SOIL FERTILITY AFFECTS ELEMENTAL DISTRIBUTION IN NEEDLES OF THE CONIFER Araucaria angustifolia: A MICROANALYTICAL STUDY

Abstract

Araucaria angustifolia is a conifer species found in South American subtropical forests that comprises less than 3% of the native vegetation and little is known concerning the accumulation of nutritional elements in its needles. In this study, scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) was used to assess the elemental distribution in needles. Needles were selected from 28 month-old plants grown in a fertilization experiment supplied with: 1) N, P, and K; 2) N and P; and 3) N and K. In microanalysis, four types of specialized needle tissues (adaxial epidermis, palisade mesophyll, spongy mesophyll and abaxial epidermis) were evaluated for elemental composition (C, O, P, K, Ca, S and Al). When crystals were detected, the concentrations of 12 elements were determined (C, O, P, K, Ca, S, Al, Fe, Mg, Na, Si, and Cl). Under low soil P and K, these elements were found in low concentrations in the epidermis, mesophyll, and crystals. Under low soil P, Ca and K accumulated in the spongy mesophyll, while under low soil K only Ca accumulated in this tissue. In addition, low soil P or K availability favored the formation of crystals; crystals under low soil K availability had more Ca and Mg. Soil P and K availability affected the distribution of elements in needles of A. angustifolia, in that type of tissue and formation of crystals were key to the nutrient dynamics in needles.

INITIAL GROWTH OF Araucaria angustifolia ROOTSTOCK IN RESPONSE TO FERTILIZATION WITH NITROGEN, PHOSPHORUS AND POTASSIUM

“…Whereas we found no differences in K treatments, Simões and Couto (1973) reported that seedlings of A. angustifolia with K deficiency showed lower height, altered branch angles, and smaller old leaves with yellowing at the extremities. For seedlings of A. angustifolia that received no K and had low levels in needles, Barbosa et al (2017) reported an abnormal increase of Ca oxalate crystal formation in needles and Ca in the mesophyll. Although added K did not alter the growth of A. angustifolia seedlings ( Figure 5), it is worth noting that our study was conducted under ideal moisture conditions, which does not often occur in the field.…”

Elemental composition and nutritional value of Araucaria angustifolia seeds from subtropical Brazil

“…Seed Ca and Mg variations may be due to reduced Ca phloem transport aggravated by lower transpiration of fruits compared to leaves. In addition, Ca has less remobilization from leaf and branch tissues since it is predominantly associated with cell walls (White 2012) and oxalate crystals (Barbosa et al 2017).…”

Linking geographical origin with nutritional, mineral, and visual proprieties of pinhão (Araucaria angustifolia seed) from the south of Brazil

“…This may be attributed to different plant metabolisms among the different plants, variations in soil nutrients such as nitrogen, or a combination of these factors. A previous study (Barbosa et al., 2017) indicated that the availability of P and K in the soil affected the accumulation of these elements in the epidermis, whereas the type of tissue and crystal formation were key characteristics for the dynamics of the nutrients in the epidermis of A. angustifolia .…”