Nitrogen Use within the Growing Leaf Blade of Tall Fescue

Abstract

Leaf elongation rate (LER) of grasses depends on N supply and i s expressed mostly through cell production, whereas most N in mature leaf tissues is chloroplastic. Our objective was to evaluate a possible competition for N between cell production and chloroplast development processes, utilizing the gradient of cell development along the leaf growth zone of tal1 fescue (Festuca arundinacea Schreb.). Under the two contrasting N regimes, total N content was highest in the cell production zone, declined sharply as cells elongated, and remained relatively constant in more dista1 positions, at values close to those measured in mature tissues. A similar pattern was found for N in proteins and nucleic acids that were not soluble in 80% ethanol. Content of N compounds soluble in 80% ethanol was higher in the cell production and elongation zones than in mature parts of the leaf. NO,-N content was low in the cell production zone and increased in the cell elongation zone for high-N plants. l h e deposition rate of total N in the growth zone was much higher with plants in high N than in those shifted to no N. For both N regimes, most N was deposited during cell production and early cell elongation. Little N was deposited during cell maturation where ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was being actively synthesized. lhis suggests that synthesis of Rubisco, and probably other chloroplastic proteins, occurs largely from recycling of N that was previously incorporated into proteins during cell production. Thus, Rubisco content in mature tissues is more closely associated with N deposited during cell production than with N deposited during its biosynthesis.

Morphogenetic traits and biomass accumulation of Brachiaria brizantha cv. Xaraés subjected to nitrogen doses

“…Other studies evaluating effects of N on leaf elongation rate also presented similar results (Gastal & Nelson, 1994;Alexandrino et al, 2000). According to Volenec & Nelson (1994), the increase in leaf elongation rate, caused by nitrogen fertilization is due to a greater cell production, with little effect on the final size of the cell or on epidermal cell elongation rate.…”

“…Morphogenetic traits can be subdivided into: leaf appearance rate; leaf elongation rate and leaf senescence rate, in addition to stalk elongation for tropical grasses (Sbrissia & Da Silva, 2001). Leaf elongation rate of the grasses is very responsive to N fertilization (Gomide et al, 2006).…”

Sward structure of marandu palisadegrass subjected to continuous stocking and nitrogen-induced rhythms of growth

“…This was corroborated by the results of a concomitant experiment carried out in the same area involving measurements of morphogenetic responses to treatments imposed (Table 4). Gastal and Nelson (1994) commented that nitrogen can generate a three to four fold increase in leaf elongation rate (LER), suggesting that this is the main morphogenetic response to nitrogen fertiliser application. Although LER is the characteristic determining acceleration of the growth rhythm of plants, tiller population density (TPD) plays an important role in increasing herbage bulk density and herbage mass on nitrogen fertilised swards (Fagundes et al, 2006;Mesquita et al, 2010).…”

Grass strategies and grassland community responses to environmental drivers: a review

“…The leaf elongation rate and the length of the leaf growth zone (region where cell division and expansion occurs) exhibit negative correlations to leaf dry matter content (Arredondo and Schnyder 2003). Leaf nitrogen content is closely associated with N deposited during cell production (Gastal and Nelson 1994). Therefore, Pontes et al (2007) have suggested that N yield declines with N deposition per unit cell volume in the growth zone.…”