Morphogenesis on age categories of tillers in marandu palisadegrass

Abstract

Knowledge regarding morphogenetic characteristics has contributed to the understanding of plant responses to variations in climatic conditions and management practices. However, the original framework has been developed for temperate grass species, and indicates no ontogenetic effect on the expression of morphogenetic traits. Similar information for tropical grass species is scarce, but not less important. This experiment aimed at evaluating the influence of tiller age on the morphogenetic characteristics of continuously stocked marandu palisadegrass swards maintained at 30 cm and fertilized with nitrogen (N). Treatments corresponded to three nitrogen application rates (150, 300 and 450 kg ha -¹ of N) plus the control (no fertilization) and were assigned to experimental units (1,200 m 2 paddocks) according to a complete randomized block design, with four replications. The following response variables were measured during autumn/winter (Jun. to Jul. 2007) and summer (Feb. to Mar. 2008): leaf appearance rate (LAR), leaf elongation rate (LER) and the age profile of the tiller population. In general, LAR and LER were higher on young (< 2 months old) relative to mature (2 to 4 months old) and old (> 4 months old) tillers during both autumn/winter and summer. During autumn/winter swards were mainly comprised of old tillers (> 4 months old), the opposite happening during summer, when they were mainly comprised of young tillers. Overall, there was no N effect within tiller age categories. Tiller age was an important factor interfering with the morphogenetic responses of marandu palisadegrass, indicating that there is an ontogenetic effect on plant morphogenesis that should be considered further in future studies of this nature.

Structural characteristics of tiller age categories of continuously stocked marandu palisade grass swards fertilized with nitrogen

“…Therefore, rates of leaf appearance and elongation influence leaf size in opposite ways as a means of maintaining the structural characteristics of tillers and sward structure relatively stable. Further, there is an ontogenetic effect on morphogenetic characteristics of tillers, with young tillers having higher rates of leaf appearance and elongation than old tillers (Paiva et al, 2011). The fact indicates that in addition to stem length, the balance between leaf appearance and elongation is also an important factor determining the final length of leaves (Duru & Ducrocq, 2000b).…”

Identification of tiller age categories based on morphogenetic responses of continuously stocked marandu palisade grass fertilised with nitrogen

“…Nitrogen interferes with patterns of tiller appearance and death, altering the age profile of tiller population (PAIVA et al, 2011). Experiments have shown that tiller age influences the turnover of leaves on individual tillers (e.g.…”

“…According to KITAJIMA et al (1997), as plants mature their photosynthetic efficiency decreases, with potential negative effects on rates of leaf appearance and elongation (CARVALHO et al, 2001). The fact indicates that tiller age may be one of the main factors that determine morphogenetic responses to tropical forage grasses and highlights a strong ontogenetic effect related to tiller demography and patterns of tiller dynamics in the sward (PAIVA et al, 2011 …”

“…fertilisation, irrigation etc.) that promote increases in herbage production, like nitrogen fertilization, are related to the turnover of tillers in tiller populations, creating gradients of age with distinct potentials of response to environmental factors and management strategies (PAIVA et al, 2011) characterized by reduced rates of leaf appearance as tillers age (Figure 1). KITAJIMA et al (1997) commented on the strong effect that plant age has over its photosynthetic capacity, structural characteristics and potential productivity, highlighting the importance of knowledge regarding tiller age, variation in tiller age profile of the tiller population according to management practices used and their influence on herbage production.…”

Dynamics of forage accumulation in Elephant grass subjected to rotational grazing intensities

“…However, using a severe (high) post-grazing height can also reduce intraspecific light competition by modifying the light environment in the canopy and promoting increased tissue and tiller renewal, thereby resulting in a younger population of tillers. Some studies have suggested that tiller age influences both morphogenetic and structural characteristics, thereby resulting in a progressive loss of vigor with advancing tiller age (Paiva et al, 2011).…”