S.M.P. Carvalho

Avoiding high relative air humidity during critical stages of leaf ontogeny is decisive for stomatal functioning

Plants of several species, if grown at high relative air humidity (RH ≥85%), develop stomata that fail to close fully in case of low leaf water potential. We studied the effect of a reciprocal change in RH, at different stages of leaf expansion of Rosa hybrida grown at moderate (60%) or high (95%) RH, on the stomatal closing ability. This was assessed by measuring the leaf transpiration rate in response to desiccation once the leaves had fully expanded. For leaves that started expanding at high RH but completed their expansion after transfer to moderate RH, the earlier this switch took place the better the stomatal functioning. Leaves initially expanding at moderate RH and transferred to high RH exhibited poor stomatal functioning, even when this transfer occurred very late during leaf expansion. Applying a daily abscisic acid (ABA) solution to the leaves of plants grown at continuous high RH was effective in inducing stomatal closure at low water potential, if done before full leaf expansion (FLE). After FLE, stomatal functioning was no longer affected either by the RH or ABA level. The results indicate that the degree of stomatal adaptation depends on both the timing and duration of exposure to high RH. It is concluded that stomatal functionality is strongly dependent on the humidity at which the leaf completed its expansion. The data also show that the effect of ambient RH and the alleviating role of ABA are restricted to the period of leaf expansion.

Influence of greenhouse climate and plant density on external quality of chrysanthemum (Dendranthema grandiflorum (Ramat.) Kitamura): First steps towards a quality model

Summary The effects of greenhouse climate and plant density on external quality of chrysanthemum (Dendranthema grandiflorum syn. Chrysanthemum morifolium) are reviewed. The external quality aspects analysed in this paper are stem morphology (length, diameter and “strength”), leaf morphology (number and size) and floweringaspects (number, size and position). Increasing assimilate availability level (e.g. higher light intensity, higher CO2 concentration and/or lower plant density) has a positive effect on several external quality aspects of chrysanthemum. It results in longer stems, more lateral branches, a higher number of flowers and increased flower size per plant. Furthermore, both temperature and daily light integral are the main factors that determine stem elongation and time toflowering. Time to flowering is not affected by the CO2level. In general it can be concluded that eachexternal quality character is influenced by several growing conditions interacting with each other. Therefore, the development of an explanatory model, as a climate control tool to predict and optimize external quality in year-round chrysanthemumproduction, would be of utmost importance. To build such a model detailed and integrated information about chrysanthemum growth and development is needed. This review intends to serve as a starting point for modelling external quality of cut chrysanthemum.

Effect of assimilate availability on flower characteristics and plant height of cut chrysanthemum: an integrated study

Summary The influence of assimilate availability on the number of flowers per plant, individual flower size and plant height of chrysanthemum was investigated in different seasons, integrating the results from eight greenhouse experiments. Increased assimilate availability was obtained by higher light intensity, higher CO2 concentration, lower plant density or longer duration of the long-day (LD) period. Within each experiment, conditions that were expected to increase assimilate availability indeed resulted in higher total dry mass of the plant, excluding roots (TDMp). In contrast, flower mass ratio was hardly affected, except for the increased duration of the LD period that signi®cantly reduced the partitioning towards the flowers. Consequently, an increase in total flower dry mass with assimilate availability was observed and this was mainly a result of higher numbers of flowers per plant, including flower buds (NoF). Individual flower size was only influenced by assimilate availability when average daily incident PAR during short-day period was lower than 7.5 mol m–2 d–1, resulting in lighter and smaller flowers. Excluding the positive linear effect of the duration of the LD period, assimilate availability hardly influenced plant height (<10% increase). It is concluded that within a wide range of growth conditions chrysanthemum invests additional assimilates, diverted to the generative organs, in increasing NoF rather than in increasing flower size. Irrespective of the growth conditions and season a positive linear relationship (r2 = 0.90) between NoF and TDMp was observed. This relationship was cultivar-specific. The generic nature of the results is discussed.

