BO₃), 16% (4 mM CaCl₂ + 0.1 mM H₃BO₃), 23% (2 mM CaCl₂ + 0.2 mM H₃BO₃), 19% (4 mM CaCl₂ + 0.2 mM H₃BO₃)	Low Ca²⁺ and ${BO}_{3}^{-}$	Addition of 4 mM CaCl₂ + 0.1 mM H₃BO₃ + 10 µM Kin. Use of several sugars (sucrose and maltose (60–180 mM), or fructose and glucose (110–330 mM)) with 10 µM Kin did not reduce STN (range = 89–100% for all treatments), except for 120 mM sucrose (STN reduced to 84%)	Kurup et al. (2018)
Harpagophytum procumbens [(Burch) de Candolle ex Meissner]	Optimum SMM: half-strength MS + 6 mM Ca²⁺. STN = 27% (PGR-free MS), 25–35% (MS + 5 µM BA, mT or mTR), 33–62% (MS + 5 or 10 µM BA, mT or mTR + 2.5 µM IAA), 80% (half-strength MS), 20–133% (half-strength MS + 6–9 mM Ca²⁺ alone or in various combinations with 0.2–0.5 mM ${BO}_{3}^{-}$ )	High CK (BA) level. Addition of auxin (IAA)	Addition of 6–9 mM Ca²⁺ with or without 0.2–0.5 mM ${BO}_{3}^{-}$ , or only 0.5 mM ${BO}_{3}^{-}$ , and in IAA-containing medium, 5 or 10 µM mT or mTR reduced STN	Bairu et al. (2009a)
Harpagophytum procumbens [(Burch) de Candolle ex Meissner]	Optimum SMM: MS + 8.8 µM BA. STN = 88, 90, 86% (full-strength MS, NN and WPM); 29, 27, 27% (half-strength MS, NN and WPM); 14, 26, 28% (quarter-strength MS, NN and WPM); 18, 21, 25, 26% (1, 2, 3, 4% sucrose); 29, 37, 64, 76% (sucrose, glucose, fructose, maltose at 0.086 M); 19, 28% (2-week subculture; 4-week continuous culture)	High mineral content of MS, NN, or WPM. High sucrose concentration (> 3%). Use of non-sucrose sources or carbohydrates. Lack of subculture	Reducing basal media to half strength. Use of low sucrose concentration. Use of 2-week subcultures	Jain et al. (2009)
Harpagophytum procumbens [(Burch) de Candolle ex Meissner]	Same as Bairu et al. (2009a)	Active CKs may be converted to other inactive or irreversible forms of CKs, e.g., 9-glucosides	Selection of CK, and the choice of CK:auxin ration can influence endogenous level of CKs, and thus the outcome of STN	Bairu et al. (2011)
Harpagophytum procumbens [(Burch) de Candolle ex Meissner]	Optimum SMM: MS + 1.5 mg/l BA + 6.2 mg/l H₃BO₃. STN = 53% (SMM + 10 mg/l H₃BO₃), 13% (SMM + 10 mg/l H₃BO₃ + 5 mM Si in the form of sodium silicate solution)	No reason provided	Addition of Si as SiO₂	Lišková et al. (2016)
Hibiscus rosa-sinensis L. cv. Cassiopeia Wind Yellow, Caribbean Pink	Optimum SMM: MS + 2.2 µM BA. STN = UQ	Low Ca²⁺ level (independent of BA concentration)	STN only assessed visually, but photographic evidence provided	Christensen et al. (2008)
Juglans nigra L	Optimum SMM: half-strength DKW. STN = 11% or 17% in stage 1 (3–4 week culture) when Zea = 5 or 12.5 µM, respectively, (44% and 33% in stage 2, which is 5–8 week of culture). 53% STN on MS when 12.5 µM Zea was used, and measured in stage 2	Use of BA at 25 µM or Zea at 12.5 or 25 µM. Basal medium (decreasing level of STN): half-strength DKW > DKW > MS > WPM (stage 1) or MS > half-strength DKW > DKW > WPM (stage 2)	Increasing TDZ from 0.5 to 1 µM or reducing BA from 25 to 12.5 µM BA improved percentage of spontaneous shoots, i.e., reduced STN	Bosela and Michler (2008)
