Rapid multiplication of Dalbergia sissoo Roxb.: a timber yielding tree legume through axillary shoot proliferation and ex vitro rooting

Effect of Organic Amendments in Soil on Physiological and Biochemical Attributes of Vachellia nilotica and Dalbergia sissoo under Saline Stress

Vachellia nilotica (L.) P.J.H. Hurther & Mabb. and Dalbergia sissoo Roxb. are two of the most important multipurpose agroforestry tree species of the Indian sub-continent, but their growth in saline soils is greatly reduced. Recently, organic amendments have showed the potential to increase plant growth in salt-affected soils; however, the influence of using these amendments for growing the above-mentioned tree species under saline conditions is not yet quantified. Therefore, an experiment was devised to analyze the interactive effects of organic amendments in saline soils on the growth of V. nilotica and D. sissoo. Under controlled conditions, a pot experiment was conducted in sandy loam saline soils (EC = 20.5 dSm⁻¹). Organic amendments from four diverse sources: farmyard manure (FYM), poultry manure (PM), slurry (SL), and farmyard manure biochar (FYMB) were employed in this study. At the harvesting time, data regarding morphological, physiological, ionic, and biochemical parameters were obtained. The current study results indicated that both tree species reacted differently, but positively, to diverse applied amendments. The maximum increment in total above-ground biomass, total below-ground biomass, and shoot length for V. nilotica (163.8%, 116.3%, and 68.2%, respectively) was observed in FYM amended soils, while the maximum increment for D. sissoo (128%, 86%, and 107%, respectively) was observed in FYMB amended soils, as compared to control. Minimum plant growth of both species was observed in untreated soils (saline soils). Likewise, the maximum potassium ion and minimum sodium ion concentrations were present in the root and shoots of plants (both species) treated with FYMB. The use of organic amendments resulted in decreased concentrations of malondialdehyde and hydrogen peroxide, and increased concentrations of antioxidant enzymes such as SOD, POD, and CAT. Moreover, higher photosynthetic rates and stomatal conductance were observed in the plants grown in amended soils. The findings of this study can be used to include the above-mentioned high-value tree species for future afforestation programs under saline conditions.

In vitro propagation from axillary buds of the endangered tree Dalbergia congestiflora Pittier (Fabaceae)

Dalbergia congestiflora Pittier is a woody plant species grown in Mexico and Central America and widely used as timber wood and medicinal material. Since D. congestiflora is an endangered species, an in-vitro micropropagation technique is needed for mass propagation of D. congestiflora plantlets. Nodal segments of D. congestiflora stem cuttings grown in greenhouse conditions were disinfected with an appropriate protocol and in vitro established on Murashige and Skoog medium (MS) supplemented with 0.05 mg l^-1 benzylaminopurine (BA). The explants showed 10% contamination with 90% survival, and the initial shoot was regenerated in 90% of them. Axillary buds of 45-day-old initial shoots were cultured on MS containing BA (0, 0.05, 0.1, 0.5, 1, 1.5 and 2 mg l^-1) singly or in combination with α-naphthaleneacetic acid (NAA) (0, 0.1, 0.5 and 1 mg l^-1). A higher shoot number (9.6 shoots/explant) was obtained on MS with 1 mg l^-1 BA and 0.1 mg l^-1 NAA. Rooting was investigated using half-strength MS, 2% sucrose and different concentrations of indole butyric acid (IBA) (0, 0.1, 0.5 and 1 mg l^-1). After 30 days of culture, developing shoots were elongated and rooted in culture medium without IBA, with production of 3.2 roots/shoot. Micropropagated plantlets of D. congestiflora were successfully transplanted and acclimatized to a mixture of peat moss and perlite (2 : 1) with 100% relative humidity in greenhouse conditions with 80% survival at 30 days of culture. This micropropagation protocol will contribute to the conservation of D. congestiflora, and assure the mass propagation for sustainable usage of this species.

Shoot tip necrosis of in vitro plant cultures: a reappraisal of possible causes and solutions

Shoot tip necrosis is a physiological condition that negatively impacts the growth and development of in vitro plant shoot cultures across a wide range of species. Shoot tip necrosis is a physiological condition and disorder that can arise in plantlets or shoots in vitro that results in death of the shoot tip. This condition, which can spread basipetally and affect the emergence of axillary shoots from buds lower down the stem, is due to the cessation of apical dominance. STN can occur at both shoot multiplication and rooting stages. One of the most common factors that cause STN is nutrient deficiency or imbalance. Moreover, the presence or absence of plant growth regulators (auxins or cytokinins) at specific developmental stages may impact STN. The cytokinin to auxin ratio within an in vitro plant can be modified by varying the concentration of cytokinins used in the culture medium. The supply of nutrients to in vitro shoots or plantlets might also affect their hormonal balance, thus modifying the occurrence of STN. High relative humidity within culture vessels and hyperhydricity are associated with STN. An adequate supply of calcium as the divalent cation (Ca²⁺) can hinder STN by inhibiting the accumulation of phenolic compounds and thus programmed cell death. Moreover, the level of Ca²⁺ affects auxin transport and ethylene production, and higher ethylene production, which can occur as a result of high relative humidity in or poor ventilation of the in vitro culture vessel, induces STN. High relative humidity can decrease the mobility of Ca²⁺ within a plant, resulting in Ca²⁺ deficiency and STN. STN of in vitro shoots or plantlets can be halted or reversed by altering the basal medium, mainly the concentration of Ca²⁺, adjusting the levels of auxins or cytokinins, or modifying culture conditions. This review examines the literature related to STN, seeks to discover the associated factors and relations between them, proposes practical solutions, and attempts to better understand the mechanism(s) underlying this condition in vitro.

