Photosynthetic capability and Fe, Mn, Cu, and Zn contents in two Moraceae species under different phosphorus levels

Abstract

The strong adaptability of Broussonetia papyrifera (L.) Vent. to low phosphorus (P) conditions can be attributed to the large amount of root-exuded organic acids and the high efficiency of P extraction. However, microelement contents are influenced by low-P stress, and their effects on the photosynthetic capability of B. papyrifera remain unknown. In this study, we investigated the effects of low-P treatment on net photosynthetic rate (P N ); chlorophyll a fluorescence (ChlF) characteristics; and Fe, Mn, Cu, and Zn contents of B. papyrifera and Morus alba L. seedlings. Results show that B. papyrifera exhibited better photosynthetic capability under moderate P deficiency (0.125, 0.063, and 0.031 mmol/L P treatments), whereas the photosynthetic capability of M. alba decreased under moderate and severe P deficiency (0.016 and 0 mmol/L P treatments). Under moderate P deficiency, the decrease in Cu and Zn contents in B. papyrifera was lower than that in M. alba. Under severe P deficiency, a considerable decrease of photosynthetic capability in B. papyrifera and M. alba was associated with low Cu and Zn contents. The P N of the two Moraceae species exhibited a better correlation with Cu and Zn contents than with Fe or Mn content. P deficiency could not only decrease cyclic photophorylation and photosynthetic efficiency, but could also affect the stability of thylakoid membrane structure and electron transport efficiency by influencing the contents of Cu or Zn, thereby affecting photosynthesis.

Effects of Zn Deficiency and Bicarbonate on the Growth and Photosynthetic Characteristics of Four Plant Species

“…It also inhibited plant growth indirectly through increased pH, which led to a decrease in available nutrient elements, such as Zn, iron, and copper, and then inhibited plant growth via two pathways. In the first pathway, excess HCO 3 − initially appeared in all plants as chlorosis related to nutrient element deficiency [24], a considerable decrease of photosynthetic capability was associated with the lower Zn contents [25], followed by the inhibition of PS II activity and decreased photosynthetic parameters, such as P N and WUE, and Chl fluorescence parameters, such as Fo, Fv/Fm, and ETR. In the second pathway, excess HCO 3 − decreased the Zn concentration in plant tissue and the CA activity involved in photosynthetic carbon metabolism, in addition to inhibiting the HCO 3 − -use capacity because the substrates provided by HCO 3 − alleviated the CA-catalytic conversion reaction.…”