A. San Bautista

Effects of grafting and cytokinin-induced fruit setting on colour and sugar-content traits in glasshouse-grown triploid watermelon.

Summary The effect on fruit quality of grafting and fruit set treatments, was determined in the triploid watermelon (Citrullus lanatus (Thun.) Matsum. and Nakai) cultivar ‘Reina de Corazones’ grown in a heated greenhouse. Grafting the scion onto ‘Shintoza’ (Cucurbita maxima × Cucurbita moschata) rootstock and setting fruit through application of the synthetic cytokinin CPPU [1-(2-chloro-4-pyridyl)-3-phenylurea] retarded the accumulation of sugar and development of the flesh colour of the fruit, compared to fruit from non-grafted, pollinated plants. The effects of grafting and of CPPU application on sugar accumulation were additive. At commercial maturity, the fruit of grafted and/or CPPU-treated plants had lower total soluble solids and sugar concentrations, and lower sucrose to hexose ratios, than fruit from control plants. Fruit from CPPU-treated plants also had a weaker red colour than fruit set by pollination. Despite this loss of quality, fruit from grafted plants, set with CPPU and grown in a heated greenhouse, had a total soluble solids concentration similar to fruit from pollinated, non-grafted plants, grown outdoors.

Growth and nutrient absorption in chufa (Cyperus esculentus L. var. sativus Boeck.) in soilless culture

Summary The efficiency of fertilisation in agriculture is often low and, provided one knows the nutrient uptake rate, the efficiency can be improved by synchronising nutrient supply with nutrient demand. Growth, the time-course of nutrient accumulation and its partitioning between different organs in chufa (Cyperus esculentus L. var. sativus Boeck.), an under-exploited cultivated plant, were examined. The study was conducted in soilless, open-field conditions, at a planting density equivalent to 55,500 plants ha−1 in three consecutive seasons. Plants were sampled, fractionated into leaves, roots, and tubers, then dried and weighed. Their macronutrient contents were analysed each fortnight. On average, the yield was 5.0 kg fresh weight of tuber m−2. Growth of whole plants, until 90 d after planting, obeyed an exponential function of time. The relative growth rate (RGR) for this period was therefore determined. The highest N and K concentrations were recorded in leaves, and the highest P, Ca, and Mg concentrations were found in roots. The highest accumulations of N and P were found in tubers, and of K and Ca in leaves. Nitrogen had the highest nutrient accumulation (58.3 g m−2) as well as the highest specific uptake rate.

Influence of cation proportions of the nutrient solution on tipburn incidence in strawberry plants.

ABSTRACT To determine their influence on leaf tipburn incidence and yields six nutrient solutions with different proportions of potassium (K), calcium (Ca), and magnesium (Mg) were tested in ‘Camarosa’ strawberry plants. Response models were made to predict tipburn incidence, yields and fruit weight. A high Ca proportion in the nutrient solution was determinant for high yields in the first season, while a high Mg content was fundamental for high marketable yields during the two last seasons. In 2001 and 2002, the average fruit weight was higher with high Mg levels, and in 2000 the lowest fruit weights coincided with low levels of Ca in the nutrient solution. The models for tipburn incidence in 2000 and 2002 indicated that solutions with intermediate to high levels of Mg and intermediate to low levels of Ca resulted in a more frequent incidence of tipburn. Conversely, in 2001, the highest tipburn incidence appeared with high K contents.

Enhancing root systems of waiting-bed strawberry plants grown on substrates

Summary To find techniques to improve root system development of waiting-bed strawberry plants ‘Camarosa’ grown in substrates, the influence of two substrates (peat and coconut coir dust), or plants from three waiting-beds at different altitudes, and of root treatments with different plant growth regulators (naphthalenacetic acid at 25, 50 and 75 mg g–1; indolebutyric acid at 10, 20 and 30 mg g–1; l-triacontanol at 0.02, 0.04 and 0.06 mg g–1) by dipping runners prior to planting, were studied in two experiments in the 1997–98 and 1998–99 seasons. In both years, plants from high elevation beds (HE) produced the greatest root development, and plants from medium elevation beds (ME) produced more new roots than those from low elevation beds (LE). Root development of plants grown in peat was greater than those grown in coconut coir dust in the first experiment and only on the first measuring dates (one month after planting). This difference was particularly high in plants from high or medium elevation nurseries, when the degree of root development was greater. No differences between substrates were observed in the second experiment. Treatments with the different growth regulators tested, at any of the concentrations used, did not improve root development on average for the other factors.

Effect of different levels of nitrogen in nutrient solution and crop system on nitrate accumulation in endive

ABSTRACT With the objective of studying the effect of two nutrient solutions and two crop systems (greenhouse and openfield) on nitrate accumulation, incidence of tipburn and chlorophyll content, endive (cv. Cuartana) was planted in 8 L pots, filled with a mixture of coconut coir:perlite (1:1) in three different cycles C1 (winter), C2 (spring) and C3 (summer). Plants were irrigated with two nutrient solutions of different nitrate content: S1, low ([NO−3] = 7.91 mmol L−1) and S2 moderate nitrate content ([NO−3] = 16.91 mmol L−1). Nitrate content was determined by reflectometry, tipburn was evaluated using a qualitative scale and chlorophyll content by soil plant analysis development(SPAD) values. Plants irrigated with S2 showed higher nitrate accumulation in leaves in all cycles, however, no influence of the nutrient solution was observed on the incidence of tipburn. Greenhouse-cultivated plants accumulated more nitrates than those cultivated in open field and also showed a higher incidence of tipburn and SPAD values.

Chlorophyll fluorescence imaging can reflect development of vascular connection in grafting union in some Solanaceae species

Graft union development in plants has been studied mainly by destructive methods such as histological studies. The aim of this work was to evaluate whether the chlorophyll fluorescence imaging (CFI) technique is sensitive enough to reflect changes at the cellular level in different Solanaceae grafted plants 30 d after grafting, when both grafted partners were well fused and strong enough in all plant combinations. The pepper cultivar ‘Adige’ was grafted onto different Capsicum spp. accessions typified with different compatibility degrees; eggplant was grafted on Solanum torvum and pepper homografts as compatible unions; pepper was grafted on S. torvum and on tomato as incompatible unions. ‘Adige’/’Adige’ and ‘Adige’/pepper A25 showed a higher maximum quantum efficiency of PSII associated with higher values of actual quantum efficiency of PSII and photochemical quenching as well as with vascular regeneration across the graft interface. Our results highlighted that CFI changes reflected histological observations in grafted Solanaceae plants.

Growth and nutrient absorption of Cape Gooseberry (Physalis Peruviana L.) in soilless culture

Cape gooseberry (Physalis peruviana L.) is a solanaceous plant. The growth and time-course of nutrient accumulation of the plant and its partitioning between roots, stems, leaves, and fruits were examined. The study was conducted analyzing two nutrient solutions in soilless culture under greenhouse conditions during two consecutive seasons. The macronutrient contents were analyzed. On average, the yield was 8.9 t·ha−1. Growth of the plant until 90 d after transplanting obeys an exponential function of time and the relative growth rate for this period was determined. Nitrogen (N) was the element that showed the highest concentration, corresponding to leaves (4.67%), followed by potassium (K) in stems (4.46%). The highest accumulations of N, phosphorous (P), calcium (Ca), and magnesium (Mg) were found in leaves and of K in the stems. Potassium showed the highest nutrient accumulation (29 g·plant−1) and the highest specific uptake rate.