Modeling individual leaf area of ginger (Zingiber officinale Roscoe) using leaf length and width

Leaf area estimation is an important biometrical observation one has to do for comparing plant growth in field and pot experiments. In this study, a leaf area estimation model was developed for ginger (Zingiber officinale Roscoe), using linear measurements of leaf length (L) and maximum width (W). Leaves from five ginger varieties (Varada, Rejatha, Mahima, Maran and Himachal) were used to develop the model in 2006–2007. The actual leaf area (LA) was measured with a leaf area meter (LI-3100, LI-COR, Lincoln, NE, USA) and taken as reference LA. The linear measurements were used to build linear (LA = a + b × L × W) and power models (LA = α × (L × W)^β) for each variety, as the modeling among variety were not different from each other, data for all five varieties have been pooled and compared with earlier models by graphical procedures and statistical criteria such as Mean Square Error (MSE), Root Mean Square Error (RMSE) and Chi-square (χ²). The selected model was validated during 2007–2008. The validation data set was used to produce a validation model for each variety by re-estimating the model parameters to develop the estimation model and the models were compared for consistency. The predicted LA (PLA) was compared with observed LA (OLA) by graphical procedures and lack of agreement was evaluated by calculating the relative bias, estimated by the mean of differences (d) and the standard deviation (SD) of the differences. Normality test was carried out by Spearman's rank correlation coefficient (r_s) and residuals were normally distributed. Finally, the proposed model for leaf area estimation of ginger is LA = −0.0146 + 0.6621 × L × W, R² = 0.997. This model can be reliably used for estimating leaf area of ginger non-destructively. The same equation can be extrapolated to all varieties and land races of ginger as it is vegetatively propagated crop with narrow genetic variability.     

Optimal pollination environment of tetraploid ginger (Zingiber officinale Roscoe) evaluated by in vitro pollen germination and pollen tube growth in styles

Pollen germination percentages in vitro of a tetraploid ginger (Zingiber officinale Roscoe), ‘4×Sanshu’, tended to be highest at around 20°C. Pollen tube growth in the styles was greatly enhanced at 17°C, i.e., pollen tubes penetrated into the entire stylar length in 66.7% of the styles used. Pollen stored for at least 3 h under 40–80% relative humidity (RH) almost completely lost its germinability, whereas pollen incubated for up to 3 h under 100% RH retained a relatively higher germinability. Moreover, the pollen germinability that was lowered under 40–80% RH did not recover when the pollen was re-humidified for 2 h under 100% RH before inoculation onto a medium. When stigmas were pollinated with fresh pollen at 17°C under 100% RH, pollen tubes penetrated into the entire stylar length in 26.7% of the styles tested. Under 40–80% RH, however, pollen tubes stopped growing at the middle or the base of styles. From these results, I concluded that the optimal pollination environment of the tetraploid ginger was at 17–20°C under 100% RH.     

Reducing oxidative browning during in vitro establishment of Protea cynaroides

Oxidative browning is one of the reasons why Protea cynaroides is not being extensively propagated via tissue culture techniques. The reduction of oxidative browning was best achieved by stirring the explants for 1 h in an antioxidant solution mixture containing 100 mg l⁻¹ ascorbic acid and 1500 mg l⁻¹ citric acid before inserting them into the medium. In combination with this antioxidant solution, in vitro establishment was highly successful where 100% bud growth was achieved by explants growing under 16 h photoperiod.     

A simple method for large-scale propagation of Dendrocalamus asper

The influence of position of cuttings, auxin treatments and seasonal variation on adventitious rooting of Dendrocalamus asper, a multipurpose edible bamboo of horticultural value, was examined. Single node proximal (culm) and distal (culm-branch) cuttings were collected during the months of April–June and treated for 24 h with water or 2 mM auxin (indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) and naphthalene acetic acid (NAA)). The treated cuttings were planted horizontally in sand beds and maintained under misting conditions for 2 months. Culm cuttings exhibited better adventitious rooting than culm-branch cuttings and the month of May proved to be the best for rooting of both types of cuttings. Auxin treatments also influenced adventitious rooting and their effectiveness was in the order: NAA>IBA>IAA. The interaction among auxin, position of cuttings and month of collection was also found to be significant on root induction and differentiation. Single node culm cuttings, without auxin treatment, resulted in 98% plantlets in May and 67% plantlets in June, and emerged as a suitable material for large-scale vegetative propagation. Administration of IAA or NAA to abundant culm-branch cuttings of low commercial utility (collected in May) also produces ≥50% plantlets.     

