Reduced Root Formation Research Articles

In vitro propagation of a cut flower variety Muscari armeniacum Leichtlin ex Baker through direct bulblet proliferation pathways

Muscari armeniacum is one of the important ornamental cut flowers in floriculture industry, which is native to Southern Europe, North Africa, Western Asia and Asia Minor. In this study, bulb explants (basal plate of bulb having meristems), bulb scales, and leaf segments from in vitro derived bulblets were cultured in Murashige and Skoog (MS) medium with different plant growth regulator concentrations and combinations to assess their effects on different bulblet organogenesis pathways. The results demonstrated that cytokinin in combination with auxin is required for both axillary and adventitious bulblet regeneration. Benzyladenine (BA) combined with α-naphthalene acetic acid (NAA) showed significant effects compared to other growth regulator combinations tested. The 4.0 µM BA + 2.0 µM NAA was found to be the best for axillary bulblet formation from bulb explants. Likewise, bulb and leaf segments showed the best response in adventitious bulblet organogenesis when they were cultured in BA-NAA combinations. Out of several concentrations of BA with NAA, 4.0 µM BA + 1.0 µM NAA was optimum for adventitious bulblet regeneration. Bulblets, properly isolated from both axillary and adventitious proliferation systems, showed maximum percentage of rooting on half strength MS medium containing 2.0 µM indole-3-butyric acid (IBA). However, all the auxins at more than 2.0 µM concentration showed reduced root formation through either callus formation at the base of shoots or malformation of roots. All the in vitro regenerated plantlets were successfully acclimatized under ex vitro environment with 60% survival rate using garden soil.

In vitro seed germination and multiplication of Calophyllum brasiliense

Calophyllum brasiliense is a tree species with limited natural reproduction. In vitro germination may be an alternative for obtaining high-quality seedlings. Seeds were maintained in water before surface disinfestation and compared with control seeds (i.e. not immersed), without differences between treatments. HgCl2 used during surface-disinfestation reduced contamination rates of cultures. Fungal contamination was reduced with fungicide added to culture medium (23 to 6.4%), although bacterial contamination increased (24 to 36%). In another experiment, seeds were immersed in plant preservative mixture (PPM™) prior to surface disinfestation. By combining immersion for 48 h and 2 mL L-1 in culture medium, contamination was only 6%. Seeds immersion in GA3 prior to surface disinfestation reduced root formation as concentration increased. Germination rate and GSI were reduced, respectively, from 72% and 0.129 (24 h) to 60% and 0.092 (48 h) according to exposure time to GA3. After 90 days in multiplication medium containing benzylaminopurine, average number of shoots per nodal segment was 3.4. In conclusion, in vitro germination of C. brasiliense seeds is feasible in sucrose-free WPM medium and reaches a high contamination-free rate (up to 93.3%).

Adventitious rooting on the Brazilian red-cloak and sanchezia after application of indole-butyric and humic acids

Plant regulators, as well as bioactive fractions of the organic matter, can accelerate the development and increase the efficiency of adventitious rooting in ornamental plants. We evaluated rooting in the Brazilian red-cloak (Megaskepasma erythrochlamys) and sanchezia (Sanchezia nobilis) cuttings in response to application of indole-butyric acid (IBA) and humic acids (HA). Stem cuttings of both species treated with solutions of 0, 250, 500, 1000, 2000 mg/L of IBA and 0, 10, 20, 30, 40 mmol/L of C of HA were placed in 2.0 L plastic pots containing carbonized rice husk, kept in greenhouse. Survival of cuttings, number of leaves and shoot and root fresh and dry matter were evaluated 45 days after. Data were used to run an analysis of variance. We observed the average contrasts, calculated the regression equations and estimated the concentrations that provided the best efficiency in terms of root dry matter. For IBA, 185.4 and 66.8 mg/L were the concentrations that promoted the highest root dry matter accumulation in the Brazilian red-cloak and sanchezia, respectively, with increments of 140 and 22.5% in relation to the control. HA, at 33.6 mmol L-1 of C, increased shoot fresh and dry matter in the Brazilian red-cloak, but reduced root formation compared to the control. In sanchezia, HA at 19.5 mmol L-1 of C promoted increases of 35.9% in root dry matter in relation to the control. We concluded that IBA, in the abovementioned concentrations, increased adventitious rooting in cuttings of both the Brazilian red-cloak and sanchezia, while optimal doses of HA solutions are very likely to improve adventitious rooting in sanchezia, but not in the Brazilian red-cloak.

