Factors influencing glassiness in lettuce.

Abstract

Glassiness, a physiological disorder occurring in greenhouses between November and February under low natural light conditions, is probably due to an imbalance between water uptake and transpiration. Eight greenhouse experiments were carried out during winter. Experiments with soil-grown plants showed that soil compaction and nitrogen supply were negatively correlated with the amount of glassiness whereas the amount of nightly outgoing radiation (from inside the greenhouse) was positively correlated with glassiness. Studies using the nutrient film technique showed that the positive effect of nitrogen was probably due to higher salt concentration rather than a specific effect of NO₃^-. Clear cultivar differences were observed with Dalida, Mistra and Rolinda showing less glassiness than Renate, Amanda Plus and Decisco. High soil compaction, high plant temperature, tolerant cultivars and higher total salt concentration could all be used to reduce glassiness. (Abstract retrieved from CAB Abstracts by CABI’s permission)