Fig 2 - uploaded by Abraham J Escobar-Gutiérrez
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Sch ́ma d’un pied de ma ̈s ` la floraison et num ́rotation des feuilles. La feuille terminale, ici de rang 16 (F16), est not ́e FT; sur certains pieds, la FT ́tait de rang 15 au cours de l’ ́tude. Chaque m ́tam `re comprend un entrenœud de la tige, un nœud, une feuille (gaine et limbe s ́par ́s par la ligule) partant du nœud situ ́ au sommet de l’entrenœud et un axe secondaire partant de la base de l’entrenœud, se d ́veloppant (ou non) en ́pi. Dans l’encart de droite, le sch ́ma d ́velopp ́ des entrenœuds 11, 12 et 13 pr ́cise leur relation avec l’ ́pi (seul le bas des trois feuilles est repr ́sent ́, comprenant la gaine et la base du limbe; la ligule est figur ́e par une ligne en pointill ́).
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In monocarpic species such as corn, senescence of leaves is coordinated with that of the whole plant and influenced by the reproductive function. The objective of the present study was to describe the evolution of corn senescence along two axes: (1) the whole-plant axis, where all foliar stages were each considered as an entity, and (2) the foliar...
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Context 1
... le temps sera exprimé en sommes des températures journalières moyennes de croissance (ou degrés-jours de croissance) depuis le semis, avec un seuil de 6 8C selon les préconisations de l'Association générale des producteurs de maı¨smaı¨s (1987) pour le maı¨smaı¨s 'Déa'. La numérotation des feuilles et la géométrie d'un pied de maı¨smaı¨s adulte ( fig. 2 et tableau 1) ainsi que la méthode d'estimation de la surface foliaire verte a ` partir de la forme des feuilles et de leur « longueur verte » ont e ´té décrites précisément par Combe (2005). Deux séries de mesures ont e ´té effectuées a ` partir de la floraison (sortie des soies sur 50 % des e ´pis) jusqu'a ` la récolte, 10 semaines ...
Context 2
... de sénescence, me- surée par l'indice de décoloration du limbe (proportion de la longueur décolorée sur la longueur totale) de chaque feuille au cours de la saison de végétation, a e ´té e ´tudiée dans un Mesures préliminaires de variation moyenne des teneurs en eau et en matière sèche de feuilles de rang 11 (F11) sous e ´pi de maı¨smaı¨s (voir fig. 2), le long des limbes et des nervures centrales, lesquels ont e ´té découpés en cinq zones (z1-z5) a ` différentes heures (quatre pré- lèvements de quatre limbes chacun) au cours d'une journée. Les mesures ont e ´té effectuées immédiatement après les prélèvements, sauf pour celui de 11:00 pour lequel les mesures ont eu lieu a ` 12:00. ...
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... chaque date de prélèvement des limbes, la concor- dance des dimensions (hauteur du sommet de la ligule sur Mesures préliminaires de l'effet de l'heure de la journée sur la teneur en chlorophylle de feuilles de rang 11 (F11) sous e ´pi de maı¨smaı¨s (voir fig. 2), le long des limbes, lesquels ont e ´té découpés en cinq zones (z1-z5) a ` différentes heures (quatre prélèvements de quatre limbes chacun) au cours d'une journée. Les mesures ont e ´té effectuées immédiatement après les prélèvements, sauf pour celui de 11:00 pour lequel les mesures ont eu lieu a ` 12:00. Les tracés continus ...
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... al. 2003). A ` une e ´chelle macroscopique, nous avons observé des gradients de teneurs surfaciques en eau et en matière sèche entre la pointe et la base des limbes pour certains rangs ( fig. 6A et 6B). Les teneurs en eau et en matière sèche le long des nervures diminuent de façon plus marquée mais plus irrégulière que dans le reste du limbe (ta- bleaux 2 et 3, fig. 7). La décoloration associée a ` la sénes- cence débute par la pointe de la feuille et se poursuit vers la ligule, quel que soit le rang de la feuille (Combe 2005). Toutefois, même si visuellement le changement de couleur du vert au jaune sec est relativement net (la zone intermé- diaire, jaune vert, est large de 1 a ` 2 cm (Combe ...