Micropropagation and accumulation of essential oils in wild sage (Salvia fruticosa Mill.)

A protocol for in vitro propagation of the wild three-lobed sage (Salvia fruticosa Mill.) (Synonym, Salvia triloba L.) was developed. Shoot tips were excised from in vitro seedlings and established on MS, Nitch and Nitch (NN), or B5 medium. For shoot proliferation, in vitro nodal and apical explants were cultured on MS medium containing 0.25–2 μM 6-benzylaminopurine (BA), 6-furfurylaminopurine (kinetin), or thidiazuron (TDZ). Proliferated microshoots were rooted on MS medium supplemented with 2.7–11.4 μM indole-3-butyric acid (IBA), indole-3-acetic acid (IAA), or α-naphthaleneacetic acid (NAA). Results indicated that shoots established at 100% regardless of media type, however, shoot height, nodes per shoot, and leaf number were highest for explants established on MS medium compared to NN or B5. Number and height of proliferated shoots, nodes per shoot, and leaf number were highest for nodal explants cultured on a medium containing 0.75 μM BA. Microshoots cultured on a medium supplemented with 2.7 μM IBA exhibited the highest rooting percentage compared to those cultured with IAA or NAA. Essential oil composition in microshoots and shoots of greenhouse-grown plants was determined by gas chromatography/mass spectrometry. The major essential oils detected in both plant materials were α-pinene, 1,8-cineole, camphor, and borneol. No α-thujone or β-thujone was detected. The content of essential oils, camphor, and borneol were higher in the microshoots than in shoots of greenhouse-grown plants.     

Role of bioinoculants in development of salt-resistant saplings of Morus alba (var. sujanpuri) in vivo

Pot experiments were conducted for the development of salt-resistant saplings of Morus alba (var. sujanpuri) involving bioinoculants, namely arbuscular mycorrhizal (AM) fungi, Azotobacter and indole butyric acid (IBA). The IBA and sodium chloride (NaCl) concentrations were optimized prior to the experiments. By using both low and high concentrations, 15 ppm IBA and 0.05% NaCl (w/v) were found to be optimum in acting synergistically with AM fungi and Azotobacter and also for increasing all the growth parameters and microbial count in the rhizosphere. For in vivo development of salt-resistant saplings, the optimal concentration of IBA, along with AM fungi and Azotobacter in different combinations, was applied. The saplings were irrigated regularly with 0.05% NaCl water. Although growth parameters such as AM infection percentage, AM spores per 100 g soil and Azotobacter cells/g soil were affected by NaCl watering, the inoculation of both bioinoculants significantly enhanced survival percentage of saplings from 25 to 50% under salt stress. Maximum survival (55%) of saplings was found with IBA (15 ppm)+AM fungi+Azotobacter.     

Effects of thermoperiodicity and plant population density on stem and flower elongation, leaf development, and specific fresh weight in single stemmed rose (Rosa hybrida L.) plants