Lavandula angustifolia Mill. cv Provence Blue	Optimum SMM: MS + 1 µM BA (40 day subculture). STN = 10% (1320 mg/l CaCl₂), 21% (440 mg/l CaCl₂) for a single subculture; 30% (1320 mg/l CaCl₂), 51% (440 mg/l CaCl₂) for a second subculture	Low Ca²⁺ level. Subcultures	Including CaCl₂ at 1320 mg/l. Only subculture once	Machado et al. (2014)
Lens culinaris Medikus cv. Titore	Optimum SMM: MS + 0.4–0.8 mg/l. STN = 85%, 70%, 56% and 49% in MS + 0.2, 0.4, 0.6 and 0.8 mg/l BA, respectively (91%, 87%, 75% and 73% in B5; 0–3% in MS + 440 mg/l CaCl₂; 18%, 16%, 5% and 5% in B5 + 750 mg/l CaCl₂)	Low BA conc. or reduced levels of Ca²⁺	Increasing BA conc. or adding 750 mg/l CaCl₂ to basal medium	Ye et al. (2002)
Lonicera caerulea f. caerulea; L. caerulea f. edulis	SMM: 9/10 × MS + 8.9 µM BA, 2.4 µM pyridoxine HCl. STN = 17% on half-strength MS; 6% on 75% MS; 9% on MS	Insufficient micro- and macronutrients in MS; high day/night temperatures	In caerulea form, 0% STN at 24 °C/20 °C (6% at 26 °C/20 °C, 17% at 28 °C/21 °C). In edulis form, 1% STN at 24 °C/20 °C (23% at 26 °C/20 °C, 49% at 28 °C/21 °C)	Karhu (1997)
Macadamia tetraphylla L.A.S.Johnson	Optimum SMM: MS + 2 mg/l BA. RIM: SM + 3 mg/l IBA. STN in RIM: 40% at 3 mM Ca²⁺ (20%, 70%, 85% at 6, 12 and 24 mM). Mulwa and Bhalla (2000) reported 76% STN in RIM	Inadequate aeration, high humidity	Application of < 6 mM Ca²⁺ in RIM	Mulwa and Bhalla (2000); Bhalla and Mulwa (2003)
Malus × domestica (Borkh.); Camellia sinensis (L.) Kuntze; Populus tremula L. × P. alba L.; Gerbera jamesonii Bolus ex Hooker f	SMM/RIM: MS + 2.2 µM BA + 5.3 µM NAA. STN = 49, 53, 3 and 5% in shoots of apple, tea, poplar and gerbera, respectively	Lack of exogenous CK (BA) in medium; lack of endogenous hormones in plants	CK required in medium but details not provided	Kataeva et al. (1991)
Musa spp. cv. Grande Naine (GN; AAA), Dwarf Cavendish (DC; AAA), Nendran (AAB), Quintal Nendran (QN; AAB)	Optimum SMM: MS + 6.66 µM BA. STN = 27% and 29% in GN and DC after seven subcultures on SMM (18% and 19% at the rooting stage); 38% and 40% in Nendran and QN after five subcultures on SMM (26% and 27% at the rooting stage)	Low Ca²⁺ level	Reducing the culture period, modifying salt strength in basal medium, addition of various PGRs (Kin, NAA, and IBA), adjusting levels of sucrose, fructose, and AgNO₃ did not improve STN levels. Addition of 50–100 mg/l CaCl₂ for at least two subcultures after the fourth and sixth subculture (for bananas and plantains, respectively) allowed 91–97% of shoots (across all four cultivars) to be recovered (unclear if recovered shoots were free of STN)	Martin et al. (2007)
Paeonia suffruticosa Andr	SMM: WPM + 0.3% AC. STN UQ	Low Ca²⁺ level	Adding 6 mM CaCl₂ to WPM	Wang and van Staden (2001)
Pimelea spicata R.Br	Optimum SMM: half-strength MS + 0.5 or 1.0 mg/l BA. STN = 38% (MS), 73% (MS + ventilation), 18% (half-strength MS), 56% (half-strength MS + ventilation), 32% (half-strength MS + 440 mg/l CaCl₂)	Addition of Ca²⁺. Application of ventilation to culture flasks	Using half-strength MS; not ventilating flasks; not adding supplementary Ca²⁺	Offord and Tyler (2009)