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... feuilles 10, 11 et 12 ont le port le plus horizontal (Si- noquet et Bonhomme 1989) et nos résultats confirment qu'elles ont aussi la plus grande surface de limbe ( fig. 2 et tableau 1), projetant ainsi le maximum d'ombre sur les feuil- les inférieures. Inversement, les feuilles du sommet, avec une surface de limbe plus petite et un port plus dressé, jet- tent relativement peu d'ombre sur les feuilles situées en des- sous, ce qui pourrait expliquer la sénescence plus tardive des feuilles 12 et 13. La ...
Citations
... Additionally, the maximum ANT values were reached at 30 DAA for both WCs, although they were higher in WS. These values indicate that leaf senescence was accelerated and influenced by the water-limited environment [56]. Similarly, the FLV values, like the ANT, were always higher in the WS conditions, demonstrating the effect of water limitation in increasing these substances. ...
... The conclusion is that soil water limitation, regardless of the genotype groups, reduced the greenness index more quickly in WS. The plant reproductive stage coordinates leaf senescence but is also strongly affected by the environment [56]. The SPAD readings serve as an indicator of photochemical activity, as they exhibit a strong positive correlation with the leaf chlorophyll concentration, providing insights into the photosynthetic activity [57]. ...
Water stress can lead to physiological and morphological damage, affecting the growth and development of popcorn. The objective of this study was to identify the yield potential of 43 popcorn lines derived from a Latin American germplasm collection, based on agronomic and physiological traits, under full irrigation (WW) and water deficit conditions (WS), aiming to select superior germplasm. The evaluated agronomic traits included the ear length and diameter, number of grains per row (NGR) and rows per ear (NRE), grain yield (GY), popping expansion (EC), volume of expanded popcorn per hectare (VP), grain length (GL), width, and thickness. The physiological traits included the chlorophyll, anthocyanin, and flavonoid content in the leaves. The genetic variability and distinct behavior among the lines for all the agronomic traits under WW and WS conditions were observed. When comparing the water conditions, line L292 had the highest mean for the GY, and line L688 had the highest mean for the EC, highlighting them as the most drought-tolerant lines. A water deficit reduced the leaf greenness but increased the anthocyanin content as an adap-tive response. The GY trait showed positive correlations with the VP, NGR, and GL under both water conditions, making the latter useful for indirect selection and thus of great interest for plant breeding targeting the simultaneous improvement of these traits.
... Leaf senescence is governed by the different phenological stages of plants but is also strongly influenced by the environment [44]-in particular, by water restriction. Both at the leaf level-measured by the SPAD index-and the canopy level-measured by the NDVI-leaf senescence occurred earlier in the genotypes evaluated under WS. ...
The identification of traits associated with drought tolerance in popcorn is a contribution
to support selection of superior plants under soil water deficit. The objective of this study was to choose morphological traits and the leaf greenness index, measured on different dates, to estimate grain yield (GY) and popping expansion (PE), evaluated in a set of 20 popcorn lines with different genealogies, estimated by multiple regression models. The variables were divided into three groups: morpho-agronomic traits—100-grain weight (GW), prolificacy (PR), tassel length (TL), number of tassel branches, anthesis-silking interval, leaf angle (FA) and leaf rolling (FB); variables related to theintensity of leaf greenness during the grain-filling period, at the leaf level, measured by a portablechlorophyll meter (SPAD) and at the canopy level, calculated as the normalized difference vegetation index (NDVI). The inbred lines were cultivated under two water conditions: well-watered (WW), maintained at field capacity, and water stress (WS), for which irrigation was stopped before male flowering. The traits GY (55%) and PE (28%) were most affected by water restriction. Among the morpho-agronomic traits, GW and PR were markedly reduced (>10%). Under dry conditions, the FA in relation to the plant stalk tended to be wider, the FB curvature greater and leaf senescence accelerated (>15% at 22 days after male flowering). The use of multiple regression for the selection of predictive traits proved to be a useful tool for the identification of groups of adequate traits to efficiently predict the economically most important features of popcorn (GY and PE). The SPAD index measured 17 days after male flowering proved useful to select indirectly for GY, while, among the morphological traits, TL stood out for the same purpose. Of all traits, PR was most strongly related with PE under WS, indicating its use in breeding programs. The exploitation of these traits by indirect selection is expected to induce increments in GY and PE.
