Plant Development

Plants deploy a finely tuned balance between growth and defence responses for better fitness. Crosstalk between defence signalling hormones such as salicylic acid (SA) and jasmonates (JAs) as well as growth regulators plays a significant role in mediating the trade-off between growth and defence in plants. Here, we specifically discuss how the mutual antagonism between the signalling of auxin and SA impacts on plant growth and defence. Furthermore, the synergism between auxin and JA benefits a class of plant pathogens. JA signalling also poses growth cuts through auxin. We discuss how the effect of cytokinins (CKs) is multifaceted and is effective against a broad range of pathogens in mediating immunity. The synergism between CKs and SA promotes defence against biotrophs. Reciprocally, SA inhibits CK-mediated growth responses. Recent reports show that CKs promote JA responses; however, in a feedback loop, JA suppresses CK responses. We also highlight crosstalk between auxin and CKs ...

We evaluated the potential of chitosan both to stimulate plant development and to induce protection from Botrytis cinerea in Vitis vinifera L. plantlets. The presence of 1.75% (v/v) chitogel in the culture medium was the optimal concentration for in vitro grapevine plantlet growth, as determined by measurements on enhancement of root and shoot biomass. Photosynthesis and related parameters were also stimulated in chitogel-treated plantlets. Chitogel reduced the development of Botrytis cinerea and induced cytological alterations to the pathogen. When challenged with the fungus, a significant decrease in disease incidence was observed in plants growing on medium supplemented with chitogel. Furthermore, exogenous foliar applications of chitogel to plantlets growing on chitogel-free medium sensitized them so as to be protected against Botrytis cinerea attack. Our results indicate that chitogel can be used in the vineyard as a means to attain protection against Botrytis cinerea and that its application may counteract the wide use of chemical pesticides.

The combination of UV irradiation and hydrogen peroxide (UV–H2O2) was shown to be effective in treating water spiked with 2,2′,4,4′,5,5′-hexachlorobipheny (PCB 153), reducing its concentration by as much as 98%. To test the toxicity of the effluent, bioassays involving three species of primary producers were performed. Results showed the effluent exerting an adverse effect on the algae Scenedesmus bijugatus and

Eleven allelochemicals (ferulic acid, cinnamic acid, 4-hydroxybenzoic acid, hydroxycinnamic acid, methyl propionate, oxalic acid, methylmalonic acid, p-anisic acid, butyric acid, 3-hydroxybutyric acid, and azulene) were identified in the exudate of Cistus ladanifer L. We studied the effect of each on germination, cotyledon emergence, root length, and cotyledon length of Rumex crispus. Three groups were distinguished with respect to phytotoxic activity: compounds with low activity (ferulic acid, 4-hydroxybenzoic acid, oxalic acid, methylmalonic acid, p-anisic acid, hydroxybutyric acid, and azulene), with intermediate activity (cinnamic acid and hydroxycinnamic acid), and with high activity (methyl propionate and butyric acid). The effect of the interaction of the compounds was studied. When acting conjointly, all combinations tested produced a more negative effect on both germination and seedling growth than when acting alone. The interaction affected cotyledon emergence and root length more negatively than germination and cotyledon length. When hydroxycinnamic acid and cinnamic acid were added to these mixtures there was an enhancement in the phytotoxic activity, accentuating the effect of the other allelochemicals.

Extensive communication occurs between plants and microorganisms during different stages of plant development in which signaling molecules from the two partners play an important role. Volatile organic compounds (VOCs) emission by certain plant-growth promoting rhizobacteria (PGPR) has been found to be involved in plant growth. However, little is known about the role of bacterial VOCs in plant developmental processes. In this work, we investigated the effects of inoculation with twelve bacterial strains isolated from the rhizosphere of lemon plants (Citrus aurantifolia) on growth and development of Arabidopsis thaliana seedlings. Several bacterial strains showed a plant growth promoting effect stimulating biomass production, which was related to differential modulation of root-system architecture. The isolates L263, L266, and L272a stimulated primary root growth and lateral root development, while L254, L265a and L265b did not significantly alter primary root growth but strongly promoted lateral root formation. VOC emission analysis by SPME-GC-MS identified aldehydes, ketones and alcohols as the most abundant compounds common to most rhizobacteria. Other VOCs, including 1-octen-3-ol and butyrolactone were strain specific. Characterization of L254, L266 and L272a bacterial isolates by 16S rDNA analysis revealed the identity of these strains as Bacillus cereus, Bacillus simplex and Bacillus sp, respectively. Taken together, our data suggest that rhizospheric bacterial strains can modulate both plant growth promotion and root-system architecture by differential VOC emission.