Pistacia integrima × P. atlantica rootstock UCB1	Optimum SMM: MS + 0.5 mg/l BA. STN = 42% (1 × CaCl₂, 1 × H₃BO₃), 29% (1 × CaCl₂, 2 × H₃BO₃), 38% (1 × CaCl₂, 3 × H₃BO₃), 21% (1.5 × CaCl₂), 19% (1.5 × CaCl₂, 2 × H₃BO₃), 32% (1.5 × CaCl₂, 3 × H₃BO₃), 19% (2 × CaCl₂), 17% (2 × CaCl₂, 2 × H₃BO₃), 30% (2 × CaCl₂, 3 × H₃BO₃) (all × levels relative to MS)	Low Ca²⁺and ${BO}_{3}^{-}$	Increasing CaCl₂ level to 3 × MS level, and doubling MS level of H₃BO₃ reduced STN to 17%. High level of KNO₃ (2280 mg/l) with 1320 or 1650 mg/l NH₄NO₃ eliminated STN from 10% at all other concentrations	Nezami et al. (2015)
Pistacia integrima × P. atlantica rootstock UCB1	Optimum SMM: MS + 0.5 mg/l BA, Gamborg vitamins. STN = 41% (control, no CNTs), 37% (50 µg/l CNTs), 30% (100 µg/l CNTs), 23% (150 µg/l CNTs), 13% (200 µg/l CNTs)	CNTs promote or improve physiological processes	Use of 200 µg/l CNTs	Kermani et al. (2017)
Pistacia vera L. cv. Mateur	SMM: MS + 3 mg/l BA tested for STN after 5 week. STN = 100% in 28-day cultures	Ca Ca²⁺ and ${BO}_{3}^{-}$ deficiency	First STN symptoms in 12 days, affecting the whole aerial portion by 16 days. 100, 500 or 1000 µM of B, as H₃BO₃, reduced STN but 200 µM increased STN. 500 and 1000 µM B stunted shoots. Ca²⁺ as 0.3 and 3 mM CaCl₂, and 15 and 30 mM CG increased shoot number and length, but only 15 and 30 mM could reduce STN, but eliminate it. Shoots immersed in liquid medium + 15 mM Ca²⁺ prevented STN	Abousalim and Mantell (1994)
Pistacia vera L. cv. NR	SMM: unrooted shoots on MS + 4 mg/l BA after 4 week. STN = partly quantified	High humidity in culture jars slowing nutrient flow	Addition of 12 mM CaCl₂ reduced STN the most from 2.7/cultured explant to 1.1/cultured explant, but 3–24 mM was an effective range. Ca acetate could also reduce STN but also caused shoot stunting. H₃BO₃ at 100–800 µM reduced STN from 2.6 (100 µM) to 0.4 (800 µM), but above 200 µM, shoot multiplication was reduced while shoot stunting occurred at 100 and 200 µM. No Ca- or B-free controls were used. Increasing ventilation of adding a liquid medium overlay did not reduce STN	Barghchi and Alderson (1996)
Pistacia vera L. cv. NR	Optimum SMM: DKW + 5 µM BA + 0.5 µM IBA + 0.01 g/l AA. STN = 25% (DKW), 45% (MS), 60% (WPM)	Use of CG, shoot density in flasks, flask ventilation, flask volume, bottom cooling	Improvements in STN when using bottom cooling (50% STN), reducing shoot number per flask from 7 to 5 (52% STN), or use of ventilated jars with larger volume (58% STN), relative to the control (75% STN) or the addition of 3 mM CG (80% STN)	García et al. (2011)
Pistacia vera L. cv. Ohadi, Kalleghochi	SMM: unrooted shoots on MS + 4 mg/l BA + 0.25 mg/l NAA tested for STN after 4–6 weeks; callus production and media browning also observed. STN = UQ	NAA inhibited CK production; callus that formed at base of shoots used nutrients; rooted shoots may absorb nutrients; insufficient Ca²⁺ uptake	No suggestions. STN initially detected in Barghchi and Alderson (1983)	Barghchi and Alderson (1985)
Platanus acerifolia (Ait.) Willd	Optimum SMM: MS + 1.33 µM BA + 0.27 µM IAA. STN = 57% (gelled medium), 69% (liquid medium), but wide variation (~ 20–69%) depending on the genotype	Use of liquid medium	Use of solid medium (gelled with 7 g/l agar)	Alegre et al. (2015)
