ABSTRACT
Vertical farming can produce food in a climate-resilient manner, potentially emitting zero pesticides and fertilizers, and with lower land and water use than conventional agriculture. Vertical farming systems (VFS) can meet daily consumer demands for nutritious fresh products, forming a part of resilient food systems-particularly in and around densely populated areas. VFS currently produce a limited range of crops including fruits, vegetables and herbs, but successful implementation of vertical farming as part of mainstream agriculture will require improvements in profitability, energy efficiency, public policy and consumer acceptance. Here we discuss VFS as multi-layer indoor crop cultivation systems, exploring state-of-the-art vertical farming and future challenges in the fields of plant growth, product quality, automation, robotics, system control and environmental sustainability and how research and development, socio-economic and policy-related institutions must work together to ensure successful upscaling of VFS to future food systems.
ABSTRACT
Phospholipase D (PLD, EC 3.1.4.4.) has been implicated in a variety of plant processes, including signalling. In Arabidopsis thaliana a PLD gene family has been described and individual members classified into alpha-, beta- and gamma-classes. Here we describe a second PLD gene family in tomato (Lycopersicon esculentum) that includes three alpha- and two beta-classes. Different expression patterns in plant organs were observed for each PLD. In testing a variety of stress treatments on tomato cell suspensions, PLDbeta1 mRNA was found to rapidly and specifically accumulate in response to the fungal elicitor xylanase. The greatest increase was found 2 h after treatment with 100 microg m1(-1) xylanase (ninefold). In vivo PLD activity increased nearly threefold over a 1.5 h period of treatment. When the elicitor was injected into tomato leaves, PLDbeta1 mRNA accumulation peaked at 2 h (threefold increase), before decreasing to background levels within 72 h. Mutant, non-active xylanase was as effective as the active enzyme in eliciting a response, suggesting that xylanase itself, and not the products resulting from its activity, functioned as an elicitor. When chitotetraose was used as elicitor, no PLDbeta1 mRNA accumulation was observed, thus it is not a general response to elicitation. Together these data show that PLD genes are differentially regulated, reflecting potential differences in cellular function. The possibility that PLDbeta1 is a signalling enzyme is discussed.