Programmed cell death (PCD) or apoptosis is a genetically programmed cellular process. Though in the plant, a true caspase system is lacking, still PCD can occur throughout the life cycle at any cell type, tissue, and organ part in response to a wide range of stimuli. Here we have discussed the current understanding of plant PDC in terms of different pathways, cellular dysfunction, regulation, and signaling mechanisms. Our present study discussed how and to what extent PCD is involved in pre-zygotic and post-zygotic plant life cycle and emphasized to what extent PDC modulated in response to abiotic and biotic stress. Additionally, the expression profile of different PCD-associated genes are modulated by developmental stage, biotic-abiotic stress, cellular metabolites are elucidated. Hence, this study will be helpful for understanding the molecular and structural instincts of PDC in different stages of plant growth and development, response to biotic/abiotic stimuli, and cellular dysfunction.

The aim of this study was to investigate both a mass in vitro propagation system and the β-ecdysone content in roots and aerial parts of Pfaffia glomerata and Pfaffia tuberosa. Nodal segments of two genotypes (BRA and JB-UFSM) of P. glomerata, originated from aseptically grown plants, were cultivated on hormone-free Murashige and Skoog medium. For the proliferation of P. tuberosa shoots, nodal segments, originated from aseptically grown plants, were either cultivated on hormone-free Murashige and Skoog (MS) medium or were supplemented with 1.0 µM thidiazuron (TDZ); the elongation and rooting of these plants were carried out on MS medium without TDZ. Plantlets of both species were acclimatized and transferred to field conditions. The β-ecdysone content in the plants was determined by high performance liquid chromatography. The BRA genotype showed a greater in vitro proliferation rate and β-ecdysone content than that of the JB-UFSM genotype. The culture of nodal segments of P. tuberosa on medium with 1.0 µM TDZ with subsequent subcultivation of shoots on hormone-free medium was shown to be a suitable method for micropropagation due to the high multiplication rate and good plant development. Both species showed good adaptation to ex vitro conditions. The β-ecdysone content in micropropagated P. tuberosa was similar to that found in field-grown plants. For both species, the aerial parts accumulated higher β-ecdysone content than roots. These results reveal that micropropagation is a successful, alternative method for rapid plant multiplication of both species of Brazilian ginseng. Furthermore, this study demonstrates that these two species have a potential for cultivation that is associated with high β-ecdysone production.

The tritrophic interactions between plants, herbivores and avian predators are complex and prone to trophic cascades. We conducted a meta-analysis of original articles that have studied birds as predators of invertebrate herbivores, to compare top-down trophic cascades with different plant responses from different environments and climatic areas. Our search found 29 suitable articles, with a total of 81 separate experimental study set-ups. The meta-analysis revealed that plants benefited from the presence of birds. A significant reduction was observed in the level of leaf damage and plant mortality. The presence of birds also positively affected the amount of plant biomass, whereas effects on plant growth were negligible. There were no differences in the effects between agricultural and natural environments. Similarly, plants performed better in all climatic areas (tropical, temperate and boreal) when birds were present. Moreover, both mature plants and saplings gained benefits from the presence of birds. Our results show that birds cause top-down trophic cascades and thus they play an integral role in ecosystems.

The plant hormone auxin is secreted in root apices via phospholipase Dzeta2 (PLDzeta2) activity which produces specific population of phosphatidic acid that stimulates secretion of vesicles enriched with auxin. These vesicles were reported to be localized at plant synapses which are active in auxin secretion, especially at the transition zone of the root apex. There are several implications of this vesicular secretion of auxin. In root apices, auxin emerges as plant neurotransmitter-like signal molecule which coordinates activities of adjacent cells via electric and chemical signaling. Putative quantal release of auxin after electrical stimulation, if confirmed, would be part of neuronal communication between plant cells. As auxin transport across plant synapses is tightly linked with integrated sensory perception of environment, especially of omnipresent gravity and light, this process is proposed to mediate the plant perception of environment. These neuronal features allow sessile...