Populus alba L. × P. tremula L.; P. trichocarpa Torr. & A.Gray ex. Hook. × P. deltoids W.Bartram ex Marshall	Optimum SMM: WPM + 0.5 mg/l MES + 0.02 mg/l TDZ. STN in transformation experiments = UQ	${NO}_{3}^{-}$ / ${NH}_{4}^{+}$ ratio, especially < 0.8 mM ${NH}_{4}^{+}$ in medium; medium pH < 4.9; Ca deficiency	Medium without TDZ could not form shoots; after 7 days, ${NH}_{4}^{+}$ conc. decreased from 5.0 mM to 1.6 mM; use of 650 mg/l CG + 0.5 mg/l MES + 2.5 µg/l BA allowed shoot growth without STN	De Block (1990)
Portulaca grandiflora Hook	Optimum SMM: MS + 4 µM BA + 8 µM Kin. STN = 80–90% (0.1–0.4 mM B); ~ 75–100% (3, 6, 12, 18, 24 and 30 mM CG); 50–85% (3, 6, 9, 12, 24 and 30 mM CaCl₂)	Insufficient Ca²⁺ and ${BO}_{3}^{-}$	Use of 18 mM CaCl₂ reduced STN to 40%	Srivastava and Joshi (2013)
Prunus armeniaca L. cv. Helena, Lorna	Optimum SMM + RIM: QL + 1.78 µM BA + 0.2 µM IBA. STN was observed in the rooting phase (~ 65% for ‘Lorna’; ~ 75% for ‘Helena’)	No reason provided	Adding 0.2 mg/l BA reduced STN to ~ 5% in ‘Lorna’ (~ 25% for ‘Helena’), but this also reduced rooting efficiency. High rooting ability of both cultivars maintained with reduced STN when 5–20 mg/l BA added	Pérez-Tornero and Burgos (2000)
Prunus armeniaca Lam	Optimum SMM: WPM + 0.5 mg/l BA. STN = UQ, only weighted	Low ${NH}_{4}^{+}$ and ${NO}_{3}^{-}$ . Low mesos (Ca²⁺, Mg²⁺, K⁺)	Critical threshold for CaCl₂·2H₂O: 2.94x. If CaCl₂·2 H₂O > 2.94x interaction with KH₂PO₄, so it should be higher than 1.12x. Recommended ${NO}_{3}^{-}$ level: > 45 mM. Considering STN and other growth factors, optimum range of ${NO}_{3}^{-}$ is > 25 mM and ≤ 35 mM and optimum ${NH}_{4}^{+}$ /Ca²⁺ ratio is ≤ 0.8	Kovalchuk et al. (2017a, b, 2018)
Pyrus communis cvs. Old Home × Farmingdale 87, Horner 51, Winter Nelis; P. dimorphophylla; P. ussuriensis cv. Hang Pa Li	Optimum SMM: MS + 4.44 µM BA. STN = UQ, but genotype-dependent and characterized as a function of significant interactions between multiple factors	General trends: low mesos (Ca Ca²⁺, K⁺, Mg²⁺) and N caused STN. P. communis: low mesos + low Fe and N; P. dimorphophylla: high NH₄NO₃, mesos + Fe with low KNO₃; P. ussuriensis: low NH₄NO₃, KNO₃ and mesos + high Fe and micros caused STN	STN was reduced by increasing the mesos (P. communis), using low NH₄NO₃, KNO₃ and high mesos (P. dimorphophylla), and using high KNO₃ and low mesos (P. ussuriensis). STN frequently occurred simultaneously with other physiological problems such as callus induction, hyperhydricity, hypertrophy, fasciation and formation of hooked leaves	Reed et al. (2013)
Pyrus L. cv. Williams, Highland	Optimum SMM: half-strength MS or WPM + 10 µM BA + 55 µM ABA. After 4 weeks, STN was 23%, 31%, 14% and 14% in MS, ½MS, WPM and QL, respectively, for Williams (30%, 52%, 10% and 64% in Highland)	No substantiated reason provided. Level of STN differed with sampling time (2 vs 4 weeks)	Adjusting medium pH, levels of Ca²⁺, BA or GA₃ had no visible effect on STN levels in both cultivars. WPM and low levels of Ca²⁺ should be used	Grigoriadou et al. (2000)
