P. M. Room

Virtual plants: New perspectives for ecologists, pathologists and agricultural scientists

A new phase is under way in the study of how plants interact with their physical and biotic environments. Tools are becoming available for handling three-dimensional (3-D) information on the development and growth of individual plants and activities of the organisms which live on them. These tools will lead to in-depth understanding at the level of plant architecture, intermediate between what goes on at the level of plant cells and physiology and the level of plant stands and biomass. Existing fields of study will be enhanced and new fields opened. Here, we explain why these developments are important and how they are taking place

Computer-based cotton pest management in Australia

Abstract A prototype pest management system for cotton incorporating data handling and decision making by computer was progressively modified during 1978 and 1979 to increase its efficacy and practical feasibility. A more realistic assessment of crop status was developed. Threshold population densities of pests were revised. Labour requirements were reduced by sequentially sampling insects on terminals three times a week and by simulation of fruit development during week-long intervals between plant sampling. Decision making was refined using recent experience. The developing system, tested in 1978–1979 on a 14 ha field and in 1979–1980 on 360 ha of cotton grown on four farms, maintained yields at commercial levels although insecticide usage was decreased by 40%.

Architecture and morphogenesis of grain sorghum, Sorghum bicolor (L.) Moench

Plant architecture has been neglected in most studies of biomass allocation in crops. To help redress this situation for grain sorghum (Sorghum bicolor (L.) Moench), we used a 3D digitiser to measure the dimensions and orientations of vegetative and reproductive structures and derived thermal time-based functions for architectural changes during morphogenesis. Our plants, which were grown in a greenhouse, controlled environment cabinets and the field, covered a large, three-fold, size range when mature. This allowed us to detect some general architectural relationships and to fit morphogenetic functions common across the size range we observed. For example, the relationship between the lengths of successive fully-expanded leaves within a plant was nearly constant for all plants. The lengths of existing leaf blades were accurate predictors of the lengths of up to six subsequently-formed blades in our plants. Similar constant relationships were detected for internode lengths in the panicle and for heights above ground of the collars of successive leaves, even though these traits varied a lot between growth conditions. We suggest that such architectural relationships may be used to link the effect of previous growth conditions to future growth potential, and in that way to predict future partitioning. Our results provide the basis for a preliminary model of sorghum morphogenesis which could eventually become useful in conjunction with crop models by allowing resource acquisition to be related to changes in plant architecture during development

Virtual sorghum: visualisation of partitioning and morphogenesis

This paper presents a spatial simulation model of above-ground morphogenesis in a gramineous crop, grain sorghum (Sorghum bicolor (L.) Moench). Functions and parameters describing structural development were obtained from three-dimensional (3D) measurements of plants made at intervals during their development. The functions were expressed as specifications of morphogenesis in the L-system formalism and the specifications were interpreted by specialised software to create 3D virtual sorghum plants. Using the length and height of the collar of an early leaf as initial states, realistic images were generated of the lengths and shapes of subsequent leaves. The approach captures the dynamic interaction between partitioning and morphogenesis and presents the complex results as images that aid rapid interpretation.

Derivation of L-system Models from Measurements of Biological Branching Structures Using Genetic Algorithms

L-systems are widely used in the modelling of branching structures and the growth process of biological objects such as plants, nerves and airways in lungs. The derivation of such L-system models involves a lot of hard mental work and time-consuming manual procedures. A method based on genetic algorithms for automating the derivation of L-systems is presented here. The method involves representation of branching structure, translation of L-systems to axial tree architectures, comparison of branching structure and the application of genetic algorithms. Branching structures are represented as axial trees and positional information is considered as an important attribute along with length and angle in the database configuration of branches. An algorithm is proposed for automatic L-system translation that compares randomly generated branching structures with the target structure. Edit distance, which is proposed as a measure of dissimilarity between rooted trees, is extended for the comparison of structures represented in axial trees and positional information is involved in the local cost function. Conventional genetic algorithms and repair mechanics are employed in the search for L-system models having the best fit to observational data.

Interaction between Helicoverpa armigera and Colletotrichum gloeosporioides on the tropical pasture legume Stylosanthes scabra

Glasshouse experiments determined effects of a moth, Helicoverpa armigera (Lepidoptera: Noctuidae), and the anthracnose pathogen, Colletotrichum gloeosporioides (Penz.) Penz. and Sacc., on each other when attacking the same host plant, Stylosanthes scabra (Vog.) (Leguminosae) cv. Fitzroy. The host was treated with both organisms in 2 ways of succession and at 2 different life stages each. Larvae of the moth preferred to feed on healthy plants rather than plants recently infected with C. gloeosporioides, and preferred such newly infected plants to severely diseased ones. Adult female moths laid more eggs on healthy and recently infected plants than on diseased plants, when given a choice of all 3 plant types. Severity of anthracnose disease was neither promoted nor retarded by damage to leaves caused by larvae of the moth.