No abstract

No abstract

The life span of leaves increases with their mass per unit area (LMA). It is unclear why. Here, we show that this empirical generalization (the foundation of the worldwide leaf economics spectrum) is a consequence of natural selection, maximizing average net carbon gain over the leaf life cycle. Analyzing two large leaf trait datasets, we show that evergreen and deciduous species with diverse construction costs (assumed proportional to LMA) are selected by light, temperature, and growing-season length in different, but predictable, ways. We quantitatively explain the observed divergent latitudinal trends in evergreen and deciduous LMA and show how local distributions of LMA arise by selection under different environmental conditions acting on the species pool. These results illustrate how optimality principles can underpin a new theory for plant geography and terrestrial carbon dynamics.

No abstract

Homogalacturonan (HG) is the main component of pectins. HG methylesterification has recently emerged as a key determinant controlling cell attachment, organ formation, and phyllotaxy. However, whether and how HG methylesterification affects intercellular metabolite transport has rarely been reported. Here, we identified and characterized knockout mutants of the rice () gene encoding a putative pectin methyltransferase. mutants exhibit a remarkable decrease in the degree of methylesterification of HG in the culm-sieve element cell wall and a markedly reduced grain yield. The culm of mutant plants contains excessive sucrose (Suc), and aCO feeding experiment showed that the Suc overaccumulation in the culm was caused by blocked Suc translocation. These and other findings demonstrate that OsQUA2 is essential for maintaining a high degree of methylesterification of HG in the rice culm-sieve element cell wall, which may be critical for efficient Suc partitioning and grain filling. In addition, our results suggest that the apoplastic pathway is involved in long-distance Suc transport in rice. The identification and characterization of the gene and its functionality revealed a previously unknown contribution of HG methylesterification and provided insight into how modification of the cell wall regulates intercellular transport in plants.