Pyrus sp. cv Punjab Beauty; rootstocks Patharnakh (P. pyrifolia [Burm F.] Nakai), Kainth (P. pashia Buch. Ham.), Shiara (P. serotina Rehd.); wild pear (P. pyrifolia)	Optimum SMM: MS + 4.44 mM BA + 2.46 mM IBA. STN = 79% (Punjab Beauty), 50% (Patharnakh), 25% (Kainth), 18% (Shiara), 7% (wild pear)	Addition of auxins (NAA, IBA), alone or in combination, increased STN in solid or liquid medium, but response was genotype dependent: 38% in control to 40–48% in wild pear, Kainth and Punjab Beauty; 23% in control to 25–30% in Patharnakh and Shiara	Response to Ca²⁺ and ${BO}_{3}^{-}$ levels was genotype-dependent on half-strength MS. In wild pear, STN = 9% (control), 3% (3 mM Ca²⁺ + 100 µM ${BO}_{3}^{-}$ ), 56–65% (6 or 9 mM Ca²⁺ + 100 µM ${BO}_{3}^{-}$ ), 0% (1.5 mM Ca²⁺ + 100, 200, 500 or 1000 µM ${BO}_{3}^{-}$ ). Except for 1.5 mM Ca²⁺ + 200 µM ${BO}_{3}^{-}$ , all other Ca²⁺ and ${BO}_{3}^{-}$ treatments increased STN in Punjab Beauty (from 72% in control to 73–82%). In Patharnakh, STN decreased from 42% (control) to 35–36%, but increased to 50% with 9 mM Ca²⁺ + 100 µM ${BO}_{3}^{-}$ . These Ca²⁺ and ${BO}_{3}^{-}$ treatments did not increase or decrease STN in Kainth and Shiara	Thakur and Kanwar (2011)
Pyrus sp. rootstocks Pyrodwarf, OHF	Optimum SMM: MS + 2.5 mg/l BA + 0.2 mg/l IBA. STN = 0–68% (OHF), 0–27% (Pyrodwarf) across 27 media with combinations of KNO₃, NH₄NO₃, CaCl₂, MgSO₄, and KH₂PO₄, and three basal media (MS, QL, WPM)	${SO}_{4}^{-}$ ions and ${NO}_{3}^{-}$ ions affected incidence of STN the most in OHF and Pyrodwarf, respectively	Neural network modeling and regression analysis were used to assess the severity of STN and to optimize medium components to reduce the incidence of STN. After model optimization, STN estimated to be 0% in OHF and 0.2% in Pyrodwarf	Jamshidi et al. (2016)
Quercus alba L., Q. robur L., Q. rubra L	Optimum SMM: WPM + 0.2 mg/l BA (2 weeks) then 0.1 mg/l BA (4 weeks). STN (Q. rubra only) = 22% (genotype 1), 44% (genotype 2), 3–5% (both genotypes on SMM + 3 mg/l AgNO₃	No reason provided	Addition of 3 mg/l AgNO₃	Vieitez et al. (2009)
Rhododendron ‘P.J.M. Hybrids’; Rubus sp. ‘Dirkson Thornless’; Hibiscus rosa-sinensis L	Basal medium: MS (Anderson (1975) for rhododendron) + no IBA (rhododendron) or + 10 µM IBA (hibiscus, blackberry). STN: 18% decrease in hibiscus, 39% decrease in rhododendron when 10 µM IBA used; in blackberry, 21% decrease when 1 µM IBA used, or 13% increase when 10 µM IBA used	Production of autoinhibitory exudate with polyphenols from cut surface	Addition of 10 µM IBA for hibiscus and rhododendron (1 µM IBA for blackberry). Objective was not to assess shoot or root growth, only STN (measured as length of shoot tip or stem blackening). In hibiscus, as BA was increased from 0 to 10 µM, STN increased	Compton and Preece (1988)
Rhododendron cv. Dopey, Hoppy and Sneezy; Disanthus cercidifolius Maxim.; Crataegus oxyacantha L. cv. Paul’s Scarlet	Optimum SMM: WPM + 2.5 µM 2iP (Rhododendron); LS + ½ MS (macro) + 3 µM BA (Disanthus); LS + 2.5 µM BA + 0.5 µM IBA (Crataegus). STN = 33–43% (depending on light filter applied) (Crataegus); 0% at 11 or 26 µmol m⁻² s⁻¹, 13% at 55 µmol m⁻² s⁻¹, and 64% at 106 µmol m⁻² s⁻¹ (Disanthus)	High light intensity (55 or 106 µmol m⁻² s⁻¹); reduced chlorophyll content; photolysis of endogenous auxin (theory)	STN not observed in any of the three Rhododendron cultivars, which grew equally well at all light intensities. Crataegus and Disanthus cultures should be grown at low light intensities (11 or 26 µmol m⁻² s⁻¹)	Marks and Simpson (1999)
