Effect of water and nitrogen supply on leaf growth and anatomy of tobacco burley.

The leaf growth and anatomy, together with the soil and plant water status of Burley tobacco, cultivated in open field, was monitored at 55 and 76 days after transplanting. Leaf dry matter was also considered. Three irrigation levels (40, 80 and 120% restitution of ET) were factorially combined with two levels of nitrogen fertilization (240 kg ha-1 and a control treatment not fertilized with nitrogen). The following thickness measurement were carried out on all samples: adaxial and abaxial epidermid, palisade tissue, spongy tissue and the whole leaf thickness. Moreover two diametric measurements of each cell designated as "A and B" were also taken. The AxB product was considered as cell dimension. The water volume influenced soil and plant water status, particularly leaf turgor pressure, while nitrogen fertilization did not affected plant water status. Leaf area, leaf thickness and cell size were linearly related to leaf turgor pressure. Leaf area, dry matter and leaf thickness increased with increasing water volume. Nitrogen fertilization positively influenced leaf area and negatively leaf thickness, the same trend was observed for tissues thicknesses, particularly for the spongy tissue. Water volume increased cell size, while nitrogen fertilization, on average, decreased cell size. This nitrogen effect was observed only with high water volumes, while with the lower irrigation volume (40% ET) cell size and tissue thickness increased with nitrogen availability (240 kg ha-1).