Why Would a Fruit Tree Crop Physiologist Kill to Easily Measure the following?
Tree water status is fundamental for growth and productivity. Gas exchanges at leaf level depend on water availability, and they are important because: i) they allow CO2 to enter the leaf, so photosynthesis can occur; ii) the leaf controls its temperature by evaporating H2O in the substomatal cavity, absorbing latent heat of evaporation in the process; iii) as water reaches the leaves, a stream of nutrients, hormones, carbohydrates, and other substances needed for growth is transported from the roots to the canopy. The sheer volume of this stream is impressive: a fruit tree of modest size (e.g. not taller than 4 m) can transpire up to 20 liters of water per day. While we have a strong array of tools to gauge this movement within the plant, to date we lack non-destructive, low-cost, digital solutions to monitor water movement within the tree. Some tools exist to gauge the tension the leaves must generate to draw water from the roots, but they could be improved. Precise irrigation inputs could be determined by knowing the amount of work a tree is performing to extract water from the soil and lift it to the canopy. Currently, a plant-based sensor is commercially available, which provides a continuous monitoring of stem water potentials, but it has drawbacks consisting of high price and limited use (normally 1 growing season). Other plant based sensors include dendrometers, to gauge trunk shrinkage/expansion, disease sensors, electronic insect traps, soil sensors for macronutrients availability, fruit diameter gauges, in addition to weather stations that can be deployed in the orchard to provide real-time temperature, relative humidity, wind and rain data. Weather data is very useful if it can be combined with plant performance indicators. Fruit growth is possibly the most interesting indicator of a tree’s well-being, as it is the result of many processes that growers try to control, in order to maximize orchard productivity. Growth is the result of water and carbohydrate inflows to the fruit, via the xylem and the phloem vascular systems, and the water outflow through the fruit epidermis. All three flows are affected by local environmental conditions, in addition to genetic and physiological determinants. Fruits differ for the type of mechanism that is supporting their growth, but knowledge is available regarding which type is adopted by a specific fruit, like apple, at any time during its growing season. This session will be designed to present some physiological determinants of tree behavior, and then discuss potential solutions for novel sensors. The goal is provide thought-provoking insights for interested minds.
Luca Corelli Grappadelli is Professor of Fruit Growing at the University of Bologna (Italy). He has an extensive research career, spanning almost 40 years, in the field of fruit tree ecophysiology. He has been quite active at the international level, with a total of 3.5 years in the US (Clemson and Cornell Universities) and Australia (Tatura Center for Excellence). His work has covered tree/leaf gas exchanges, carbon partitioning, water relations and fruit growth. This has led to current research in precision fruit growing, including novel training systems, agrivoltaics, autonomous electric vehicles, precision irrigation in IoT, fruit growth forecasting. He is/has been involved in a number of international research projects, within, but also outside Europe. He is Chair, ISHS Division “Temperate Tree Fruits” (2022-2026). He is also Chair of the “Environmental Physiology and Developmental Biology” Working Group of ISHS (since 2016), and has convened/co-convened 3 ISHS Symposia, and edited the respective proceedings. He is Editor of the industry monthly magazine, Rivista di Frutticoltura (Edagricole Bologna). During his tenure at Unibo he has taught classes in Fruit Tree Physiology, Arboriculture, Viticulture. He has supervised/co-supervised 18 PhD students, and a number of MSci students as well.