In vitro propagation, ex vitro rooting and leaf micromorphology of Bauhinia racemosa Lam.: a leguminous tree with medicinal values

A micropropagation system for Bauhinia racemosa Lam. was developed involving axillary shoot proliferation and ex vitro rooting using nodal explants obtained from mature tree. MS medium with 3.0 mg l^-1 BA (6-benzyladenine) was optimum for shoot bud induction. For shoot multiplication, mother explants were transferred repeatedly on medium containing low concentration of BA (0.75 mg l^-1). Number of shoots was increased up to two passages and decreased thereafter. Shoot multiplication was further enhanced on MS medium containing 0.25 mg l^-1 each of BA and Kin (Kinetin) with 0.1 mg l^-1 of NAA (α-naphthalene acetic acid). Addition of 0.004 mg l^-1 TDZ (thidiazuron) increased the rate of shoot multiplication and 21.81 ± 1.26 shoots per culture vessel were obtained. In vitro regenerated shoots were rooted under ex vitro conditions treated with 400 mg l^-1 IBA (indole-3-butyric acid) for 7 min on sterile soilrite. After successful hardening in greenhouse, ex vitro rooted plants were transferred to the field conditions with ≈85% of survival rate. Micromorphological changes were observed on leaf surface i.e. development of vein density and trichomes and stomatal appearance, when plants were subjected to environmental conditions. This is the first report on in vitro regeneration of B. racemosa from mature tree.

A high-frequency in vitro multiplication, micromorphological studies and ex vitro rooting of Cadaba fruticosa (L.) Druce (Bahuguni): a multipurpose endangered medicinal shrub

An efficient and reproducible in vitro propagation protocol has been established for Cadaba fruticosa (L.) Druce. Surface-sterilized nodal stem segments of mature plant were used as explants for culture establishment. Multiple shoots were optimally differentiated from the nodal stem explants through bud breaking on Murashige and Skoog (1962) medium containing 3.0 mg l(-1) benzyladenine (BA). The effect of different plant growth regulators and minerals were studied on different stages of micropropagation procedure (i.e., explant establishment, shoot multiplication/growth and ex vitro rooting). Additionally, for enhancing shoot multiplication during subculture, MS medium was modified (MMS) with higher levels of magnesium, potassium and sulphate ions. Out of these, MMS3 medium containing 0.25 mg l(-1) each of BA and Kin (N6-furfuryladenine), with 0.1 mg l(-1) NAA (α-naphthalene acetic acid) was found the best for shoot multiplication (42.45 ± 3.82 per culture vessel). The in vitro regenerated shoots were rooted under ex vitro conditions on treating the shoot base with 500 mg l(-1) of IBA (indole-3 butyric acid) for 3 min on sterile Soilrite®. The ex vitro rooted plants were hardened in the greenhouse and transferred to the field with ≈85 % survival rate. There were not any visual differences between wild and micropropagated plants in the field, although the later underwent significant changes during acclimatization. Micromorphological changes on leaf surface characters from in vitro to acclimatized plantlets were studied in terms of development of glandular trichomes, changes in vein spacing and vein structure in order to understand the nature of plant responses towards environmental conditions. The method developed and defined can be applied for commercial cultivation, which may be important for extraction of bioactive compounds and may facilitate conservation of this multipurpose endangered medicinal shrub.

Micropropagtion of Terminalia bellerica from nodal explants of mature tree and assessment of genetic fidelity using ISSR and RAPD markers

The present study reports an efficient in vitro micropropagation protocol for a medicinally important tree, Terminalia bellerica Roxb. from nodal segments of a 30 years old tree. Nodal segments taken from the mature tree in March-April and cultured on half strength MS medium gave the best shoot bud proliferation response. Combinations of serial transfer technique (ST) and incorporation of antioxidants (AO) [polyvinylpyrrolidone, PVP (50 mg l(-1)) + ascorbic acid (100 mg l(-1)) + citric acid (10 mg l(-1))] in the culture medium aided to minimize browning and improve explant survival during shoot bud induction. Highest multiplication of shoots was achieved on medium supplemented with 6-benzyladenine (BA, 8.8 μM) and α-naphthalene acetic acid (NAA, 2.6 μM) in addition to antioxidants. Shoot elongation was obtained on MS medium containing BA (4.4 μM) + phloroglucinol (PG, 3.9 μM). Elongated shoots were transferred to half strength MS medium containing indole-3-butyric acid (IBA, 2.5 μM) for root development. The acclimatization of plantlets was carried out under greenhouse conditions. The genetic fidelity of the regenerated plants was checked using inter simple sequence repeats (ISSR) and randomly amplified polymorphic DNA (RAPD) analysis. Comparison of the bands among the regenerants and mother plant confirmed true-to-type clonal plants.