Constitutive Expression of a XEGIP in Potato Results in Phenotypic Changes Suggesting Endogenous Inhibition of Cell Wall Growth

One mechanism for plant defense is the production of proteinaceous inhibitors that block the function of pathogen-produced cell wall-modifying enzymes. The xyloglucanase-specific endoglucanase inhibitor protein (XEGIP) is proposed to exist principally to block pathogen family 12 xyloglucan-specific endoglucanases. The role of XEGIP in plant defense was tested by generating transgenic XEGIP-overexpressing potato plants. Overexpression of an endogenous XEGIP in potato resulted in major changes in plant phenotype. Short petioles, small, thick leaves, reduced root formation, and distorted tuber shape resulted from XEGIP overexpression. Susceptibility to late blight, caused by Phytophthora infestans, was not altered. For the XEGIP tested (AY321357), there are previously unreported alterations in plant development that can be attributed to constitutive expression of XEGIP. The principal role of at least this XEGIP may be regulation of plant-encoded enzymes.

Formação in vitro de raízes em canafístula: o efeito de diferentes meios de cultivo

A canafístula [Peltophorum dubium (Spreng.) Taub.] é uma espécie florestal nativa do Brasil, dotada de características silviculturais promissoras para fins de (re)florestamento. No entanto, a produção de mudas de alta qualidade por meio da micropropagação é limitada pela reduzida formação de raízes. Em virtude disso, o presente estudo teve como objetivo avaliar o efeito de substratos alternativos ao ágar e do período de cultivo na formação in vitro de raízes de canafístula. Para tanto, foram testados, aos 30 e 60 dias de cultivo in vitro, meios de cultivo compostos por combinações dos substratos vermiculita (V), Plantmax®(P) ou areia fina (AF) ao meio nutritivo MS, contendo 10 µM de ácido 3-indol butírico (AIB), acrescido ou não de ágar (A). Obteve-se elevada sobrevivência das brotações, tanto aos 30 (92,3%) quanto aos 60 (82,6%) dias de cultivo. Em relação aos meios de cultivo, a maioria deles proporcionou uma elevada sobrevivência (91,1 a 100,0%) das brotações; constituíram exceções àqueles que continham (P). Intensa formação calogênica foi observada apenas após 60 dias de cultivo, na testemunha, que incluiu MS e (A), e naqueles outros dois tratamentos contendo (V). O melhor resultado de formação de raízes, tanto quantitativamente (36,78%) como pela qualidade das raízes, foi obtido no tratamento que incluiu (V) e (A), além de MS, aos 60 dias de cultivo. Com a utilização de (V) no meio de cultivo, há intensa formação de calos, aos 60 dias de cultivo, porém, também há maior formação de raízes e melhoria na qualidade do sistema radicular, quando este substrato é combinado ao meio nutritivo MS.

Modification of tobacco plant development by sense and antisense expression of the tomato viroid-induced AGC VIIIa protein kinase PKV suggests involvement in gibberellin signaling