... Moreover, SPAD index decreases faster under WS conditions [13,23,24], because the leaf senescence occurs more sharply under WS in comparison with the WW condition. The foliar senescence is coordinated by reproductive plant stadium, but also strongly influenced by the environment [44]. Thus, SPAD index is an essential tool for diagnosing plant stress [13,[23][24][25]. ...
Getting around the damage caused by drought is a worldwide challenge, particularly in Brazil, given that economy is based on agricultural activities, including popcorn growing. The purpose of this study was to evaluate popcorn inbred lines under water stressed (WS) and well-watered (WW) conditions regarding agronomic attributes, root morphology, and leaf "greenness" index (SPAD index), besides investigating the viability of indirect selection by canonical correlations (CC) of grain yield (GY) and popping expansion (PE). Seven agronomic, six morphological root traits were evaluated and SPAD index at five different dates during grain filling. The WS (−29% less water than WW) affected significantly the GY (−55%), PE (−28%), increased the brace and crown root density, and more vertically oriented the brace and crown angles. Higher SPAD index is associated with a higher yield, and these measures were the only ones with no significant genotype × water condition interaction, which may render concomitant selection for WS and WW easier. For associating the corrections of the different traits, CC proved to have better potential than simple correlations. Thus, the evaluation of SPAD index at 29 days after the anthesis showed the best CC, and based on the previous results of SPAD index, may be used regardless of the water condition.
... Soil water depletion reduced the SPAD index regardless of genotypic groups. Foliar senescence induction is a plant response to water deficit conditions (Ghannoum, 2008;Araus et al., 2018), being coordinated by the reproductive stage of plants, but also strongly influenced by the environment (Combe and Escobar-Gutieŕrez, 2009). A portable chlorophyll meter (SPAD) can be an interesting tool for plant stress diagnosis (Romano et al., 2011;Araus et al., 2012;Zia et al., 2013;De Castro et al., 2014). ...
Climate change is expected to intensify water restriction to crops, impacting on the yield potential of crops such as popcorn. This work aimed to evaluate the performance of 10 field cultivated popcorn inbred lines during two growing seasons, under well-watered (WW) and water stressed (WS) (ψsoil≥ −1.5 MPa) conditions. Water stress was applied by withholding irrigation in the phenological phase of male pre-anthesis. Additionally, two contrasting inbred lines, P7 (superior line) and L75 (low performer) were compared for grain yield (GY) and expanded popcorn volume (EPV), selected from previous studies, were tested under greenhouse conditions. In the field, no genotype x water condition x crop season (G×WC×CS) interaction was observed, whereas GY (−51%), EPV (−55%) and leaf greenness (SPAD index) measured 17 days after anthesis (DAA) (> −10%) were highly affected by water limitation. In general, root traits (angles, number, and density) presented G×WC×CS interaction, which did not support their use as selection parameters. In relation to leaf senescence, for both WS and WW conditions, the superior inbred lines maintained a stay-green condition (higher SPAD index) until physiological maturity, but maximum SPAD index values were observed later in WW (48.7 by 14 DAA) than in WS (43.9 by 7 DAA). Under both water conditions, negative associations were observed between SPAD index values 15 and 8 days before anthesis DBA), and GY and EPV (r ≥ −0.69), as well as between SPAD index 7, 17, and 22 DAA, and angles of brace root (AB), number of crown roots (NC) and crown root density (CD), in WS (r ≥ −0.69), and AB and CD, in WW (r ≥ −0.70). Lower NC and CD values may allow further root deepening in WS conditions. Under WS P7 maintained higher net photosynthesis values, stomatal conductance, and transpiration, than L75. Additionally, L75 exhibited a lower (i.e., more negative) carbon isotope composition value than P7 under WS, confirming a lower stomatal aperture in L75. In summary, besides leaf greenness, traits related to leaf photosynthetic status, and stomatal conductance were shown to be good indicators of the agronomic performance of popcorn under water constraint.
