Retranslocation of nutrients in coffee leaves of cultivars Red Catuaí IAC 144 and IAC 125 RN

Knowledge of the retranslocation of nutrients in plants can help in the management of coffee fertilization, especially with regard to the ideal time and method of application and the need for installments. The aim of this study was to evaluate the retranslocation of nutrients in coffee leaves of two varieties. The treatments consisted of two varieties of coffee (Red Catuaí IAC 144 and IAC 125 RN) and coffee leaves in four phenological stages (young leaves, diagnostic, senescent and deciduous). The index leaf of Catuaí Vermelho IAC 144 showed the highest photosynthetic rate and stomatal conductance, while the internal conductance of CO2 was higher in young and senescent leaves, and the index and senescent leaves showed the highest efficiencies in the use of water. The chlorophyll a, b and total chlorophyll has higher concentrations in the index leaf, while the highest carotenoids occurred in young and senescent leaves. The highest levels of N, P, K and Zn in Catuaí Vermelho IAC 144 was occurred in young leaves and the highest Ca and Fe in senescent leaves. The highest levels of N, P and K in the IAC 125 RN variety was occurred in young leaves, Ca and Mg in deciduous leaves and S in senescent and deciduous leaves. Nutrients with low mobility in the plant must be parceled, the application of Zn leaves is an alternative method of supplying this nutrient, as it has retranslocation via phloem

Influences of light and humidity on carbonyl sulfide-based estimates of photosynthesis

Understanding climate controls on gross primary productivity (GPP) is crucial for accurate projections of the future land carbon cycle. Major uncertainties exist due to the challenge in separating GPP and respiration from observations of the carbon dioxide (CO2) flux. Carbonyl sulfide (COS) has a dominant vegetative sink, and plant COS uptake is used to infer GPP through the leaf relative uptake (LRU) ratio of COS to CO2 fluxes. However, little is known about variations of LRU under changing environmental conditions and in different phenological stages. We present COS and CO2 fluxes and LRU of Scots pine branches measured in a boreal forest in Finland during the spring recovery and summer. We find that the diurnal dynamics of COS uptake is mainly controlled by stomatal conductance, but the leaf internal conductance could significantly limit the COS uptake during the daytime and early in the season. LRU varies with light due to the differential light responses of COS and CO2 uptake, and with vapor pressure deficit (VPD) in the peak growing season, indicating a humidity-induced stomatal control. Our COS-based GPP estimates show that it is essential to incorporate the variability of LRU with environmental variables for accurate estimation of GPP on ecosystem, regional, and global scales.

To concentrate or ventilate? Carbon acquisition, isotope discrimination and physiological ecology of early land plant life forms

A comparative study has been made of the photosynthetic physiological ecology and carbon isotope discrimination characteristics for modern-day bryophytes and closely related algal groups. Firstly, the extent of bryophyte distribution and diversification as compared with more advanced land plant groups is considered. Secondly, measurements of instantaneous carbon isotope discrimination ( Δ ), photosynthetic CO 2 assimilation and electron transport rates were compared during the drying cycles. The extent of surface diffusion limitation (when wetted), internal conductance and water use efficiency (WUE) at optimal tissue water content (TWC) were derived for liverworts and a hornwort from contrasting habitats and with differing degrees of thallus ventilation (as intra-thalline cavities and internal airspaces). We also explore how the operation of a biophysical carbon-concentrating mechanism (CCM) tempers isotope discrimination characteristics in two other hornworts, as well as the green algae Coleochaete orbicularis and Chlamydomonas reinhardtii . The magnitude of Δ was compared for each life form over a drying curve and used to derive the surface liquid-phase conductance (when wetted) and internal conductance (at optimal TWC). The magnitude of external and internal conductances, and WUE, was higher for ventilated, compared with non-ventilated, liverworts and hornworts, but the values were similar within each group, suggesting that both factors have been optimized for each life form. For the hornworts, leakiness of the CCM was highest for Megaceros vincentianus and C. orbicularis (approx. 30%) and, at 5%, lowest in C. reinhardtii grown under ambient CO 2 concentrations. Finally, evidence for the operation of a CCM in algae and hornworts is considered in terms of the probable role of the chloroplast pyrenoid, as the origins, structure and function of this enigmatic organelle are explored during the evolution of land plants.