Temperature affects Chrysanthemum flower characteristics differently during three phases of the cultivation period

Summary The sensitivity to temperature of the number of flowers per plant including flower buds (NFPP), flower size, position and colour was investigated in cut chrysanthemum (Chrysanthemum morifolium cv. ‘Reagan Improved’). Plants were grown either in a glasshouse at constant 24 h mean temperatures throughout cultivation (17°C or 21°C), or in growth chambers at 32 different temperature combinations (from 15°C to 24°C). The latter temperature combinations were applied by dividing the cultivation period into three sequential phases: long-day period (phase I), start of short-day period to visible terminal flower bud (phase II), and end of phase II to harvest stage (phase III). All flower characteristics were affected significantly by temperature, except for flower position within the plant. Higher temperatures increased NFPP, mainly by increasing the number of flower buds, but decreased individual flower size. The temperature effect was also dependent on the phase of the cultivation period. In general, flower characteristics were less sensitive to temperature applied during the long-day period. NFPP was affected positively by temperature, mainly during phase III, whereas individual flower size increased with temperature during phase II, but decreased with temperature during phase III. Lower temperatures during phase III significantly enhanced flower colour intensity. Interest in using a more dynamic heating strategy is discussed.

A virtual plant that responds to the environment like a real one: the case for chrysanthemum

• Plants respond to environmental change through alterations in organ size, number and biomass. However, different phenotypes are rarely integrated in a single model, and the prediction of plant responses to environmental conditions is challenging. The aim of this study was to simulate and predict plant phenotypic plasticity in development and growth using an organ-level functional-structural plant model, GreenLab. • Chrysanthemum plants were grown in climate chambers in 16 different environmental regimes: four different temperatures (15, 18, 21 and 24°C) combined with four different light intensities (40%, 51%, 65% and 100%, where 100% is 340 μmol m⁻² s⁻¹). Measurements included plant height, flower number and major organ dry mass (main and side-shoot stems, main and side-shoot leaves and flowers). To describe the basipetal flowering sequence, a position-dependent growth delay function was introduced into the model. • The model was calibrated on eight treatments. It was capable of simulating multiple plant phenotypes (flower number, organ biomass, plant height) with visual output. Furthermore, it predicted well the phenotypes of the other eight treatments (validation) through parameter interpolation. • This model could potentially serve to bridge models of different scales, and to link energy input to crop output in glasshouses.

Elevated air movement enhances stomatal sensitivity to abscisic acid in leaves developed at high relative air humidity

High relative air humidity (RH ≥ 85%) during growth leads to stomata malfunctioning, resulting in water stress when plants are transferred to conditions of high evaporative demand. In this study, we hypothesized that an elevated air movement (MOV) 24 h per day, during the whole period of leaf development would increase abscisic acid concentration ([ABA]) enhancing stomatal functioning. Pot rose ‘Toril’ was grown at moderate (61%) or high (92%) RH combined with a continuous low (0.08 m s-1) or high (0.92 m s-1) MOV. High MOV reduced stomatal pore length and aperture in plants developed at high RH. Moreover, stomatal function improved when high MOV-treated plants were subjected to leaflet desiccation and ABA feeding. Endogenous concentration of ABA and its metabolites in the leaves was reduced by 35% in high RH, but contrary to our hypothesis this concentration was not significantly affected by high MOV. Interestingly, in detached leaflets grown at high RH, high MOV increased stomatal sensitivity to ABA since the amount of exogenous ABA required to decrease the transpiration rate was significantly reduced. This is the first study to show that high MOV increases stomatal functionality in leaves developed at high RH by reducing the stomatal pore length and aperture and enhancing stomatal sensitivity to ABA rather than increasing leaf [ABA].

High relative air humidity influences mineral accumulation and growth in iron deficient soybean plants.

Iron (Fe) deficiency chlorosis (IDC) in soybean results in severe yield losses. Cultivar selection is the most commonly used strategy to avoid IDC but there is a clear interaction between genotype and the environment; therefore, the search for quick and reliable tools to control this nutrient deficiency is essential. Several studies showed that relative humidity (RH) may influence the long distance transport of mineral elements and the nutrient status of plants. Thus, we decided to analyze the response of an “Fe-efficient” (EF) and an “Fe-inefficient” (INF) soybean accession grown under Fe-sufficient and deficient conditions under low (60%) and high (90%) RH, evaluating morphological, and physiological parameters. Furthermore, the mineral content of different plant organs was analyzed. Our results showed beneficial effects of high RH in alleviating IDC symptoms as seen by increased SPAD values, higher plant dry weight (DW), increased plant height, root length, and leaf area. This positive effect of RH in reducing IDC symptoms was more pronounced in the EF accession. Also, Fe content in the different plant organs of the EF accession grown under deficient conditions increased with RH. The lower partitioning of Fe to roots and stems of the EF accessions relative to dry matter also supported our hypothesis, suggesting a greater capacity of this accession in Fe translocation to the aerial parts under Fe deficient conditions, when grown under high RH.