... En maíz, la senescencia de las hojas está coordinada con la senescencia de toda la planta, que a su vez está influida por factores endógenos y ambientales (Combe y Escobar- Gutierrez, 2009). He et al. (2002) revelaron que existen dos tipos de senescencia, una precoz y una tardía. ...
La senescencia retrasada o “Stay Green” (SG) es un carácter deseable para la producción de los cultivos y está asociado con la producción de biomasa, resistencia al encamado y rendimiento. Esta investigación profundizó en los mecanismos genéticos y fisiológicos relacionados con la senescencia en maíz. Para ello, se evaluó el SG funcional de una amplia muestra de líneas de maíz templado, se identificaron QTL relacionados al carácter en una población MAGIC y se realizó un análisis de los cambios en la expresión génica durante la senescencia de la hoja. El SG funcional fue favorable para el rendimiento de grano, pero a costa del incremento de su humedad. Además, se propusieron dos genes candidatos asociados al índice de clorofila y se identificaron 1083 y 588 genes up and down regulated, respectivamente, durante la senescencia en las siete líneas. Los genes down y up regulated estuvieron relacionados con la fotosíntesis y con procesos catabólicos, respectivamente.
... It is also well known that photosynthetic functioning of leaves after silking is a major determinant of grain yield in maize (Tollenaar and Daynard, 1978; Tollenaar, 1999). In monocarpic species such as maize, senescence of leaves is coordinated with the senescence of the whole plant and influenced by the reproductive function and the environment (Smart, 1994; Combe and Escobar-Gutiérrez, 2009). Maize leaf senescence has been the object of much research from cellular to crop levels. ...
... Daily mean temperature, precipitation and reference evapotranspiration (ET 0 ) during the three growing seasons are presented inFig. 1. Growing degree-day (GDD) was calculated as the sum of daily mean temperature −6 @BULLET C that was considered the base temperature (Combe and Escobar-Gutiérrez, 2009).Table 2 Summary soil field capacity, permanent wilting point and water-holding capacity (WHC) of the experimental paddock where 'Déa' maize crops were grown during the years 1994, 1995 and 1996 at INRA's Research Centre, Thiverval-Grignon, France (after Tardieu et al., 1990) ...
... In Trial I, chlorophyll estimates were based on leaf optical density measured with a MacBeth TR-924 densitometer (Kollmorgen Corp., Newburgh, NY, USA). Details on the measurement procedure and the validation of the approach were previously described (Combe and Escobar-Gutiérrez, 2009). Nevertheless, in the present paper, chlorophyll content estimates were based on the 600–660 nm waveband rather than on the 510–570 nm. ...
a b s t r a c t The objective of this work was to describe the dynamics of senescence of field-grown maize from silking to harvest, at both leaf and plant level. At the leaf level, the dynamics of symptoms of senescence were considered on each leaf taken individually and described according to zones from the tip to the base of the leaf lamina. At the whole plant level, foliar ranks were each considered as an entity to describe the time course of senescence. To this end, we use a database built-up from field trials conducted during three consecutive years (1994–1996) and thus undergoing variable meteorological and soil water conditions. Leaf chlorophyll content was estimated using two different methods based on the optical properties of the leaves. In Trial I, chlorophyll estimates were based on leaf optical density measured with a MacBeth TR-924 densitometer. In Trial II and Trial III, chlorophyll estimations were based on measurement using a hand-held Minolta SPAD-502 device. In Trial II and Trial III, chlorophyll fluorescence analyses under filed conditions were performed. These analyses focused on the photosystem II (PSII) maximum efficiency (Fv /Fm) parameter in the light-adapted state. Measurements were done with a Waltz PAM-2000 portable fluorometer. We report detailed descriptions of the spatio-temporal dynamics of these indicators of senescence. We found that, after silking, a strong relationship exists between available water and leaf chlorophyll content. Further, the maximum efficiency of PSII decreased faster in maize plants undergoing low available soil water than in irrigated plants. The rank of a leaf is determinant of the time for the beginning of the decline in both chlorophyll content and maximum efficiency of PSII. At plant and leaf level, the onset of senescence was marked by a decrease in chlorophyll content that was not concomitant with a dramatic decrease in the maximum efficiency of PSII. Our analyses suggest that a non-linear functional relationship could exist between these two parameters during monocarpic senescence. In the mean time, the results presented in this paper could be used to refine the senescence related modules in plant and crop models.
