Light Acclimation in Citrus Leaves. II. CO2 Assimilation and Light, Water, and Nitrogen Use Efficiency

Abstract

Net CO2 assimilation (A) rates of ‘Duncan’ grapefruit (Citrus paradisi Macf.) and ‘Pineapple’ orange (C. sinensis L.) seedlings grown under 3 different photosynthetic photon flux densities (PPFD), were measured in an open gas exchange system under controlled environmental conditions. Apparent quantum yield (ø), mesophyll conductance to CO2 (Gm), leaf conductance to H2O vapor (G1), transpiration (E) and water use efficiency (WUE) also were examined. Leaves of both species grown under high PPFD (full sunlight) had the greatest maximum rates of A, but the low PPFD (90% shade) leaves had the highest ø. The WUE of low PPFD grapefruit leaves was less than that of the high PPFD leaves but increased within 2 weeks after being moved into full sunlight. Transferring seedlings from low to high PPFD decreased ø of grapefruit but not of orange leaves. Changes in A were more strongly correlated to Gm than to G1. Carbon dioxide assimilation rate was positively correlated to total leaf nitrogen content. Citrus leaf photosynthetic characteristics and resources use efficiency not only acclimate to the light regimes under which they expand and mature, but leaves are capable of acclimating to new light regimes, even after full maturation.

Influence of Anthocyanin Expression on the Performance of Photosynthesis in Sweet Orange, Citrus sinensis (L.) Osbeck

“…Nevertheless, VvmybA1 leaves acclimate through increased efficiency of transfer from Qa to Qb to achieve the same PItot as wild-type leaves. This suggests that these trees may perform better under high-irradiance and high-temperature conditions, conditions that typically reduce productivity as they require greater investment in photoprotective mechanisms [49,50]. Moreover, the efficiency/probability with which a PSII-trapped electron is transferred from QA to QB (as measured by ΨET20) was higher in VvmybA1 leaves, possibly compensating for the reduction in photon absorption.…”

Stress Symptoms of Citrus Trees in Successive Stages of Decline Due to Blight

“…Previous studies described normal rates of photosynthesis (17) in leaves of declining trees with blight, but the leaf N content was elevated. Nitrogen content usually can be positively correlated to rates of net gas exchange (18), but in the case of blight, these leaves of higher N content have only normal photosynthesis, which may mean that these leaves are not producing at their potential. The lower N levels of trunk bark and wood of trees in Block 2 compared to Block 1 may have been due to the different rootstocks, since Zn levels have been shown to differ with rootstocks (2).…”

“…Trunk bark (2) and wood (27) samples from opposite sides of the tree and leaf samples (10-leaf composite from southeast side) were collected during Summer 1983 and dried for elemental analysis. Trunk and leaf tissue samples were digested and N determined by Kjeldahl analysis (18). Similar samples were ashed at 550°C for 6 hr, dissolved in 25% aqueous HC1, and diluted to give 5% HC1 solutions of appropriate element concentrations for atomic absorption analysis for Zn, Mn, Cu, K, and Na (2,22,27).…”

Net CO2 Assimilation Rate and Nitrogen Content of Grape Leaves Subsequent to Fruit Harvest

“…Gutierrez et al (11) have recently developed a vine growth model which was structured to allow for the effect of leaf age on photosynthesis. The observed changes in leaf N content throughout the growing season (33,37) and the effect of position within the canopy (light regime) on leaf photosynthetic capacity, N and protein content (16,22,31,32), suggest that N content would be a better indicator of a leafs photosynthetic potential than chronological age. Thus, the linear relationship between grapevine leaf net C 0 2 assimilation rate and leaf N content, both expressed on a dry weight basis (Fig.…”