Thermoperiodicity, i.e. growth in the alternating temperature regime with the same diurnal mean compared with growth at the constant temperature at which optimal growth occurs, was studied at three plant population densities in four cultivars of Rosa hybrida L. Single-node cuttings with five-leaflet leaves were excised and grown as single-stemmed rose plants at an average photosynthetic photon flux density of about 260 μmol m⁻² s⁻¹ and supplied with carbon dioxide at about 1000 μmol mol⁻¹. The optimal constant temperature regime was 22 °C day (20 h)/22 °C night (4 h); alternating temperatures were 23 °C day (20 h)/18 °C night (4 h). The plant population densities were 100, 131 and 178 plants m⁻² of bench area. Thermoperiodicity was absent, or could not be detected, in the parameters related to the growth period, the formation of fresh biomass, the bloom quality, and most parameters related to shoot elongation. However, classic thermoperiodic effects of alternating regime were significant in the cultivars Red Velvet and Sonia, with shoot elongation promoted (7.1 and 10.5%, respectively) in the growth phase from onset of axillary bud growth until the flower bud became visible. Compared with the other two cultivars, plants of Red Velvet and Sonia tended to develop longer internodes. The results, obtained concurrently at three different plant population densities, suggest that thermoperiodicity can affect (single-stemmed) plant growth and development in R. hybrida. Increased plant population density also increased plant height at visible flower bud, but the bloom quality, expressed as specific fresh weight, and the flower height at anthesis was decreased at the highest density. Increased plant population density increased the number of five-leaflet leaves developed in Red Velvet, but had no effect on leaf number in Texas and Sonia, while, in Lambada the leaf number was decreased at the highest density.     

Influence of medium composition and vessel ventilation on in vitro propagation of Phillyrea latifolia L.

Micropropagation of Phillyrea latifolia L. a wild species present in Mediterranean coastal areas having drought and salt tolerance was performed using explants from adult plants. Shoots were induced from nodal explants on the Rugini’s initial medium (IM). Then these were proliferated on either Rugini olive medium (OM) or Linsmaier and Skoog (LS) medium, each supplemented with 2.22 μM 6-benzylaminopurine (BA) or 4.56 μM zeatin (Z). Rooting (66.1±11%) was induced on shoots grown in perlite soaked with half-strength Rugini olive proliferation medium (OMr) containing 2.69 μM α-naphthaleneacetic acid (NAA) and 160 mg l⁻¹ putrescine. Both shoot multiplication and rooting were performed using Magenta^® GA-7 (Sigma) vessels either non-permeable or permeable to gas exchanges. Contamination (about 40%) was observed during the first five passages notwithstanding the addition of cefotaxime to the culture medium, but a high proliferation rate (90%) of explants provided enough healthy plant material. The highest shoot proliferation was observed on LS medium and zeatin whereas the presence of the ventilated filters reduced fresh weight of explants growing on LS media and did not affect shoot growth on OM media. During rooting, the use of ventilated vessels in comparison with the closed ones enhanced development of roots, and doubled the dry weight of plantlets. The vessel ventilation combined with the artificial substrate (perlite) was beneficial for in vitro acclimatization of rooted Phillyrea plantlets.     

Clone identification and genetic relationship among vine cacti from the genera Hylocereus and Selenicereus based on RAPD analysis

Clones of Hylocereus and of Selenicereus species were distinguished from each other by the banding pattern generated by one to nine 10-mer oligonucleotide primers in the random amplified polymorphic DNA (RAPD) reaction. RAPD analysis was also applied to estimate the genetic relationship among five Hylocereus and nine Selenicereus species. A dendrogram was constructed based on a data matrix of 173 polymorphic bands originated by nine primers. Two groups were identified, one consisting of Hylocereus species and the other consisting of Selenicereus species. These results are consistent with the accepted taxonomic classification of the genera studied. The principal coordinate analysis (PCO), i.e. the plot drawn on the basis of the RAPD data, clearly distinguished between three groups, namely, Hylocereus species, S. megalanthus and the rest of the Selenicereus species studied. PCO thus strongly support the notion that the tetraploid S. megalanthus is an exception among the Selenicereus group. The RAPD results support our hypothesis regarding the allopolyploid (rather than autopolyploid) origin of this species.     

Effect of various polyamines on production of protocorm-like bodies in orchid—Dendrobium ‘Sonia’

Polyamines, putrescine, spermidine and spermine all at three concentrations viz., 0.2, 0.4 and 1.0 mM were tested, by supplementing to MS basal+4.44 μm BAP medium. The explant used was fractionated plb. Ethylene and methane was measured at 20 and 40 days after inoculation (DAI). Among various polyamines tested, maximum number of plb’s (protocorm-like bodies) were produced in putrescine 0.4 mM treatment. Increase (1.0 mM) or decrease (0.2 mM) in concentration caused a decrease in the production of plb’s. All spermidine and spermine treatments resulted in the production of less number of plb’s than control. No ethylene evolution was observed in any of the polyamine treatments. However, methane evolution was observed in all the polyamine treatments. The absolute amounts, of methane evolved could not be related to the observed plb’s production response. However, when the evolution of methane was more than 1 nmol per gram FW h⁻¹, poor plb’s production was observed.     

