Absorption and Distribution of Copper in Plants with Sufficient or Deficient Supplies

Wheat, red clover and ryegrass were grown in flowing solutionculture with sufficient (+ Cu) and deficient (–Cu) suppliesof copper. The rates of Cu absorption (µg g^–1 dryroot day^–1) did not differ greatly between species ineither treatment. Wheat plants, when transferred from the –Cu to the +Cu treatment, absorbed Cu at a much slower rate thanthose which had remained throughout in the + Cu treatment. Inall plants considerable proportions of the absorbed Cu wereretained in the roots, even when the plants were Cu-deficient,and the concentration in roots usually exceeded that in anypart of the shoots in both treatments. Transferring wheat plantsfrom the +Cu to the –Cu treatment decreased the concentrationin all plant parts except old leaves; similarly, transferringfrom the –Cu to +Cu treatment increased the concentrationin all parts of the shoots, execept old leaves, and in the roots. Lolium perenne, Trifolium pratense, Triticum aestivum, ryegrass, red clover, wheat, absorption, copper, flowing solution culture     

The Growth and Development of Simulated Swards of Perennial Ryegrass: II. Carbon Assimilation and Respiration in a Seedling Sward

The rates of net photosynthesis (P_n,c) in the light (85 W m^–2visible), and respiration in the dark, of a simulated swardof S24 ryegrass were measured for 12 weeks during its developmentfrom a collection of two-leaved seedlings to a closed canopywith an LAI of 23 (15 of green leaf laminae). By the sixth week light interception was complete (LAI = 10.6)and P_n,c had risen to 24 mg CO₂ dm^–2 h^–1, similarto rates recorded in the field. Photosynthetic functions (lightresponse curves) showed that the swards remained unsaturatedup to energy receipts of almost 400 W m^–2, whereas singleleaves were light saturated at about 130 W m^–2. Earlyin the development of the sward LAI had a greater effect onP_n,c than radiation receipt, later the reverse was true. Thegrowth habit of the sward ranged from moderately erect (an Svalue of 0.72) to moderately prostrate (‘S’ = 0.37),while the ability of the two youngest fully expanded leaveson a tiller to make use of light in photosynthesis declinedas the sward increased in density from values of A max of 20to 5 mg CO₂ dm^–2 h^–1. By varying the values of Sand A max fed into a model of canopy photosynthesis, withinthe above limits, it was demonstrated that, in practice, A maxis a greater determinant of canopy photosynthesis than S, exceptat low LAI where a prostrate sward has a marked advantage overan erect one. The rate of dark respiration rose as the swards increased inweight, although not in proportion to it, until the ninth weekwhen a ceiling yield of live plant tissue was reached. Respiratorylosses from the sward came almost equally from a component associatedwith maintenance (R_m) and one associated with growth (R_g). Therate of Rm was estimated to be about 0.014 g day^–1 pergram of plant tissue, and that of Ra about 0.25 g per gram ofnew tissue produced—both close to theoretical values.The measured dry matter production curve of the swards was comparedwith that estimated from the gas analysis data. Similarly therates of gross photosynthesis estimated from the gas analysisdata were compared with the predictions of the mathematicalmodel. In both cases the fit was reasonably good. A balancesheet was drawn up; of every 100 units of carbon fixed, 45 werelost in respiration and 16 as dead leaf, 5 ended up in the rootand 6 in the stubble; only 28 remained as harvestable live leaftissue.     

Effect of Phosphorus Deficiency and Water Deficit on Phosphatase Activities from Wheat Leaves

Wheat was sown in a phosphorus (P) deficient soil. Plants atlow levels of applied P had lower growth rates and lower concentrationsof phosphate in the shoots than plants grown with ‘highP’. Activities of both insoluble and soluble phosphataseincreased with P deficiency in the mature leaves. Soluble phosphataseactivities increased 2.5–3.0 fold as the concentrationof phosphate in the leaves fell from 0.4% to 0.1% dry weightThis increase was not a consequence of reduced growth, as severenitrogen deficiency had no effect on phosphatase activity. Soluble phosphatase activities were higher in young than inmature leaves, and also increased 3–4 fold with severewater deficit. However these increases in activity were notaccompanied by low concentrations of phosphate. Moreover, solublephosphatase activities in mature leaves of plants grown underconditions of water deficit rapidly decreased after rewatering.In contrast, the high soluble phosphatase activities in matureleaves of P deficient wheat persisted for up to 12 d after theresupply of P to adequate levels.     

The Effects of Copper Supply and Shading on Retranslocation of Copper from Mature Wheat Leaves

Plants of Gamenya wheat (Triticum aestivum L.) were grown inpots of a Cu-deficient sand at two levels of Cu (deficient andsufficient), and harvested on days 13, 22, 28 and 38. In 50per cent of the pots in each Cu treatment, the oldest leaf andleaf 2 of the main stem were shaded when they reached full expansion. The Cu content of the oldest leaf of Cu-sufficient, unshadedplants was high at day 13 and declined rapidly to day 38. Thatof Cu-deficient, unshaded plants was initially relatively lowand declined much more slowly, so that at day 38 it resembledthat of Cu-sufficient plants. Shading the oldest leaf acceleratedthe loss of its Cu in both Cu-deficient and Cu-sufficient plants.The effects of shading and of Cu supply on the loss of Cu fromthe oldest leaf paralleled their effects on the loss of N andchlorophyll. The results suggest that most of the Cu in theoldest leaf does not move out until the leaf senesces. In Cu-deficient plants retention of Cu by old green leaves accentuatedCu deficiency. The release of Cu, resulting from shading theold leaves of Cu-deficient plants, stimulated the growth ofnew leaves. In Cu-sufficient plants, shading depressed growth. copper, shading, retranslocation, wheat, Triticum aestivum L.     

The Effect of Copper Supply on the Senescence and the Retranslocation of Nutrients of the Oldest Leaf of Wheat

The contents of Cu, N, P, K, Zn, Mn and Ca were followed duringthe life of the oldest leaf of wheat plants (Triticum aestivumL. cv. Gamenya) grown at deficient and sufficient supplies ofCu. At both levels of Cu, the Cu content of the oldest leafbehaved in a similar way to the contents of N and Zn, whichdeclined markedly during leaf senescence. By contrast to Cu the P and K contents declined markedly, priorto leaf senescence, whereas the Ca and Mn contents increasedthroughout the life of the leaf and did not decline during leafsenescence. Interactions among Cu supply, the supply of other nutrients(e.g. N), and leaf senescence account for the variable mobilityof Cu in wheat. Similar interactions between nutrient supplyand senescence may explain contradictory reports on the redistributionof other nutrients which are variably mobile in plants.