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Accueil du site → Doctorat → États-Unis → 1995 → Physiological and developmental responses of normal and dense pubescent soybeans (Glycine max (L.) Merr.) to water stress

University of Nebraska - Lincoln (1995)

Physiological and developmental responses of normal and dense pubescent soybeans (Glycine max (L.) Merr.) to water stress

Gandoul Ibrahim Gandoul

Titre : Physiological and developmental responses of normal and dense pubescent soybeans (Glycine max (L.) Merr.) to water stress

Auteur : Gandoul Ibrahim Gandoul

Université de soutenance : University of Nebraska - Lincoln

Grade : Doctor of Philosophy (PhD) 1995

Résumé
Water and temperature stresses are the most limiting factors for crop production in many dry land production systems. The need to understand and relate responses of essential physiological processes to yield limiting plant developmental processes is important. Experiments were conducted to evaluate soybean responses to water stress in terms of net carbon exchange (NCE), transpiration (TR), respiration (R), assimilate partitioning and growth. Dense (CD) and normal (CN) pubescent Clark soybean isolines were grown under wet and dry conditions. Biomass, leaf area (LA) and leaf area index (LAI), plant height, canopy NCE, canopy and pod R were measured during selected growth stages. Differential responses to water stress in total dry matter production were greatest under dry conditions where the CN isoline produced 10% less total dry matter than the CD. The CD isoline partitioned 20% of its dry matter to reproductive organs compared to 12% for CN. Early in the season when temperatures were high, the CD had 20% higher LAI than the CN. Midday values of NCE were higher for CD isoline than for CN. Similarly, TR and canopy temperature were lower in the CD than in CN. Net carbon exchange was depressed at low soil moisture when vapor pressure deficit (VPD) was more than 3.0 kPa and air temperature (T$\sb\rm a$) was 35.5$\sp\circ$C. Low soil moisture, high T$\sb\rm c$ and VPD resulted in 3$\sp\circ$C higher canopy temperature (T$\sb\rm c$) in CN than CD. High T$\sb\rm c$ probably caused stomatal closure which resulted in decreased NCE.^ Respiration rates were higher under wet conditions than dry conditions presumably due to higher carbon assimilation. Under dry conditions the CN isoline had higher respiration rates than the CD isoline. This may be due to higher maintenance respiration requirements in the CN because of greater water stress. There were no significant differences between the two isolines for pod respiration rates. The proportion of pod respiration to total canopy respiration ranged from 18 to 37% depending on the growth stages and soil moisture content.^ Leaf growth and expansion were significantly different between isolines. Dense isolines had higher leaf expansion rates than the normal isolines. Results indicate that the dense pubescent isolines performed better under water and temperature stresses than the normal isolines. Incorporating dense pubescence in other legumes adapted to dry land areas particularly in the semi-arid tropics seems useful. ^

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Page publiée le 17 septembre 2010, mise à jour le 28 décembre 2018