Rooting Of Hypocotyl Cuttings Research Articles

Synergistic effects of plant growth retardants and IBA on the formation of adventitious roots in hypocotyl cuttings of mung bean

The synergistic effect of plant growth retardants, such as daminozide, paclobutrazol and triadimefon, and of indole-3-butyric acid (IBA) on the formation of adventitious roots in hypocotyl cuttings of mung bean was studied. The three retardants and IBA all stimulated adventitious root growth, but IBA was the most effective. However, mixtures of the retardants with IBA have proven generally more effective than IBA alone in promoting adventitious root formation. When IBA was applied to the hypocotyls one day after cutting preparation followed by the growth retardant on the second day, there were even more adventitious roots produced than if applied in the reverse order. The effectiveness of the treatments were in the order, IBA followed by growth retardant, IBA + growth retardant together, and IBA alone.

Initiation of roots on hypocotyl cuttings of Pinussylvestris, with emphasis on direct rooting, root elongation, and auxin uptake

Direct rooting of hypocotyl cuttings of Pinussylvestris L. is described and compared with rooting via wound tissue. The optimal 3-indolylbutyric acid treatment for direct rooting of Pinussylvestris hypocotyl cuttings under in vitro conditions was 1.23 mM for 24 h. This treatment resulted in 45% rooting within 3 weeks after cutting. During this period, only direct rooting was observed. Three to 4 weeks after cutting, roots developed either directly on the hypocotyl or via wound tissue. After the first month, rooting took place predominantly via wound tissue. The optimal 3-indolylbutyric acid treatment found for in vitro culture could successfully be used for hydroponic culture (under nonsterile conditions). In vitro culture inhibited root elongation. However, after transfer of rooted cuttings from in vitro to hydroponic culture, root elongation increased markedly. Uptake studies with 3-[5(n)-3H]indolylacetic acid mixed with the nutrient solution showed that auxin uptake by the cutting probably occurred mainly through uptake of the nutrient solution. After 24 h treatment with 1.43 mM 3-indolylacetic acid, the concentration taken up by the cuttings was 0.91 nmol/mg fresh weight. Differences between individual cuttings in auxin uptake could not explain the poor direct rooting of Pinussylvestris hypocotyl cuttings cultured in vitro.

Initiation and development of wound tissue and roots on hypocotyl cuttings of Pinus sylvestris in vitro

The rooting of hypocotyl cuttings from 20‐day‐old seedlings of Pinus sylvestris L. cultured in vitro is discussed. About 40% of the cuttings cultured on medium lacking activated charcoal produced roots during the first two months. When activated charcoal was added to the medium, either root formation (75% formed roots) or wound tissue growth (95% formed large wound tissues) was stimulated in different experiments. These large wound tissues did not develop any roots. The anatomical changes in the basal part of the cuttings were similar during the first two weeks in all the cuttings studied. A vascular cylinder composed of short tracheids with many pores developed. Thereafter the differentiation process became varied. The amount of wound tissue produced and the time for rooting differed among the cuttings. Tracheid nests which were in contact with the vascular system in the hypocotyl via short tracheids were observed after three weeks. Subsequently, roots developed from the tracheid nests. The longer root formation was delayed, the larger the wound tissue became.Short tracheids were found close to the wound tissue surface. Their ability to adsorb nutrients and water is discussed.

Auxin Transport Inhibitors and the Rooting of Hypocotyl Cuttings from Etiolated Mung-bean Vigna radiata (L.) Wilczek Seedlings

The auxin transport inhibitors 2, 3, 5-triiodobenzoic acid (TIBA) and naphthylphthalamic acid (NPA) inhibited adventitious root formation (ARF) induced by indol-3-butyric acid (IBA) on cuttings from etiolated mung-bean seedlings floated on solutions of the growth regulators. The concentrations of TIBA and NPA required for a 25 per cent reduction in ARF with 10 μM IBA were estimated by linear interpolation to be 11.3 μm and 0.42 μM respectively. NPA is a particularly potent inhibitor of IBA-induced ARF. The inhibitory effect of either compound was reversible by higher concentrations of IBA. NPA had no effect when applied after the auxin treatment. The inhibitory effects of TIBA or NPA could not be explained by effects on the uptake or metabolism of [2-14C]IAA. Considering this and other evidence, it is suggested that NPA and possibly TIBA are acting as specific antagonists of auxin in the induction of ARF.

Hormones are no causal links in phytochrome-mediated adventitious root formation in mustard seedlings (Sinapis alba L.)

The question of whether or not hormones are causal links in the realization of phytochrome control during photomorphogenesis was investigated using the phytochrome-dependent formation of adventitious roots in hypocotyl cuttings excised from mustard seedlings as a test system. Histological examination of regenerating "rest" seedlings revealed that phytochrome (operationally, continuous far-red light) mediates the de novo formation of root primordia in the pericycle region of the hypocotyl near the cutting surface withing 12-24 h after excision.Auxin (IAA), gibberellin (GA3), Cytokinin (kinetin), abscisic acid (ABA), and ethylene had no promotive effect on primordium formation in dark-grown or far-red irradiated rest seedlings. Depending on concentration, the application of these hormones was either ineffective or inhibitory in the rooting response. It is concluded that phytochrome does not operate through changes of hormone (auxin, gibberellin, cytokinin, ABA, ethylene) levels.While externally applied ethylene had no specific effect on primordium formation, the number of primordia produced in darkness could be increased to the far-red light level by removing the endogenously formed ethylene. Since the stimulatory effect of light could not be related to a lower ethylene level, it is concluded that ethylene interferes with primordium formation by modulating the susceptibility of this process to phytochrome control. This ethylene effect takes place in a concentration range below the range that can be manipulated by external application of the hormone.

Stimulatory Effect of Purine and Pyrimidine Bases and their Role in the Mediation of Auxin Action through the Regulation of Carbohydrate Metabolism during Adventitious Root Formation in Hypocotyl Cuttings of Phaseolus mungo

Summary Exogenous application of purine and pyrimidine bases in combination with auxin and sucrose hastened and enhanced the production of roots in hypocotyl cuttings of Phaseolus mungo. The changes in the biochemical drifts in dry matter, carbohydrates, amylase and invertase at different stages of root formation show that: Dry matter content of cuttings increased in sucrose as well as IAA + Suc without or with base after 12hr but remained low in water, IAA and base alone till 48hr synchronising with an increase in carbohydrate content at 18hr in IAA + Suc with or without a base as well as in sucrose alone. The amylase activity increased in all the cultures during 12-24 hr while the invertase activity increased during 6-12 hr to decline subsequently to increase again at 24 hr. The significance of these enzymes in relation to nitrogenous bases on the differentiation of cainbial derivatives into roots has been discussed.

Effect of Ethrel on the Rooting of Mung Bean Hypocotyl Cuttings

Summary Ethrel promoted the rooting of hypocotyl cuttings of mung bean synergistically with IAA. TIBA inhibited rooting. The inhibition was enhanced by both IAA and ethrel used singly but was partially relieved when used in combination. Ethrel and IAA in combination also removed the inhibition caused by GAa more effectively than with either of them alone. Cuttings taken from young seedlings or seedlings grown in dark or defoliated did not respond synergistically to ethrel and IAA.