Callus induction and plant regeneration from cotyledonary explants of ash gourd (Benincasa hispida L.)

A protocol for the production of complete plantlets through multiple shoots from the cotyledon-derived calli of ash gourd (Benincasa hispida L.) is described. The embryos were excised from mature seeds and cultured on Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurin (BAP, 1–5 μM). After 10 days the well-developed green cotyledons from the growing embryos were isolated and cultured on MS medium fortified with 2,4-D (1–6 μM). The cultured cotyledons gave rise to luxuriantly growing calli after 6 weeks. These calli were subcultured on MS medium supplemented with various concentrations of BAP (1–6 μM) alone or in combination with naphthalene acetic acid (NAA, 0.2 and 0.5 μM) for regeneration. The regenerated shoots were multiplied and rooted on quarter strength MS medium supplemented with indole-3-butyric acid or NAA (1–5 μM). The rooted shoots were transplanted to soil with 90% success.     

Effect of position and orientation of leaflet explants with respect to plant growth regulators on micropropagation of Zamioculcas zamiifolia Engl. (ZZ)

Micropropagation studies on Zamioculcas zamiifolia Engl. (ZZ) as to the position and orientation of leaflet explants and plant growth regulators were carried out. Explants consisted of leaflet lamina from the basal or apical part of the leaflet with or without petiolule or midrib that were placed vertically into the medium except for the explants with midrib from the basal part of the leaflet that were placed horizontally as well. The explants were cultured on solid Murashige and Skoog medium (MS) with 30 g l⁻¹ sucrose, supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) at 2 or 4 mg l⁻¹ and 6-benzyladenine (BA) at 0 or 4.44 μM in all (four) possible combinations, or with 1-naphteleneacetic acid (NAA) at 0 or 5.38 μM and BA at 0 or 4.44 μM in all (four) possible combinations (establishment medium). The morphogenic response was direct from all types of leaflet explants and varied only with respect to different plant growth regulators of the medium: 2,4-D combined or not with BA formed somatic embryo-like structures; NAA alone produced tubers and roots; BA alone resulted mainly in leaves; NAA combined with BA produced mainly roots. The intensity of the response varied accordingly to the explant type and orientation. Explants with petiolule or midrib from the basal part of the leaflet showed the highest morphogenic response compared to explants without petiolule or midrib or to explants from the apical part of the leaflet, in all the plant growth regulator combinations used. Explants with midrib from the basal part of the leaflet placed vertically into the media showed higher morphogenic response compared to those placed horizontally on the medium surface. With the objective to regenerate plantlets, explants were subcultured on MS with NAA and BA at various concentrations based on the explant response in the establishment medium, taking into consideration the initial explant type. The initial explant type did not affect the response in the subculture. Most plantlets (a tuber with roots and one leaf with one pair of leaflets) were produced by explants with embryo-like structures induced in a medium with only 2,4-D. Explants with tubers induced in a medium with NAA gave plantlets at 65–85% when subcultured in a medium with 4.44 μM BA alone or in combination with 2.69 μM NAA. Explants with leaves induced in a medium with BA and explants with roots induced in a medium with NAA and BA gave plantlets at low percentages (20–40%). The best response was produced by explants with embryo like structures induced in a medium with only 2,4-D which gave plantlets at 100% when subcultured in the medium with 2.69 μM NAA and 2.22 μM BA. Plantlets raised in different treatments were transplanted ex vitro after 22 weeks and exhibited 80–100% survival.     