Effect of tris(3-hydroxy-4-pyridinonate) iron(III) complexes on iron uptake and storage in soybean (Glycine max L.).

Iron deficiency chlorosis (IDC) is a serious environmental problem affecting the growth of several crops in the world. The application of synthetic Fe(III) chelates is still one of the most common measures to correct IDC and the search for more effective Fe chelates remains an important issue. Herein, we propose a tris(3-hydroxy-4-pyridinonate) iron(III) complex, Fe(mpp)3, as an IDC corrector. Different morphological, biochemical and molecular parameters were assessed as a first step towards understanding its mode of action, compared with that of the commercial fertilizer FeEDDHA. Plants treated with the pyridinone iron(III) complexes were significantly greener and had increased biomass. The total Fe content was measured using ICP-OES and plants treated with pyridinone complexes accumulated about 50% more Fe than those treated with the commercial chelate. In particular, plants supplied with compound Fe(mpp)3 were able to translocate iron from the roots to the shoots and did not elicit the expression of the Fe-stress related genes FRO2 and IRT1. These results suggest that 3,4-HPO iron(III) chelates could be a potential new class of plant fertilizing agents.

Iron partitioning at an early growth stage impacts iron deficiency responses in soybean plants (Glycine max L.)

Iron (Fe) deficiency chlorosis (IDC) leads to leaf yellowing, stunted growth and drastic yield losses. Plants have been differentiated into ‘Fe-efficient’ (EF) if they resist to IDC and ‘Fe-inefficient’ (IN) if they do not, but the reasons for this contrasting efficiency remain elusive. We grew EF and IN soybean plants under Fe deficient and Fe sufficient conditions and evaluated if gene expression and the ability to partition Fe could be related to IDC efficiency. At an early growth stage, Fe-efficiency was associated with higher chlorophyll content, but Fe reductase activity was low under Fe-deficiency for EF and IN plants. The removal of the unifoliate leaves alleviated IDC symptoms, increased shoot:root ratio, and trifoliate leaf area. EF plants were able to translocate Fe to the aboveground plant organs, whereas the IN plants accumulated more Fe in the roots. FRO2-like gene expression was low in the roots; IRT1-like expression was higher in the shoots; and ferritin was highly expressed in the roots of the IN plants. The efficiency trait is linked to Fe partitioning and the up-regulation of Fe-storage related genes could interfere with this key process. This work provides new insights into the importance of mineral partitioning among different plant organs at an early growth stage.

Alcohol use in adolescence: 5 years admissions at a pediatric emergency department

Abstract Objective To characterize the profile and pattern of alcohol consumption in adolescents, admitted with acute alcoholic intoxication (AAI) at a pediatric emergency department of North Portugal. Methods Retrospective descriptive study of adolescents aged between 10 and 17 years, admitted with AAI between 2012 and 2016. The following variables were evaluated: age, gender, drinking context, quantity and type of alcohol, Glasgow Coma Scale (GCS), previous episodes, associated injuries, transport to the emergency department, other drug consumption, blood alcohol level (BAL), blood glucose level, treatment and orientation. The χ2/Fisher’s exact test and t-Student test were performed (p < 0.05). Results A total of 180 adolescents with AAI presented. The majority of adolescents were older than 15 years old (71%) and 3% were younger than 14 years old. The mean age was 15.9 years [standard deviation (SD) 1.1 years] and 65% were males. The most common type of alcohol consumed was distilled drinks (60%). Recurrent alcohol use was identified in 7% and binge drinking was reported in 37% of patients. The mean BAL was 1.58 g/L (SD 0.6 g/L) and there were other drug consumptions (mainly cannabinoids) observed in 11% of patients. After emergency department discharge, 17% were followed at hospital consultation. There was no significant difference between boys and girls or between BAL and injuries or other drugs consumption. Conclusion This study confirms a high rate of alcohol use among adolescents, in particular “heavy episodic drinking”, revealing an easy access to alcohol at this age. The integration of alcohol use prevention programs in community and education systems should be encouraged and implemented in every adolescent consultation.