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Abstract Background Being able to accurately assess the 3D architecture of plant canopies can allow us to better estimate plant productivity and improve our understanding of underlying plant processes. This is especially true if we can monitor these traits across plant development. Photogrammetry techniques, such as structure from motion, have been shown to provide accurate 3D reconstructions of monocot crop species such as wheat and rice, yet there has been little success reconstructing crop species with smaller leaves and more complex branching architectures, such as chickpea. Results In this work, we developed a low-cost 3D scanner and used an open-source data processing pipeline to assess the 3D structure of individual chickpea plants. The imaging system we developed consists of a user programmable turntable and three cameras that automatically captures 120 images of each plant and offloads these to a computer for processing. The capture process takes 5–10 min for each plant and the majority of the reconstruction process on a Windows PC is automated. Plant height and total plant surface area were validated against “ground truth” measurements, producing R2 > 0.99 and a mean absolute percentage error

Abstract Background Existing methods for directly measuring photosynthetic capacity (A max) have low throughput, which creates a key bottleneck for pre-breeding and ecological research. Currently available commercial leaf gas exchange systems are not designed to maximize throughput, on either a cost or time basis. Results We present a novel multiplexed semi-portable gas exchange system, OCTOflux, that can measure A max with approximately 4–7 times the throughput of commercial devices, despite a lower capital cost. The main time efficiency arises from having eight leaves simultaneously acclimate to saturating CO2 and high light levels; the long acclimation periods for each leaf (13.8 min on average in this study) thus overlap to a large degree, rather than occurring sequentially. The cost efficiency arises partly from custom-building the system and thus avoiding commercial costs like distribution, marketing and profit, and partly from optimizing the system’s design for A max throughput rather than flexibility for other types of measurements. Conclusion Throughput for A max measurements can be increased greatly, on both a cost and time basis, by multiplexing gas streams from several leaf chambers connected to a single gas analyzer. This can help overcome the bottleneck in breeding and ecological research posed by limited phenotyping throughput for A max.

Ceptometry (the measurement of average photosynthetically active radiation under a plant canopy using many individual light sensors connected in parallel on a long bar) is commonly used to infer canopy light interception as well as leaf area index. Typically, the user places a ceptometer below the canopy and records a measurement, which is compared with a concurrent above-canopy measurement to produce a value of transmittance and then corrected for the effects of solar zenith and solar beam fraction. In row crops, canopy architecture is often systematically clumped in ways that may bias inferences based on ceptometer measurements. The role of spatial sampling in bias due to clumping has been extensively studied in the literature, but time-dependent bias has not. We assessed this bias using 68 handmade continuously recording ceptometers in 239 wheat ( L.) genotypes in Australia and made confirmatory measurements in California. We found that canopy properties inferred from instantaneous ceptometry varied widely, both randomly and systematically in time, when compared with properties inferred from continuous measurements. However, these biases tended to be somewhat similar across genotypes on a given day, arising from the interaction of solar zenith and non-random features of the canopy distribution caused by row planting. We recommend that continuous ceptometry be used in conjunction with instantaneous ceptometry to correct for these biases, and we provide schematics for low-cost handmade ceptometers.

Replacement of phospholipids with phosphorus (P)-free lipids in cellular membranes has been identified as a mechanism facilitating fast rates of photosynthesis when phosphorus availability is limited. We measured photosynthetic rates, leaf and soil P fractions, and foliar membrane lipid compositions for five species (Geranium antrorsum, Ranunculus graniticola, Poa costiniana, Poa hiemata, and Veronica derwentiana) common to two Australian subalpine ecosystems of contrasting parent material to characterize the extent to which they have adapted to long-term P availability. Our results indicate limited tolerance to reduced P, albeit adaptation strategies differ among species. Under reduced P conditions, phospholipids were replaced in foliage by galactolipids and sulfolipids, but photosynthesis was still impaired owing to reduced stomatal conductance. Accumulation of antioxidants, including carotenoids and alpha-tocopherol, in leaves with limited P supply suggests oxidative stress. Our field study shows that while subalpine Australian plants of a variety of life forms adapt to P availability by replacing phospholipids with P-free lipids in foliar membranes, this adaptation is insufficient to fully mitigate the effects of reduced P on photosynthesis.