Selection of efficient arbuscular mycorrhizal fungi in the rhizosphere of cashew and their application in the cashew nursery

Mycorrhizal association in cashew (Anacardium occidentale L.) grown in five different plantation areas of South India was investigated. The soil samples were collected from all locations. Physico-chemical properties of rhizosphere soils, arbuscular mycorrhizal fungal spore count and root colonization were recorded. Species isolated were Acaulospora, Gigaspora, Glomus and Scutellospora. The mycorrhizal spore density was maximum at Thanjavur and minimum at Kudumiyamalai. Root colonization percentage oscillated between 20 and 30%. The species of Glomus, G. aggregatum Schenck and Smith, G. fasciculatum (Thaxter) Gerdemann and Trappe and G. mosseae (Nicol. and Gerd.) Gerdemann and Trappe were the most abundant in the majority of the experimental sites. Hence these three species were selected and used for artificial inoculation studies. Of the three mycorrhizal fungi G. fasciculatum significantly increased shoot length, internode number, internode length, number of leaves, stem diameter, root length and root number.     

Transformation of Brassica oleracea var. capitata with bacterial betA gene enhances tolerance to salt stress

The bacterial betA gene for biosynthesis of glycinebetaine was transferred to cabbage (Brassica oleracea var. capitata) cultivar ‘Golden Acre’ through Agrobacterium-mediated transformation of hypocotyl explants. Transgenic status was established through Southern hybridization and mRNA expression in the shoots. The transformants exhibited higher tolerance to NaCl stress compared to untransformed parent plants. In physiological assessment of salinity tolerance, transgenics showed better growth response and greater stability in maintaining plant water relations at increasing levels of salinity. These results demonstrate that engineering glycinebetaine biosynthetic pathway into cabbage can lead to enhanced salt tolerance.     

Suitability of wood fiber substrates for production of vegetable transplants II.: The effect of wood fiber substrates and their volume weights on the growth of tomato transplants

The influence of wood fiber substrates (WFS) and their volume weights (VW) on the growth of tomato transplants (Lycopersicon lycopersicum (L.) Karst. ex Farw.) were examined. No significant differences were observed for the absolute and relative growth rate of tomato transplants cultivated in WFS as compared to white peat (WP). Particularly in WFS plants showed a well developed root system. When the tomato transplants were cultivated in spring increases of VW led to a reduction of root growth, but no significant differences were observed for other plant parameters. In summer differences between weakly and strongly compacted substrate treatments for fresh mass of leaf and stem for both WFS were found. The coarse WFS also showed a significant difference in leaf area for these two treatments. Weakly compressed substrate had a faster decrease of matric potential in summer.WFS are suitable for cultivation of vegetable transplants and are a good alternative for peat-based substrates. When filling containers, moderate compression of WFS is recommended.     

Inhibition of flower stalk elongation and abnormal flower development by short-day treatment in a Japanese variety of Chinese chive (Allium tuberosum Rottler ex Sprengel)

Chinese chive is produced year-round in Japan, therefore it is important to demonstrate the relationships of short-day (SD) conditions with flower stalk elongation and flower formation for optimizing the cropping system, e.g. the increase in harvests per year. To clarify the influence of short photoperiod on flower stalk elongation and flower formation in Chinese chive, 8 h SD treatments were applied at different developmental stages of flower stalk elongation and flower formation. When the SD treatment started from vegetative or floral-initiated stages, the earlier the SD treatment started, the fewer flower stalks appeared. Also, the earlier the SD treatment started, the less the flowers bloomed and the more the flower stalk elongation was inhibited at the end of SD treatments. Many involucres did not open and withered with death of florets in SD when the SD treatment started between the umbel or flower bud differentiation and the perianth to stamen-formation stages. Also, all or part of the florets aborted and there were no complete inflorescences in the later SD treatments. We found that, in Chinese chive, the development of flower stalk elongation and flower formation were inhibited with the earlier SD treatment, after vegetative or floral-initiated stages. Furthermore, it is considered that Chinese chive needs long-day (LD) for the flower stalk elongation and inflorescence formation after the initiation of the flower bud. The plant has a qualitative LD requirement with the same photoperiodic requirement for both flower bud initiation and flower development.     