Rosa clinophylla Thory	Optimum SMM: MS + 28.3 µM AA + 26 µM CA + 58.85 µM AgNO₃. STN = 80% (control); Kn and AgNO₃ treatments = UQ	Addition of CK (Kn) at 1.16–4.64 µM to SMM	Addition of 58.85 µM AgNO₃	Misra and Chakrabarty (2009)
Rosa hybrida cv Tineke	Optimum SMM: MS + 2 mg/l BA + 0.5 mg/l NAA. STN = 0% (0 µM ACC), 6% (10 µM ACC), 13% (25 µM ACC), 31% (50 µM ACC), 38% (100 µM ACC) in the absence of IAA; 38% (0 or 10 µM ACC), 56% (25 µM ACC), 69% (50 µM ACC), 81% (100 µM ACC) in the presence of 1 mg/l IAA	Increased ethylene in response to increased levels of ACC, in the presence or absence of IAA	IAA is likely not the most suitable auxin. The use of ethylene-inhibiting compounds (STS, SNP) improved apical shoot initiation (likely eliminated STN by removing ethylene)	Park et al. (2016)
Rubus idaeus L. cv. Allgold, Erika, Polka	SMM: unrooted shoot tips on MS + 0.6 mg/l BA after 30 and 60 d. STN = partly quantified	Browning (18–45% of explants in Allgold, 5–63% in Erika, 18–58% in Polka, depending on the medium); Ca deficiency	Lowest explant browning on medium with 1 mg/l CG (following Singha et al. 1990), resulting in 100% shoot initiation and survival (65–90% in controls (no CG), depending on the cultivar). AA at 50 and 100 mg/l reduced explant browning and STN in Allgold and Polka, but increased both phenomena in Erika. Explant browning and shoot initiation negatively correlated (R = 0.997); STN was also negatively correlated with shoot survival (R = 0.811)	Amalia et al. (2014)
Salix tarraconensis Pau ex Font Quer	Optimum SMM: MS + 4.9 µM 2iP. STN (SMM) = 0% in MS or WPM without 2iP; 23–37% (MS + 0.98–9.8 µM 2iP); 50% (WPM + 0.98 µM 2iP). STN (WPM-based rooting medium) = 7% (auxin-free control); 13–27% (1.14–5.71 µM IAA); 27–60% (0.98–4.9 µM IBA); 0–7% (1.07–5.37 µM NAA)	MS medium (relative to WPM). Presence of 2iP in basal medium. Inclusion of IAA and IBA as auxins in rooting medium	Use of a low concentration of 2iP (2.46 or 4.9 µM) in WPM for SMM for low levels of STN (7%). Use of NAA as the auxin for rooting	Amo-Marco and Lledo (1996)
Solanum tuberosum L. cv Dark Red Norland	Optimum SMM: MS + 0.5 mM myo-inositol. STN = UQ	Low Ca²⁺ content	When Ca²⁺ conc. was increased from 1 µM to 3000 µM, number of axillary shoots decreased from 21 to 1. STN increased when 5 mM EGTA was added to SMM, but decreased when 204 µM strontium was added	Ozgen et al. (2011)
Solanum tuberosum L. cv. Burbank, Dark Red Norland, Atlantic, Superior, Snowden	Same as Ahmed and Palta (2017a). STN (Acros/Fischer agar) = 29%/20% (250 μM CaCl₂), 18%/13% (500 μM CaCl₂), 0%/0% (2000 μM CaCl₂) for cv. Atlantic, 29%/21% (250 μM CaCl₂), 14%/0% (500 μM CaCl₂), 7%/0% (2000 μM CaCl₂) for cv. Snowden, 45%/25% (500 μM CaCl₂), 17%/18% (1000 μM CaCl₂), 0%/6% (2000 μM CaCl₂) for cv. Burbank, 34%/23% (500 μM CaCl₂), 6%/13% (1000 μM CaCl₂), 0%/0% (2000 μM CaCl₂) for cv. Superior, 12%/6% (500 μM CaCl₂), 0%/7% (1000 μM CaCl₂), 0%/0% (2000 μM CaCl₂) for cv. Dark Red Norland, at 15 d; 79%/87% (250 μM CaCl₂), 59%/38% (500 μM CaCl₂), 6%/0% (2000 μM CaCl₂) for cv. Atlantic, 29%/28% (250 μM CaCl₂), 25%/17% (500 μM CaCl₂), 29%/14% (2000 μM CaCl₂) for cv. Snowden, 60%/31% (500 μM CaCl₂), 38%/25% (1000 μM CaCl₂), 22%/6% (2000 μM CaCl₂) for cv. Burbank, 44%/33% (500 μM CaCl₂), 11%/13% (1000 μM CaCl₂), 12%/0% (2000 μM CaCl₂) for cv. Superior, 24%/12% (500 μM CaCl₂), 6%/7% (1000 μM CaCl₂), 0%/0% (2000 μM CaCl₂) for cv. Dark Red Norland, at 23 days	Ca deficiency	Inclusion of 250–2000 μM CaCl₂	Ahmed and Palta (2017b)
