Differential capacity of nitrogen assimilation between apical and basal leaf portions of a tank epiphytic bromeliad

Abstract

The leaf is the main organ of the vegetative body of tank epiphytic bromeliads, which may be subdivided into apical and basal parts. Little is known about the existence of morphological, anatomical or physiological differences between these two leaf portions. The objective of this study was to verify the existence of a differential capacity to assimilate nitrogen from urea between basal and apical leaf portions of Vriesea gigantea, a tank epiphytic bromeliad. Plants were cultivated in vitro in the presence of 5 mM urea for 15 days. During this period, the activities of the enzymes glutamine synthetase (GS, EC 6.3.1.2) and NADH-dependent glutamate dehydrogenase (NADH-GDH, EC 1.4.1.2) were quantified, as well as the densities of trichomes and stomata found at the leaf surface of both regions. The highest activities of GS and NADH-GDH were always detected at the top portion, and on the 3rd day of in vitro cultivation an increase in these activities was detected. An inverse correlation between number of trichomes and stomata in these two leaf portions was verified: the top region presented 30% less trichomes and twice as many stomata as the basal region. This suggests that the upper region of the leaf may be preferentially involved with the assimilation of nitrogen from urea via GS and NADH-GDH, whereas the basal region may be involved with its absorption. This is the first study to report that ammonium assimilation may take place preferentially in a specific portion of tank-forming bromeliad leaves.

Specific leaf areas of the tank bromeliad Guzmania monostachia perform distinct functions in response to water shortage

“…Therefore, besides anatomical modifications, functional differences are also expected to occur along the leaf blade of these bromeliads (Benzing, 2000;Takahashi et al, 2007). In agreement, the data obtained here demonstrated that different leaf regions of G. monostachia can perform distinct roles during the physiological responses triggered by changes in one of the most significant variables in the epiphytic niche, the water availability (Zotz and Hietz, 2001).…”

<b> Physiological characteristics of the Atlantic Forest native bromeliads: <i>Nidularium campo-alegrense</i> Leme and<i> Aechmea ornata</i> Baker </b> - doi: 10.4025/actascibiolsci.v36i1.20215

“…In the apical portion of the leaves of the bromeliad Vriesea gigantea it was found the highest concentrations of starch. This suggests that this region has the highest photosynthesis rates in relation to the base, and consequently the higher availability of energy, reducing power and carbon skeletons (TAKAHASHI et al, 2007). The greatest accumulation of sugars in the portion of the leaf apex was also observed in Ananas comosus cv.…”

Assimilação do nitrogênio em folhas de Vriesea gigantea (Bromeliaceae) durante a transição ontogenética do hábito atmosférico para o epífito com tanque

“…Sakai & Sandford (1980), ao estudarem os tricomas presentes nas superfícies foliares de Ananas comosus (Bromeliaceae), observaram que os tricomas presentes no ápice apresentavam-se não funcionais, diferentemente dos tricomas da base. Nessa mesma bromélia terrestre, Popp et al (2003) & Mercier, 2003;Nievola et al, 2001;Tamaki & Mercier, 2001;Inselsbacher et al, 2007;Takahashi et al, 2007).…”