... In monocarpic species such as maize, senescence of leaves is coordinated with the senescence of the whole plant and influenced by the reproductive function and the environment (Smart, 1994;Combe and Escobar-Gutiérrez, 2009). Maize leaf senescence has been the object of much research from cellular to crop levels. ...
... Daily mean temperature, precipitation and reference evapotranspiration (ET 0 ) during the three growing seasons are presented in Fig. 1. Growing degree-day (GDD) was calculated as the sum of daily mean temperature −6 • C that was considered the base temperature (Combe and Escobar-Gutiérrez, 2009). ...
... In Trial I, chlorophyll estimates were based on leaf optical density measured with a MacBeth TR-924 densitometer (Kollmorgen Corp., Newburgh, NY, USA). Details on the measurement procedure and the validation of the approach were previously described (Combe and Escobar-Gutiérrez, 2009). Nevertheless, in the present paper, chlorophyll content estimates were based on the 600-660 nm waveband rather than on the 510-570 nm. ...
In monocarpic species such as corn, senescence of leaves is coordinated with that of the whole plant and influenced by the reproductive function. The objective of the present study was to describe the evolution of corn senescence along two axes: (1) the whole-plant axis, where all foliar stages were each considered as an entity, and (2) the foliar axis, where the dynamics of three macroscopic symptoms of senescence was considered on each leaf taken individually, according to zones from the apex to the base of the leaf lamina. From a corn field culture, leaves were sampled or whole plants were submitted to a follow-up, from flowering to harvest. Dynamics of water, dry matter, and chlorophyll contents were different along the leaf as well as between ranking of leaves. Moreover, plant chlorophyll content followed a more complex dynamics than that of water and dry matter. From a follow-up of discoloration along leaves of 15 stems from top to bottom, authors have established functional relationships describing the advance of the senescence front for each foliar rank from 7 to top (rank 15 or 16). This quantitative description can be used directly in crop models as well as structure-function plant models. This would allow estimation of leaf-senescence impact on light-radiation interception and, therefore, on photosynthesis and productivity. Results can also be used for interpretation of reflectance measurements on corn canopies by remote sensing.
Context: Landraces are a potential source of genetic diversity and provide useful genetic resources to cope with the current and future challenges in crop breeding. Aims: The main objectives were to identify superior landraces with good level of agro-physiological traits, and high mean yield and stability performance. Methods: We evaluated a worldwide diversity panel of 196 durum wheat accessions originated from Iran and 17 other different countries along with four check varieties using an alpha-lattice design with two replications under drought and irrigated conditions in two cropping seasons. Key results: The results showed that the variance due to genotype and environment for all measured traits; and GE interaction for grain yield were significant (P<0.01). The genotype-by-traits (GT) biplot analysis revealed that the relationships of trait with grain yield were affected by environment, but some consistent correlations among studied traits were observed. SPAD, earliness and 1000-kernel weight positively correlated with mean yield under drought condition, while NDVI, plant height, days to heading and maturity positively correlated with yield under irrigated condition. The results verified that clustering pattern of durum diversity panel did not follow the grouping of accessions according to their geographic origins. Using GGE biplot accessions with high yield and stability performance were identified. Conclusions: The results provide possibility to select a subset of best accessions based on traits studied for further evaluations under drought and irrigated conditions. Implications: The findings are useful for selective breeding for specific traits as well as for enhancing the genetic basis of durum wheat breeding program.
