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Title: Portable chlorophyll meter (PCM-502) values are related to total chlorophyll concentration and photosynthetic capacity in papaya (Carica papaya L.)

Author
item CASTRO, FERNANDA - Universidade Estadual Do Norte Fluminense
item CAMPOSTRINI, ELIEMAR - Universidade Estadual Do Norte Fluminense
item NETTO, ALENA - Universidade Estadual Do Norte Fluminense
item GOMES, MARA - Universidade Estadual Do Norte Fluminense
item FERRAZ, TIAGO - Universidade Estadual Do Norte Fluminense
item Glenn, David

Submitted to: Theoretical and Experimental Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2014
Publication Date: 8/24/2014
Citation: Castro, F., Campostrini, E., Netto, A., Gomes, M., Ferraz, T., Glenn, D.M. 2014. Portable chlorophyll meter (PCM-502) values are related to total chlorophyll concentration and photosynthetic capacity in papaya (Carica papaya L.). Theoretical and Experimental Plant Physiology. DOI 10.1007/s40626-014-0018-y.

Interpretive Summary: Measuring plant status is complicated due to the many factors that affect plant growth, such as fertility, water availability, disease and insect damage and air pollution. The biochemical action of chlorophyll responds to many of these environmental factors since it drives photosynthesis and growth. We examined the usefulness of two simple-to-operate and inexpensive devices that measure chlorophyll activity: 1) portable chlorophyll meter-PCM502 (PCM) and 2) Portable Chlorophyll Meter (SPAD meter). PCM and SPAD meters were able to diagnose deficiencies related to nitrogen availability in papaya. The use of these instruments will aid growers in managing nitrogen fertilization, and reducing nitrogen runoff and groundwater pollution.

Technical Abstract: This study was carried out to verify the practical use of the portable chlorophyll meter-PCM502 (PCM) in two papaya cultivars with contrasting green coloring of the leaf blade (‘Golden’: yellowish-green; ‘Solo’: dark green). The relationship was studied between the photosynthetic process and leaf nitrogen concentration, chlorophyll concentration and SPAD readings. The Portable Chlorophyll Meter (or SPAD meter) is a simple, portable, accurate, fast and inexpensive tool. Two Carica papaya L cultivars were grown in a greenhouse with 30 percent interception in the photosynthetic active radiation (PAR). At 90 and 100 days after sowing (DAS), two groups of leaves from each cultivar were used for experiments. One group was considered as “young” leaves (3rd or 4th leaf from the apex), and one group as “mature” leaves (6th or 7th leaf from the apex). In these experimental conditions, the following parameters were measured: net photosynthesis, Fv/Fm (potential maximal quantum yield of PSII), total chlorophyll concentration and leaf organic nitrogen. At SPAD values lower than 20 for ‘Golden” and 30 for ‘Solo’, the Fv/Fm ratios were correlated with the increase in the ratio as determined by the PCM. There were cultivar differences related to N allocation in the leaf. ‘Golden’ partitioned significantly less N to chlorophyll synthesis than ‘Solo’ at equivalent leaf N concentrations. This explains, in large part, the yellowish green leaf coloring of ‘Golden’ papaya. These cultivar differences in chlorophyll concentration were measurable with PCM technology. In contrast, at SPAD values less than 30, ‘Sunrise Solo’ had a greater rate of Fv/Fm decline than ‘Golden’ indicating that ‘Sunrise Solo’ was more sensitive to damage to PSII when N was limiting. At 90 and 100 days after planting and with adequate water availability, PCM technology was able to evaluate the total chlorophyll molecules and maximum efficiency of PSII, meaning that the equipment can be used to diagnose physiological alterations related to N metabolism.