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Ellen T. Paparozzi, Joshua R. Widhalm, and M. Elizabeth Conley

Common swedish ivy plants when exposed to nitrogen (N) stress display typical nitrogen deficiency symptoms such as reddening of stems and petioles and yellowing of leaves. When N levels are restored, leaves of swedish ivy plants will re-green without leaf loss. An experiment was conducted to determine how proteins change when leaves were re-greened after N deficiency. Cuttings of Plectranthus australis were rooted under mist and allowed to yellow. Plants were then potted up and fertilized with one of two treatments: complete nutrients with N at 150 ppm or complete nutrients with 0.8 ppm N. The experimental design was a randomized complete-block design with six blocks. Each block had the two N treatments and six plants per treatment. After 3–4 weeks, all plants in the 150-ppm N treatment had re-greened and leaf samples for protein analysis were taken. Plants in four of the six blocks were then switched to the other treatment. After leaves had re-greened once again, leaf samples were taken and the experiment was terminated. Two-dimensional polyacrylamide gel electrophoresis was used to compare the treatments. No obvious differences in protein absence or presence were noted. However, Rubisco appeared to be differentially expressed between the two treatments. 2-D gel analysis with subsequent Western blots showed that for most of the leaf samples, the large subunit of Rubisco (56kD) was quantitatively about 1.3 times more concentrated in the N-deficient plants and possibly modified. The small subunit (12kD) was not reliably detectable. Additional protein results for repeated leaf re-greening and the role Rubsico may play in leaf re-greening will be discussed.

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Paul V. Nelson


A series of experiments was conducted with chrysanthemum cv. Giant Betsy Ross grown in acid-washed quartz sand. The nutrient solution was buffered at pH 7.8 to induce Cu deficiency while Fe, Mn and Zn were supplied in high quantities to avoid simultaneous deficiencies. Nutrient levels in the tissues were monitered by atomic absorption analyses.

The critical range of Cu was established at 6.7 to 7.4 ppm for the first fully expanded leaves of the plant. The deficiency first appeared on the terminal leaves as chlorosis most intensely developed at the leaf blade base. As the leaf became more chlorotic the margin, and particularly the lobes toward the leaf apex, retained a normal green color. Tissues over and adjacent to the vascular tissue did not become as chlorotic as the leaf lamella giving rise to the second symptom which was interveinal chlorosis. At that stage the green pigmentation associated with the vascular tissue occurred in a broader pattern than in Fe deficiency. In the third stage of deficiency veinal chlorosis appeared, followed by necrosis of leaves located immediately below the first fully expanded leaf. There was a concomitant regreening of foliage at the terminal end of the shoot which lasted for a short time. In the final stage the shoot apex died.

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Ellen T. Paparozzi, Jazbaat K. Chahal, Petre Dobrev, Elizabeth A. Claassen, Walter W. Stroup, and Radomira Vankova

., 2009 ; Kiba et al., 2011 ). As cytokinins, often referred to as the leaf regreening hormone, also exhibit positive effects on chlorophyll concentration in leaves we decided to compare the dynamics of the response to N deficiency and subsequent N

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Cathryn Chapman, Stephanie Rossi, Bo Yuan, and Bingru Huang

increase in leaf hydration status and cell membrane stability, as well as a decrease in leaf senescence, as observed by higher chlorophyll content and greater photochemical efficiency ( Li et al., 2016 , 2017 ). Increased endogenous proline content has

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Dean A. Kopsell, James T. Brosnan, Gregory R. Armel, and J. Scott McElroy

, pigments increased beyond untreated levels by the end of the study. We hypothesize that temporary cessation of phytoene desaturase activity resulted in accumulations of phytoene in treated plants. On regreening of leaf tissues, and resurgence of phytoene

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Mahalaxmi Veerasamy, Yali He, and Bingru Huang

Temperatures greater than the optimal growth temperature negatively affect plant growth and induce various physiological and metabolic changes, including premature leaf senescence. Leaf senescence is characterized by loss of chlorophyll and

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Qi Chai, Fang Jin, Emily Merewitz, and Bingru Huang

important role in leaf dehydration tolerance as the coupled changes may prevent plasma membrane separation from cell walls or plasmolysis, which is critical for the maintenance of cell turgor and cell growth ( Nilsen and Orcutt, 1996 ). Re-greening and

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Timothy K. Broschat

( Ogden et al., 1987 ). Nitrogen, like P, K, and Mg, is a mobile element within palms. That is, under conditions of deficiency, the palm is able to extract N from the oldest leaves in the canopy and translocate it to the growing new leaf (spear leaf) to

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Brandon R. Smith and Lailiang Cheng

; Gonzalez-Vallejo et al., 2000 ; Larbi et al., 2001 ). It has been proposed that bicarbonate uptake increases the pH of xylem sap and leaf apoplast and interferes with foliar Fe utilization ( Mengel et al., 1984a , 1984b ), but this is not well-agreed on

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Charalambos I. Siminis and Manolis N. Stavrakakis

(II) to enable its transportation in the mesophyll cells ( Hell and Stephan, 2003 ). Ferric reduction capacity of leaf cells has been until now estimated in a few plant species with the use of intact leaves ( Kosegarten et al., 1999 ), excised leaf pieces