Solanum tuberosum L. cv. Dark Red Norland	Optimum SIM: MS + 0.56 mM myo-inositol. STN = 56% (60 μM CaCl₂), 13% (1 μM NAA + 60 μM CaCl₂), 0% (2 μM NAA + 60 μM CaCl₂), 52% (250 μM CaCl₂), 19% (300 μM LPE + 250 μM CaCl₂), 14% (400 μM LPE + 250 μM CaCl₂), and 14% (500 μM LPE + 250 μM CaCl₂) at 15 days; 75% (60 μM CaCl₂), 23% (1 μM NAA + 60 μM CaCl₂), 13% (2 μM NAA + 60 μM CaCl₂), 62% (250 μM CaCl₂), 29% (300 μM LPE + 250 μM CaCl₂), 20% (400 μM LPE + 250 μM CaCl₂), and 24% (500 μM LPE + 250 μM CaCl₂) at 25 days	Ca deficiency	Inclusion of 300–500 μM LPE (most effective at 400 μM) in Ca-deficient (250 μM CaCl₂) medium. Inclusion of 1 or 2 μM NAA (most effective at 2 μM) in Ca-deficient (60 μM CaCl₂) medium	Ahmed and Palta (2017a)
Solanum tuberosum L. cv. Russet Burbank, Superior, Norland	Optimum SMM: MS + modified levels of Ca²⁺ (0.3, 3 or 30 mM), as CaCl₂ or Ca(NO₃)₂. STN = 72%, 62% or 48% (Russet Burbank, Superior, Norland, respectively). STN increased from 60 to 100%, 2% to 32%, and 3% to 15% when Parafilm^® was used (vs. use of conventional plastic caps) in Russet Burbank, Superior, Norland, respectively	Low Ca²⁺ content. Use of Parafilm^®	Increasing Ca²⁺ from 0.3 mM to 3 or 30 mM. STN reduced to 0–5%, 4–9% and 1–3% with 3 or 30 mM (Russet Burbank, Superior, Norland, respectively)	Sha et al. (1985)
Soymida febrifuga (Roxb.) A. Juss	Optimum SMM: MS + 2 mg/l BA + 0.2 mg/l NAA. STN = 100% (SMM); 7.5% (MS + 556 mg/l CAN + 1 mg/l vit B5); 5.7% (MS + 556 mg/l CAN + 1 mg/l vit B5 + 20 mg/l AC + 100 mg/l fructose); 3.3% (half-strength MS + 556 mg/l CAN + 1 mg/l vit B5 + 20 mg/l AC + 100 mg/l glucose); 1.9% (half-strength MS + 556 mg/l CAN + 1 mg/l vit B5 + 20 mg/l AC + 100 mg/l fructose)	Low Ca²⁺ content. Nutrient content of basal medium	Addition of CAN, vit B5, AC, glucose/fructose, usually together	Chiruvella et al. (2011)
Trichosanthes dioica Roxb	Optimum SMM: MS + 37.2 µM Kin. Optimum RIM: half-strength MS + 2.14 µM NAA. STN = 82% (SMM) vs 64% (RIM) at 42 days, but lower in earlier cultures (e.g., 16% (SMM) vs 6% (RIM) at 14 days)	Growth stage (rooting > shoot multiplication)	Supplementing SMM with 0.68 mM CaCl₂ recovered 93% of shoot cultures with STN (18–38% recovery when 0.34, 1.02 or 1.36 mM CaCl₂, or 8–24% when 0.32–1.28 mM H₃BO₃ was used)	Kishore et al. (2015)
Ulmus glabra Huds	Optimum SMM: WPM + 0.4 mg/l BA. STN = UQ	Use of MS (as opposed to WPM)	Use of 0.1 or 0.2 mg/l mT	Mirabbasi and Hosseinpour (2014)
Vitis vinifera L. cv. Arka Neelamani	Optimum SMM: MS + 1 µM IAA + 0.1 µM GA₃. STN = 36.3%, but only 1–2 years after initial culture establishment	Cuttings with large leaf area or well developed root system. Choice of explant mass and position. Possibly low availability of Ca²⁺ and Mg²⁺ in shoot tips	STN cultures had higher root: shoot ratio, more roots, and stunted plants than non-STN cultures. STN cultures had Ca²⁺ and Mg²⁺ deficiency in the shoots, but higher levels in the roots, than non-STN cultures. STN ultimately did not negatively impact micropropagation. Solution: selection of explants with medium-sized leaves and density of > 4 plants/vessel	Thomas (2000)