枣、酸枣授粉生物学基础研究

采用离体培养技术对27个枣品种和酸枣的枣吊花蕾量、单花花粉量、花药开裂时间、花粉发芽率以及枣和酸枣单花不同开放阶段的花粉生活力和花粉贮藏特性进行了系统研究。结果表明:(1)不同枣品种和酸枣的枣吊花蕾量、单花花粉量、花粉发芽率存在极大差异,利用数量性状的概率分级体系可将它们分别分为3级;(2)枣和酸枣的花药开裂时间在蕾黄或蕾裂期;(3)从蕾裂到瓣平期的花粉发芽率极显著的高于蕾黄期、雄蕊展平期和雄蕊下垂期;(4)花粉贮藏后发芽率表现为下降—上升—下降的大体趋势。对杂交育种中父母本的选择、花粉采集和去雄的适宜时期也进行了讨论。     

Morphogenic gradients of adventitious bud and shoot regeneration in epicotyl explants of Citrus

The in vitro responses of epicotyl explants from ‘Cravo’ rangpur lime (Citrus limonia Osb.), ‘Foster’ grapefruit (C. paradisi Macf.), and ‘Pera’ sweet orange (C. sinensis (L.) Osb.) were characterized for the first time. Further analysis was performed in ‘Cravo’ rangpur lime and ‘Foster’ grapefruit aiming to verify the in vitro morphogenesis of five distinct regions of the epicotyl under different treatments. It was observed the same general pattern of morphogenic gradient along the epicotyl axis in both citrus cultivars, with greater organogenic response as the distance of the explants from the cotyledonary node increased. This morphogenic gradient was influenced by factors related to plant material, composition of the culture medium, and conditions of incubation. The regions of the epicotyl farthest from cotyledons could be used as a source of explants in experiments of genetic transformation of the genotypes evaluated aiming to improve the efficiency of production of transgenic Citrus plants.     

Regulation of K uptake, water uptake, and growth of tomato during K starvation and recovery

In order to analyze the dynamics of growth, water and K uptake, the effects of 1, 3 and 7 days of potassium starvation and the recovery capability during 7 days afterwards were investigated in vegetative tomato plants. After 7 days of K starvation, plant dry matter was reduced by 36% compared to control plants. After 3 days of starvation plants showed a 15% reduction in dry matter and a 25% reduction in growth rate (not statistically significant). K starvation reduced leaf area and specific leaf area (SLA) and it increased leaf dry matter percentage. K starvation enhanced dry matter partitioning into the roots at the expense of the stem. Plant K concentration was reduced by K starvation with the strongest effect in the leaves and roots. When a 3-day K starvation period was followed by 7 days of recovery with full strength nutrient solution, growth and plant K concentration completely recovered, but not after 7 days of K starvation. Xylem sap flow was reduced by K starvation and after 7 days of starvation the K concentration in the sap was reduced by 60%. During the starvation period, the reduction in relative growth rate was linearly related to the plant K concentration. The critical potassium concentration in the plant (the K concentration at which relative growth rate was reduced by 10%) was determined according to the nutrient interruption technique. The critical concentration was 4.3% K which was reached after 2.5 days of K starvation while the potassium concentration of control plants was 6.3%. During recovery the dry matter growth rate seemed to be the most important factor determining K uptake.     

The inhibition of flowering by means of gibberellic acid application reduces the cost of hand thinning in Japanese plums (Prunus salicina Lindl.)

The application of gibberellic acid during flower bud induction significantly reduced flowering of ‘Black Diamond’ and ‘Black Gold’ Japanese plums. The response depended on the concentration applied and on the type of shoot. Mixed shoots had a similar response in both varieties, flowering being reduced by 40% for GA₃ 50 mg l⁻¹ and by 75–90% for GA₃ 75 mg l⁻¹ or higher concentration. With regard to spurs, GA₃ 50 mg l⁻¹ reduced flowering intensity by 40% and 25% in ‘Black Gold’ and ‘Black Diamond’, respectively, and GA₃ 75 mg l⁻¹ or higher concentration reduced flowering by 70% and 50%, respectively. This partial inhibition of flowering significantly reduced the cost of manual thinning. The best GA₃ concentration was found to be 50 mg l⁻¹, since it reduced the cost of thinning by 45–47% and increased final fruit weight by 7–33% for ‘Black Diamond’ and ‘Black Gold’, respectively. Not significant differences in yield and in mature fruit characteristics of treated trees were found compared to untreated trees.