Portable chlorophyll meter (PCM-502) values are related to total chlorophyll concentration and photosynthetic capacity in papaya (Carica papaya L.) Fernanda Assumpc ¸a ˜o De Castro • Eliemar Campostrini • Alena Torres Netto • Mara De Menezes De Assis Gomes • Tiago Massi Ferraz • David Michael Glenn Received: 19 February 2014 / Accepted: 17 August 2014 / Published online: 24 August 2014 Ó Brazilian Society of Plant Physiology 2014 Abstract This study was carried out to verify the practical use of the portable chlorophyll meter- PCM502 (PCM) in two papaya cultivars with con- trasting 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 % 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, F v /F m (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 F v /F m 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 signifi- cantly 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 \ 30 ‘Sunrise Solo’ had a greater rate of F v /F m 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 physiolog- ical alterations related to N metabolism. Keywords Chlorophyll content Á Photosynthesis Á Photochemical efficiency 1 Introduction Papaya (Carica papaya L.) is an important horticultural crop of tropical and subtropical regions. Knowledge of F. A. De Castro Á E. Campostrini (&) Á M. De Menezes De Assis Gomes Á T. M. Ferraz Plant Physiology Laboratory, Agricultural Science and Technology Center, Northern Rio de Janeiro State University, Campos Dos Goytacazes, Rio de Janeiro, Brazil e-mail: campostenator@gmail.com A. T. Netto LBCT, Northern Rio de Janeiro State University, Campos Dos Goytacazes, Rio de Janeiro, Brazil D. M. Glenn USDA-ARS, Appalachian Fruit Research Station, Kearneysville, WV, USA 123 Theor. Exp. Plant Physiol. (2014) 26:201–210 DOI 10.1007/s40626-014-0018-y