scholarly journals Recovery from Phytotoxicity after Foliar Application of Fruit-loosening Abscission Compounds to Citrus

2008 ◽  
Vol 133 (4) ◽  
pp. 535-541 ◽  
Author(s):  
Kuo-Tan Li ◽  
Jacqueline K. Burns ◽  
James P. Syvertsen
Keyword(s):  
Foliar Application ◽  
Sweet Orange ◽  
Fruit Growth ◽  
Mature Fruit ◽  
Photosystem Ii Efficiency ◽  
Young Fruit ◽  
Leaf Chlorophyll ◽  
Phytotoxic Effect ◽  
High Concentrations ◽  
Leaf Chlorophyll Fluorescence

The use of abscission compounds to loosen fruit from stems can be accompanied with various levels of phytotoxicity. To determine the effects of a promising abscission compound, 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP), and ethephon on sweet orange [Citrus sinensis (L.) Osbeck] leaf function, water relations, and young fruit growth, we sprayed CMNP at 0, 200, 500, 1000, or 2000 mg·L−1 or ethephon at 400 or 800 mg·L−1 to fruiting branches of potted and field-grown sweet orange during the 2005–06 harvest season. Both compounds induced abscission of mature fruit and leaves 3 days after application but had little effect on leaf chlorophyll content, water content, and midday leaf water potential (Ψleaf) of remaining leaves. CMNP sprayed at 200 mg·L−1 or either concentration of ethephon did not affect leaf photosystem II efficiency, as indicated by leaf chlorophyll fluorescence (Fv/Fm). High CMNP concentrations (1000 or 2000 mg·L−1) reduced Fv/Fm 1 day after treatment, but Fv/Fm of leaves remaining on sprayed branches gradually recovered to the level of control leaves by 4 days after treatment. Similarly, high concentrations of CMNP and ethephon temporarily reduced net gas exchange of leaves for about 4 days. Young fruit growth also was temporarily inhibited by CMNP concentrations greater than 200 mg·L−1. We conclude that CMNP sprayed at recommended concentrations (200–500 mg·L−1) caused mature fruit abscission with little long-term phytotoxic effect on leaves or young fruit.

scholarly journals Association between Fruit Development and Mature Fruit Drop in Huanglongbing-affected Sweet Orange

HortScience ◽  
2020 ◽  
Vol 55 (6) ◽  
pp. 851-857
Author(s):  
Lisa Tang ◽  
Sukhdeep Singh ◽  
Tripti Vashisth
Keyword(s):  
Fruit Development ◽  
Sweet Orange ◽  
Water Status ◽  
Fruit Size ◽  
Substantial Reduction ◽  
Fruit Growth ◽  
Mature Fruit ◽  
Callose Deposition ◽  
Immature Fruit ◽  
Fruit Drop

In the past decade, FL citrus industry has been struck by Huanglongbing (HLB), a disease caused by the phloem-limited bacterium Candidatus Liberibacter asiaticus (CLas). Besides tree decline, HLB causes a sharp increase in mature fruit drop before harvest, leading to a substantial reduction in citrus production. The aim of the study was to provide insights in HLB-associated mature fruit drop. For HLB-affected ‘Valencia’ and ‘Hamlin’ sweet orange (Citrus sinensis), trees exhibiting severe symptoms (“severe trees”) had a significantly higher rate of mature fruit drop compared with mildly symptomatic ones (“mild trees”). Interestingly, dropped fruit were smaller than those still attached to tree branches regardless of the symptom levels of trees; overall, fruit of severe trees were smaller than mild trees. The result suggests a negative effect of HLB on fruit growth that may lead to a high incidence to drop subsequently at maturity. This possibility is further supported by the difference in immature fruit size as early as 2 months after bloom between severe and mild trees. Although HLB-triggered phloem plugging due to callose deposition in citrus leaves, which results in disrupted carbohydrate transport, has been documented in literature, the results of the histological analysis demonstrated no consistent pattern of callose deposition in the mature fruit pedicel in relation to the drop incidence. Additionally, sugar concentration in juice was not significantly different between dropped and attached fruit, providing evidence that carbohydrate shortage is not the case for dropped fruit and thus not the predominant cause of HLB-associated mature fruit drop. Notably, the midday water potential was significantly lower for severe than mild trees during the preharvest period (2 weeks before harvest of the current crop) in late March, which was also the second week after full bloom of return flowering. This suggests that altered tree water status due to HLB might limit fruit growth during the initial stage of fruit development (immediately after flowering) and/or increase the incidence of mature fruit abscission, leading to elevated preharvest fruit drop. Together, the results suggest that in the presence of HLB, strategies to increase fruit size and minimize additional stresses (especially drought) for the trees may improve mature fruit retention.

