SCIENTIFIC ARTICLE Morphological structure and physiology of sideoats grama genotypes [Bouteloua curtipendula (Michx.) Torr.] in their establishment stage Estructura morfológica y fisiología de genotipos de pasto banderilla [Bouteloua curtipendula (Michx.) Torr.] en su etapa de establecimiento abstract The objective of this study was to characterize the morphological and physiological attributes of eight genotypes of sideoats grama. Seven native Mexican genotypes of Bouteloua curtipendula (Michx.) Torr. (Poaceae) were collected in various parts of México and compared with a commercial variety (El Reno), which was used as a control. Plants were collected at six different stages: 50, 65, 80, 95, 110, and 125 days after sowing (das). We evaluated their morphological composition, aerial part:root ratio, growth rate (GR), specific leaf area (SLA), and net assimilation rate (NAR). Data were analyzed as a completely randomized block design with five replications; means were compared with the Tukey test (P<0.05). Regarding morphological composition, significant differences were observed in all genotypes for all stages (P<0.01). Genotypes 62 and 181 collected at 125 das showed a higher stem proportion when compared to the other morphological components. Genotypes 303, 125, and 5 showed the lowest proportions in root (P<0.05). The aerial part:root ratio was higher in genotype 303 (P<0.05). The root growth rate values obtained were similar among the proposed genotypes (P>0.05); however, all proposed genotypes presented higher values than El Reno (P<0.05). Likewise, the aerial part growth ratio values obtained showed that proposed genotypes presented higher values than El Reno (P<0.05). The results presented in this study show that genotypes 303, 125, and 5 had superior forage characteristics when compared to the commercial variety El Reno. These make such genotypes suitable species to be used in livestock activity. keywords Forage species, specific leaf area, growth rate, days after sowing. resumen El objetivo de este estudio fue caracterizar los atributos morfológicos y fisiológicos de ocho genoti-pos de pasto banderilla. Siete genotipos mexicanos de Bouteloua curtipendula (Michx.) Torr. (Poaceae), fueron recolectados de diversas partes de México y fueron comparados con una variedad comercial

✓ Describe the morphology and anatomy of different types of algae life forms. (20 marks) Question 2: ✓ Explain how the morphology and anatomy of algae are related to their size and habitats. (20 marks) Question 3: ✓ Describe the life cycle of algae (with the aid of diagrams). (30 marks)

Germination, growth and mineral distribution in Panicum turgidum Forsk. were investigated using 10-30% amended seawater (ECiw: 4.5-14.0 dS.m-1 ) for irrigation . Fifty percent reduction in germination (in Petri-plates) corresponded with ECiw: 6.72 dS.m-1 and threshold ECiw corresponding with 50% reduction in growth (in drum pot culture) was around 13.46 ± 0.51 dS.m-1.The plant showed good regeneration after bi-monthly clipping around the year except that growth was extremely reduced during winter season. The cumulative forage biomass harvested per annum with 30 % amended seawater (ECiw: 1 4.0 dS.m-1) was 1279.79 ±16.59 g.drum-1 (FW). It was 2851.85 ± 57.83 g.drum-1 (FW) in control (1.2 dS.m-1); reduction being c. 55%. The reduction in forage production in 10 and 20% seawater was c.23 and c.34% of the control, respectively. The plant showed flowering throughout the year. The plant irrigated with saline water showed decrease in chlorophyll and sugar contents and increase in proline level whereas moisture and protein concentration remained quite unaffected. The uptake of cations was selective. Sodium increased in the roots and shoots with almost equal magnitude and potassium declined in concentration with the salinity. There was, however, rapid translocation of potassium from roots to the shoots. The divalent cations like calcium and magnesium accumulated in greater concentration in the shoot.

1. The asymmetric competition for light and nutrients between floating and submerged aquatic plants is thought to be key in explaining why dominance by either of these groups can be stable and difficult to change.2. Although the shading effect of floating plants on submerged plants has been well documented, the impact of submerged plants on floating plants has been poorly explored hitherto.3. Here, we used laboratory experiments to examine how submerged plant (Elodea nuttallii) alter nutrient conditions in the water column and how this affects the growth of floating plants (Lemna gibba).4. We demonstrate that, at higher nutrient concentrations, Lemna is increasingly likely to outcompete Elodea.5. Under low nutrient concentrations (0.1–2 mg N L−1) Elodea can strongly reduce the growth of Lemna. Growth of floating plants virtually stopped in some of the experiments with Elodea.6. Extremely reduced tissue N, Mn, chlorophyll and elongated roots indicated that the growth inhibition of Lemna by Elodea was predominantly caused by the latter’s impact on the nutrient conditions for floating plants.7. These results strengthen the hypothesis that submerged plants can prevent colonization of a lake by floating plants.

The objective of this research is to evaluate the effect of salinity stress on morphology and anatomy of two leguminous range plants; Leucaena leucocephala and Prosopis chilensis plants. The investigated plants were irrigated with tap water (control) and two levels of salinity (3500 and 7500 ppm). Increasing salinity of irrigation water from 3500 to 7500 ppm led to reduction in plant height and stimulated the production of tannins in stems and leaflets of both investigated plants. This study demonstrated the presence of some anatomical changes induced by salinity in Leucaena leucocephala, and Prosopis chilensis leaflets. These anatomical changes included; presence of thick layer of cuticle, reduction in number of cortex layers and intercellular spaces between palisade cells, increase in the elongation of palisade parenchyma tissue and accumulation of tannin-filled cells in it , in cortical region of stem and also in parenchyma cells of its pith. All these anatomical modifications seemed to be crucial for their survival under salinity stress.