BackgroundThe serine-threonine protein kinase gene, designated pkv (protein kinase- viroid induced) was previously found to be transcriptionally activated in tomato plants infected with the plant pathogen Potato spindle tuber viroid (PSTVd). These plants exhibited symptoms of stunting, and abnormal development of leaf, root, and vascular tissues. The encoded protein, PKV, is a novel member of the AGC VIIIa group of signal-transducing protein kinases; however, the role of PKV in plant development is unknown. In this communication, we report the phenotypic results of over expression and silencing of pkv in transgenic tobacco.ResultsOver expression of pkv in Nicotiana tabacum cv. Xanthi (tobacco) resulted in stunting, reduced root formation, and delay in flowering, phenotypes similar to symptoms of PSTVd infection of tomato. In addition, homozygous T2 tobacco plants over expressing PKV were male sterile. Antisense expression of pkv, on the other hand, resulted in plants that were taller than non-transformed plants, produced an increased number of flowers, and were fertile. Exogenous application of GA3 stimulated stem elongation in the stunted, sense-expressing plants. PKV sense and antisense expression altered transcript levels of GA biosynthetic genes and genes involved in developmental and signaling pathways, but not genes involved in salicylic acid- or jasmonic acid-dependent pathways. Our data provide evidence suggesting that PKV plays an important role in a GA signaling pathway that controls plant height and fertility.ConclusionWe have found that the over expression of the tomato protein kinase PKV resulted in stunting, modified vascular tissue development, reduced root formation, and male sterility in tobacco, and we propose that PKV regulates plant development by functioning in critical signaling pathways involved in gibberellic acid metabolism.

Morphological and Physiological Changes in Transgenic Chrysanthemum morifolium Ramat. ‘Ogura-nishiki’ with rolC

The effects of rolC on morphogenesis of Chrysanthemum morifolium Ramat. ‘Ogura-nishiki’ were studied. The ray flowerets in the rolC-transformed plants were shorter than those in wild-type plants, but the transformation enhanced outgrowth of lateral shoots and reduced internode elongation. Studies on adventitious shoot and root formation from leaf segments revealed that the rolC transgene led to reduced root formation but enhanced adventitious bud formation. This enhanced cytokinin-like activity was consistent with phenotypes observed in the rolC-transformed plants.

In Vitro Morphogenesis from Ovaries of Hippeastrum X hybridum

investigated. Bulblet formation rates and number of bulblets were excellent when th~ concentrations of naphthyl acetic acid (NAA) and N-benzyladenine (BA) were the same. The combination of 5 mgl-* 2,4-dichlorophenoxyacetic acid (2,4-D) with 0.02-2 mgl-* thidiazuron (TDZ) induced somatic embryogenesis with high rate and the combination of 5 mgl-' 2,4-D and 2 mgl-* TDZ gave the greatest number of somatic embryos among the treatments. High concentrations of TDZ (0.2-2 mgl-') promoted bulblet formation, but reduced root formation. Number of shoot primordia was high with higher 2,4-D concentrations irrespective of TDZ. The highest number of bulblets (6.4) was obtained with I mgl-1 2,4-D+0.2 mgl-* TDZ.

Somatic embryogenesis and plant regeneration from barley cultivars grown in Spain

Thirty-two barley cultivars grown in Spain, 18 of the two-row type and 14 of the six-row type, were screened for plant regeneration from cultured immature embryos. Although there was much variation in regeneration capacity among the cultivars, plants were obtained from all cultivars except Almunia. No statistical differences were found in the percentage of regeneration between two- and six-row types. The influence of the auxins 2,4-dichlorophenoxyacetic acid, dicamba, and picloram on the induction and maintenance of embryogenesis and regeneration capacity after 3-4 months in culture, were evaluated for cultivars Cobra, Hop and Reinette. Hop had the highest rates of maintenance of embryogenic capacity and plant regeneration. The medium containing dicamba gave the best embryogenic callus induction, maintenance and regeneration. Five regeneration media, differing in growth regulators and micronutrient composition, as well as partial desiccation of the calli before regeneration, were tested. The regeneration medium containing 10 μM copper sulfate gave the best results. Regeneration frequencies after 3-4 months in culture of cultivar Hop were raised from 59.5 to 93.7% in this medium. Silver nitrate and partial desiccation of the calli also enhanced plant regeneration, but the medium containing 10 μM of silver nitrate reduced root formation.

