Plant physiology

About: Plant physiology is a research topic. Over the lifetime, 1537 publications have been published within this topic receiving 72038 citations.

Mineralisation of plant nitrogen following alternate wet and dry conditions

Abstract: The influence of soil drying in enhancing the mineralisation of organic nitrogen in humus raises the question as to whether, during the decomposition of plant residues, mineralisation of nitrogen is similarly affected. In studying nitrogen mineralisation during plant decomposition the material is usually left in contact with moist soil for a given period and the analyses then carried out. The object of the following experiment was to follow the course of nitrogen mineralisation during the decomposition of different plant materials and to compare the results with those obtained when decomposition was interrupted by one, two and three dry periods followed in each instance by restoration of moist conditions. It was found that intermittent drying enhanced the amount of mineral nitrogen produced, the implications of which are discussed later.

The tomato CAROTENOID CLEAVAGE DIOXYGENASE8 (SlCCD8) regulates rhizosphere signaling, plant architecture and affects reproductive development through strigolactone biosynthesis

Abstract: Summary � Strigolactones are plant hormones that regulate both above- and belowground plant architecture. Strigolactones were initially identified as rhizosphere signaling molecules. In the present work, the tomato (Solanum lycopersicum)CAROTENOID CLEAVAGE DIOXYGENASE 8 (SlCCD8) was cloned and its role in rhizosphere signaling and plant physiology assessed by generating knock-down lines. � Transgenic SlCCD8 plants were generated by RNAi-mediated silencing. Lines with different levels of strigolactone reduction – confirmed by UPLC-MS/MS – were selected and their phenotypes investigated. � Lines exhibiting reduced SlCCD8 levels displayed increased shoot branching, reduced plant height, increased number of nodes and excessive adventitious root development. In addition, theselinesexhibitedreproductivephenotypessuchassmallerflowers,fruits,aswellasfewerand smaller seeds per fruit. Furthermore, we show that strigolactone loading to the xylem sap is possibly restricted to orobanchol. � Infestation by Phelipanche ramosa was reduced by 90% in lines with a relatively mild reduction in strigolactone biosynthesis and secretion while arbuscular mycorrhizal symbiosis, apical dominance and fruit yield were only mildly affected. This demonstrates that reduction of strigolactone biosynthesis could be a suitable tool in parasitic weed management. Furthermore, ourresultssuggestthatstrigolactones areinvolvedinevenmorephysiologicalprocessesthanso far assumed.

Alfalfa plant-derived biostimulant stimulate short-term growth of salt stressed Zea mays L. plants

Abstract: The effects of an alfalfa plant (Medicago sativa L.) hydrolysate-based biostimulant (EM) containing triacontanol (TRIA) and indole-3-acetic acid (IAA) were tested in salt-stressed maize plants. Plants were grown for 2 weeks in the absence of NaCl or in the presence (25, 75 and 150 mM). On the 12th day, plants were supplied for 48 h with 1.0 mg L−1 EM or 11.2 μM TRIA. EM and TRIA stimulated the growth and nitrogen assimilation of control plants to a similar degree, while NaCl reduced plant growth, SPAD index and protein content. EM or TRIA increased plant biomass under salinity conditions. Furthermore, EM induced the activity of enzymes functioning in nitrogen metabolism. The activity of antioxidant enzymes and the synthesis of phenolics were induced by salinity, but decreased after EM treatment. The enhancement of phenylalanine ammonia-lyase (PAL) activity and gene expression by EM was consistent with the increase of flavonoids. The present study proves that the EM increases plant biomass even when plants are grown under salinity conditions. This was likely because EM stimulated plant nitrogen metabolism and antioxidant systems. Therefore, EM may be proposed as bioactive product in agriculture to help plants overcome stress situations.

The Role of Tobacco Aquaporin1 in Improving Water Use Efficiency, Hydraulic Conductivity, and Yield Production Under Salt Stress

Abstract: Tobacco (Nicotiana tabacum; C3) plants increase their water use efficiency (WUE) under abiotic stress and are suggested to show characteristics of C4 photosynthesis in stems, petioles, and transmitting tract cells. The tobacco stress-induced Aquaporin1 (NtAQP1) functions as both water and CO(2) channel. In tobacco plants, overexpression of NtAQP1 increases leaf net photosynthesis (A(N)), mesophyll CO(2) conductance, and stomatal conductance, whereas its silencing reduces root hydraulic conductivity (L(p)). Nevertheless, interaction between NtAQP1 leaf and root activities and its impact on plant WUE and productivity under normal and stress conditions have never been suggested. Thus, the aim of this study was to suggest a role for NtAQP1 in plant WUE, stress resistance, and productivity. Expressing NtAQP1 in tomato (Solanum lycopersicum) plants (TOM-NtAQP1) resulted in higher stomatal conductance, whole-plant transpiration, and A(N) under all conditions tested. In contrast to controls, where, under salt stress, L(p) decreased more than 3-fold, TOM-NtAQP1 plants, similar to maize (Zea mays; C4) plants, did not reduce L(p) dramatically (only by approximately 40%). Reciprocal grafting provided novel evidence for NtAQP1's role in preventing hydraulic failure and maintaining the whole-plant transpiration rate. Our results revealed independent, albeit closely related, NtAQP1 activities in roots and leaves. This dual activity, which increases the plant's water use and A(N) under optimal and stress conditions, resulted in improved WUE. Consequently, it contributed to the plant's stress resistance in terms of yield production under all tested conditions, as demonstrated in both tomato and Arabidopsis (Arabidopsis thaliana) plants constitutively expressing NtAQP1. The putative involvement of NtAQP1 in tobacco's C4-like photosynthesis characteristics is discussed.

Sucrose transporter StSUT4 from potato affects flowering, tuberization, and shade avoidance response

Abstract: Sucrose (Suc) transporters belong to a large gene family. The physiological role of SUT1 proteins has been intensively investigated in higher plants, whereas that of SUT4 proteins is so far unknown. All three known Suc transporters from potato (Solanum tuberosum), SUT1, SUT2, and SUT4, are colocalized and their RNA levels not only follow a diurnal rhythm, but also oscillate in constant light. Here, we examined the physiological effects of transgenic potato plants on RNA interference (RNAi)-inactivated StSUT4 expression. The phenotype of StSUT4-RNAi plants includes early flowering, higher tuber production, and reduced sensitivity toward light enriched in far-red wavelength (i.e. in canopy shade). Inhibition of StSUT4 led to tuber production of the strict photoperiodic potato subsp. andigena even under noninductive long-day conditions. Accumulation of soluble sugars and Suc efflux from leaves of transgenic plants are modified in StSUT4-RNAi plants, leading to modified Suc levels in sink organs. StSUT4 expression of wild-type plants is induced by gibberellins and ethephon, and external supply of gibberellic acid leads to even more pronounced differences between wild-type and StSUT4-RNAi plants regarding tuber yield and internode elongation, indicating a reciprocal regulation of StSUT4 and gibberellins.