The leaf venation of angiosperms is key to their terrestirial dominance. These higher land plants include maple, corn, and ISS model organism Arabidopsis thaliana. The venation-dependent photosynthetic capacity of angiosperm leaves is largely responsible for terrestrial production of glucose and atmospheric oxygen, and may be fundamentally important to long-term space colonization. Leaf studies in orbit, where human-tended experiments are limited, can be enhanced by quantifying complex venation patterning. VESsel GENeration Analysis (VESGEN), a beta-level NASA software that analyzes vertebrate and human vascular branching for biomedical applications, is therefore being modified to map the branching venation patterns of dicot angiosperm leaves. By physiological branching rules, VESGEN decomposes a continuously connected vascular tree into its structural (dendritic) branching and reticulate (networked) capillary components.
For an arabidopsis juvenile leaf flown on NASA Space Shuttle Mission (STS)-130, the venation patterning of larger structural vessel orders 1°-2° remained relatively constant compared to normal gravity (by vessel number density Nv, 1.24E-5/micron2, and 1.29E-5/micron2, respectively). However, as a measure of increased venation maturity, Nv of smaller reticulate orders ≥ 3° increased considerably from 7.7E-6/micron2 in ground control to 1.74E-5/micron2 in the STS-130 leaf. Vascular geometric complexity is another feature of plant development that is governed in part by changes in gene expression patterns responding to environmental influence. We therefore propose that the mapping of leaf venation patterns by VESGEN can provide additional insight into plant responses to the spaceflight environment.