scholarly journals Pilot Cultivation of the Local Endemic Cretan Marjoram Origanum microphyllum (Benth.) Vogel (Lamiaceae): Effect of Fertilizers on Growth and Herbal Quality Features

Agronomy ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 94
Author(s):  
Dimitrios Fanourakis ◽  
Konstantinos Paschalidis ◽  
Georgios Tsaniklidis ◽  
Vasileios A. Tzanakakis ◽  
Fotis Bilias ◽  
...  
Keyword(s):  
Nutrient Management ◽  
Foliar Application ◽  
Nutrient Content ◽  
Natural Ecosystems ◽  
Endemic Plant ◽  
Nutrient Contents ◽  
Leaf Chlorophyll ◽  
Antioxidant Compound ◽  
Local Endemic ◽  
Leaf Chlorophyll Fluorescence

Wild phytogenetic resources are threatened by overexploitation. This pressure on species and natural ecosystems can be alleviated in part by recruiting and domesticating wild-growing species under pilot cultivation with tailor-made fertilization schemes. This study focused on the pilot cultivation of Origanum microphyllum—a critically endangered local endemic plant of Crete, Greece—investigating the effect of conventional and integrated nutrient management (ΙΝΜ) fertilizers by foliar or root application and biostimulant. Above-ground biomass together with leaf chlorophyll fluorescence and color (SPAD meter, DA meter, Chroma Meter) were determined. Leaf chlorophyll, antioxidant compound (carotenoids, phenols, flavonoids), and nutrient contents were also assessed. The results showed that fertilization did not significantly affect plant growth and leaf nutrient content. Root fertilization was associated with greener leaves compared to foliar. The same trend was generally evident for antioxidant compound content. The small size of leaves may have impeded the efficiency of the foliar application. In conclusion, root application of conventional or INM fertilizers seems more suitable to promote visual quality and herbal antioxidant profile of O. microphyllum, than the foliar one.

A COMPARATIVE ANALYSIS OF LEAF CHLOROPHYLL FLUORESCENCE, HILL REACTION ACTIVITY AND 14C-ATRAZINE TRACER STUDIES TO EXPLAIN DIFFERENTIAL ATRAZINE SUSCEPTIBILITY IN WILD TURNIP RAPE (Brassica campestris) BIOTYPES

1984 ◽  
Vol 64 (3) ◽  
pp. 707-713 ◽  
Author(s):  
A. ALI ◽  
V. SOUZA MACHADO
Keyword(s):  
Chlorophyll Fluorescence ◽  
Brassica Campestris ◽  
Foliar Application ◽  
Decisive Role ◽  
Hill Reaction ◽  
Turnip Rape ◽  
Leaf Chlorophyll ◽  
Leaf Chlorophyll Fluorescence ◽  
The Hill ◽  
Hill Reaction Activity

Leaf chlorophyll fluorescence in susceptible B. campestris L. plants was greatly enhanced and the Hill reaction activity of isolated chloroplasts was inhibited by 10−4 M atrazine. The herbicide did not produce similar responses in resistant plants. 14C-atrazine was used to determine if, in addition, there were differences in uptake, translocation, and metabolism of the herbicide by the susceptible and resistant biotypes. The 14C-atrazine in nutrient solution was readily taken up by the roots of both biotypes and was rapidly translocated to the shoot. The 14C-atrazine was quickly metabolized and after a 24-h period 56 and 63% of the extractable radioactivity in susceptible and resistant plants, respectively, was present as metabolites, the major one being 2-hydroxyatrazine. Following a foliar application, less than 1% of the applied radioactivity moved into other parts of the plant. These results clearly show that triazine resistance in wild turnip rape is based in the chloroplast and that uptake, translocation, and metabolism of the herbicide play no decisive role in selectivity between the susceptible and resistant biotypes.Key words: Atrazine selectivity, Brassica campestris, chlorophyll fluorescence, Hill reaction, atrazine metabolism.

scholarly journals Effects of 5-chloro-3-methyl-4-nitro-1H-pyrazole and Ethephon on Citrus Leaf Function and Water Relations

HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 1008A-1008
Author(s):  
Kuo-Tan Li ◽  
Jackie Burns ◽  
Luis Pozo ◽  
Jim Syvertsen
Keyword(s):  
Photosystem Ii ◽  
Water Relations ◽  
Leaf Water ◽  
Leaf Water Content ◽  
Fruit Peel ◽  
Photosystem Ii Efficiency ◽  
Citrus Leaf ◽  
Content Ratio ◽  
High Concentrations ◽  
Leaf Chlorophyll Fluorescence