Vitis vinifera L. cv. red globe	Optimum SMM: half-strength MS + 1 mg/l BA + 180 mg/l CaCl₂ + 1.1 mg/l H₃BO₃. STN = 39% (2-w subculture), 68% (5-w subculture); 30% (half-strength MS + 1 mg/l BA), 39% (MS + 1 mg/l BA), 48% (half-strength MS + 2 mg/l BA), 51% (MS + 2 mg/l BA), 57% (half-strength MS + 3 mg/l BA), 67% (MS + 3 mg/l BA); (mg/l CaCl₂ + mg/l H₃BO₃): 65% (120 + 1.1), 20% (180 + 1.1), 53% (240 + 1.1), 61% (120 + 2.2), 67% (120 + 3.3)	Low Ca²⁺ (negative correlation between Ca²⁺ content and STN; R² = 0.9682). Infrequent subcultures	Adjusting/optimizing the level of BA, and addition of CaCl₂ and H₃BO₃. Frequent (shorter) subcultures. Use of half-strength MS rather than MS	Surakshitha et al. (2019)

Only studies for which data or other evidence was provided are shown; all other studies that claimed to have observed STN, but did not provide evidence or show data are discussed only in the text. Studies for which no data exist to support the claim of STN are not included in this table, but are instead discussed in the main text. Studies listed based on alphabetical botanical name of plant

2iP N⁶-(2-isopentenyl) adenine, AA ascorbic acid, AC activated charcoal, ACC 1-aminocyclopropane-1-carboxylic acid, AdS adenine sulfate, AgNO₃ silver nitrate, B boron, BA N⁶-benzyladenine (BA is used throughout even though BAP (6-benzylamino purine) may have been used in the original (Teixeira da Silva 2012), B5 Gamborg et al. (1968) medium, Ca calcium, CA citric acid, CaCl₂ calcium chloride, CAN calcium ammonium nitrate (H₄CaN₂O₃), CG calcium gluconate, CK cytokinin, CNT carbon nanotube, cv cultivar, DKW Driver and Kuniyuki walnut medium (Driver and Kuniyuki 1984), EGTA ethylene glycol tetra acetic acid, GA₃ gibberellic acid, H₃BO₃ boric acid, IAA indole-3-acetic acid, IBA indole-3-butyric acid, Kin kinetin (6-furfurylaminopurine), LPE lysophosphatidylethanolamine, LS Linsmaier and Skoog (1965) medium, MES 2-(N-morpholino)ethanesulfonic acid, mesos CaCl₂·2H₂O, KH₂PO₄, MgSO₄, Mg magnesium, MS Murashige and Skoog (1962) medium, mT meta-topolin, mTR meta-topolin riboside, NAA α-naphthaleneacetic acid, NN Nitsch and Nitsch (1969), NR not reported, PGR plant growth regulator, PVP polyvinylpyrrolidone, QL Quoirin and Lepoivre (1977), RIM root induction medium, s second(s), SEM shoot elongation medium, SGM seed germination medium, SIM shoot induction medium, SMM shoot multiplication medium, SNP sodium nitroprusside, STN shoot tip necrosis, STS silver thiosulfate, TDZ thidiazuron (N-phenyl-N'-1,2,3-thiadiazol-5-ylurea), UQ unquantified, vit vitamin, WPM woody plant medium (Lloyd and McCown 1980), Zea zeatin (6-(4-hydroxy-3-methylbut-2-enylamino)purine)

^aUnlike the majority of other studies where STN was observed after explants were plated or at different stages of in vitro multiplication, in this study, a form of STN was induced as a result of damage induced to shoot tips during explant preparation