Transgenic tobacco plants expressing yeast‐derived invertase in either the cytosol, vacuole or apoplast: a powerful tool for studying sucrose metabolism and sink/source interactions

In higher plants sucrose plays a central roles with respect to both short-term storage and distribution of photoassimilates formed in the leaf. Sucrose is synthesized in the cytosol, transiently stored in the vacuole and exported via the apoplast. In order to elucidate the role of the different compartments with respect to sucrose metabolism, a yeast-derived invertase was directed into the cytosol and vacuole of transgenic tobacco plants. This was in addition to the targeting of yeast-derived invertase into the apoplast described previously. Vacuolar targeting was achieved by fusing an N-terminal portion (146 amino acids long) of the vacuolar protein patatin to the coding region of the mature invertase protein. Transgenic tobacco plants expressing the yeast-derived invertase in different subcellular compartments displayed dramatic phenotypic differences when compared to wild-type plants. All transgenic plants showed stunted growth accompanied by reduced root formation. Starch and soluble sugars accumulated in leaves indicating that the distribution of sucrose was impaired in all cases. Expression of cytosolic yeast invertase resulted in the accumulation of starch and soluble sugars in both very young (sink) and older (source) leaves. The leaves were curved, indicating a more rapid cell expansion or cell division at the upper side of the leaf. Light-green sectors with reduced photosynthetic activity were evenly distributed over the leaf surface. With the apoplastic and vacuolar invertase, the phenotypical changes induced only appear in older (source) leaves. The development of bleached and/or necrotic sectors was linked to the source state of a leaf. Bleaching followed the sink to source transition, starting at the rim of the leaf and moving to the base. The bleaching was paralleled by the inhibition of photosynthesis.

The Effect of IAA on Sugar Accumulation and Basipetal Transport of 14C‐labelled Assimilates in Relation to Root Formation in Phaseolus vulgaris Cuttings

AbstractThe effect of indol‐3yl‐acetic acid on root formation, accumulation of 80% ethanol‐soluble sugars and basipetal transport of 14C‐labelled assimilates has been investigated in Phaseolus vulgaris (cv. Canadian Wonder) hypocotyl cuttings. The removal of leaves reduced root formation in the hypocotyl, while excision of the apical bud was less detrimental. The expression of the IAA effect in inducing more roots was dependent on the area of leaves, and was found to be better when all leaves were present. Sugars accumulated slowly at the base of cuttings during a four‐day period after excision, and IAA greatly enhanced this accumulation. By comparing sugar content at the base of green and starved cuttings it was established that IAA greatly increased it concurrently with root formation.IAA applied in solution to the hypocotyl greatly enhanced the basipetal transport of 14C‐labelled assimilates and their accumulation at the hypocotyl during a 24‐h period. The IAA‐induced accumulation was found to be connected with a greater mobilization of labelled assimilates from upper parts of the cutting. Experiments involving pretreatment with IAA and transport in cuttings already possessing root primordia, suggest a dual effect of IAA: (I) a direct effect on transport, and (2) an increase in the root‐“sink”. It is concluded that both may be operating in inducing basipetal accumulation of labelled assimilates. It is suggested that one of the roles of IAA in promoting rooting of cuttings is to increase sugar availability at the site of root formation.

Endogenous Sugar Levels and Their Effects on Root Formation and Petiole Yellowing of Detached Mustard Cotyledons

AbstractDetached cotyledons of Sinapis alba rooted readily in water in petri dishes in the light. The addition of (6 × 10−2M) galactose, mannose or 2‐deoxy‐D‐glucose to the culture medium proved toxic to cotyledon growth. Of the other sugars tested that were not toxic, sucrose was the most inhibitory to root formation and increased petiolar yellowing to the greatest extent. Glucose was more inhibitory than fructose which in turn increased petiolar yellowing more than methyl‐D‐glucose.Sucrose, glucose, or fructose at 6 × 10−2M in the culture medium gave rise to very substantial increases in the cotyledon petiole of reducing sugar and starch with smaller increases in sucrose. Methyl‐D‐glucose had much less effect on internal sugar levels. It was found that the higher the internal level of glucose the more rapid the rate and final extent of petiolar yellowing. In general, the degree of petiolar yellowing was inversely related to the ability of the cotyledon to root. Methyl‐D‐glucose differed from the other sugars in that it delayed and reduced root formation but had very little effect on petiolar yellowing.