To determine the effects of abscission compounds 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) and ethephon on citrus leaf function and water relations, we applied CMNP at 0, 200, 500, 1000, or 2000 ppm, or ethephon at 400 or 800 ppm, to canopies of fruiting potted and field citrus trees during the harvest season. Both compounds induced fruit and leaf drop after 3 days of application, especially at high concentrations. Low concentrations of CMNP (0, 200, or 500 ppm) or either ethephon treatments did not affect leaf photosystem II efficiency, as indicated by leaf chlorophyll fluorescence (Fv/Fm). High concentrations of CMNP (1000 or 2000 ppm) immediately reduced photosystem II efficiency in leaves and fruit peel. However, Fv/Fm of leaves remaining on the trees was gradually restored and close to the level of control after 4 days of treatment. Both compounds had little effect on chlorophyll content, ratio of chlorophyll a to chlorophyll b, leaf water content, and mid-day leaf water potential. The results suggest that CMNP at recommended concentrations (200 to 500 ppm) effectively reduced fruit attachment force with little herbicidal effect on leaves.

scholarly journals (90) Young Tree Growth and Leaf Function of Citrus Seedlings under Colored Shade Netting

HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 1022C-1022 ◽  
Author(s):  
Kuo-Tan Li ◽  
Jim Syvertsen
Keyword(s):  
Dry Weight ◽  
Young Tree ◽  
Photosystem Ii Efficiency ◽  
Chlorophyll Contents ◽  
Leaf Chlorophyll ◽  
Shade Cloth ◽  
Total Plant ◽  
Leaf Chlorophyll Fluorescence ◽  
Cleopatra Mandarin ◽  
Poncirus Trifoliate

Young citrus trees and seedlings in Florida's commercial nurseries are often grown under shade cloth netting to avoid high light and temperature. To investigate the potential benefit of altering radiation by colored shade nets, `Cleopatra' mandarin (Cleo, C. reticulata Blanco) seedlings and potted `Valencia' trees [Citrus sinensis (L.) Osbeck] on Cleo or Carrizo [Carr, C. sinensis × Poncirus trifoliate (L.) Raf.] rootstocks were grown in full sun or under 50% shade from blue, black, silver, grey, and red colored shade nets. Changes in photosynthetically active radiation (PAR) and temperatures under the shade were monitored. Leaf function and leaf chlorophyll contents were measured, and plants were harvested by the end of the experiment for shoot and root growth measurements. Plants under the shade received an average of 45% PAR and had lower mid-day leaf temperature than plants in full sun. Plants under blue nets had greatest leaf chlorophyll a, b, and total chlorophyll content, whereas those under red nets had the lowest. However, shading improved photosystem II efficiency from measurements of leaf chlorophyll fluorescence (Fv/Fm) regardless of the color of shade nets. Shading increased shoot growth, shoot to root ratio, and total plant dry weight of Cleo seedlings, especially those under silver nets.

Leaf chlorophyll fluorescence discriminates herbicide resistance inEchinochloaspecies

Weed Research ◽  
2016 ◽  
Vol 56 (6) ◽  
pp. 424-433 ◽  
Author(s):  
C J Zhang ◽  
S H Lim ◽  
J W Kim ◽  
G Nah ◽  
A Fischer ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Herbicide Resistance ◽  
Leaf Chlorophyll ◽  
Leaf Chlorophyll Fluorescence

The limits of sodium/calcium interactions in plant growth

2000 ◽  
Vol 27 (7) ◽  
pp. 709 ◽  
Author(s):  
Robert J. Reid ◽  
F. Andrew Smith
Keyword(s):  
High Salinity ◽  
Foliar Application ◽  
Maximum Growth ◽  
Growth Responses ◽  
Wheat Seedlings ◽  
Low Salinity ◽  
High Concentrations ◽  
Main Component ◽  
Dependent Processes ◽  
Root Plasma Membrane

The amelioration of Na toxicity by supplementation of Ca in the growth medium was investigated in wheat with the aims of (1) identifying the Ca-dependent processes that determine the growth responses and (2) defining the limits to Ca effects on these processes. Growth of wheat seedlings was strongly inhibited by 150 mM NaCl but improved as the Ca concentration in the nutrient medium was increased up to 2.34 mM. Further increasing Ca to 10 mM did not increase growth, nor did foliar application of Ca. Even at high concentrations of Ca, the maximum growth was only approximately 50% of the growth at low salinity. We conclude that the main component of improved growth caused by Ca was via its apoplastic effects on the transport of Na and K across the root plasma membrane, rather than by increasing root or shoot Ca concentrations. There was no evidence that high salinity inhibited Ca uptake to the shoot. The limits to improvement of growth by Ca appear to relate to the fact that, although Ca is able to ameliorate the toxicity caused by high intracellular Na, it is not able to overcome the osmotic deficits associated with high salinity.

Sign in / Sign up

Export Citation Format

Share Document