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Development of leaf thickness for Plectranthus parviflorus – Influence of photosynthetically active radiation
Author(s) -
Nobel Park S.,
Hartsock Terry L.
Publication year - 1981
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1981.tb02692.x
Subject(s) - photosynthetically active radiation , photosynthesis , biology , botany , plectranthus , horticulture , zoology , lamiaceae
Photosynthetically active radiation (PhAR) is apparently the environmental factor having the greatest influence on leaf thickness for Plectranthus parviflorus Henckel (Labiatae). A four‐fold increase in leaf thickness from 280 to 1170 μm occurred as the PhAR was raised from 1.3 to 32.5 mol m −2 day −1 . Compared to a constant PhAR of 2.5 mol m −2 day −1 , a PhAR of 32.5 mol m −2 day −1 for one week during the first week (with return to 2.5 mol m −2 day −1 during the second and third weeks) led to an increase in final leaf thickness by 323 μm (to 802 μm). When increased PhAR was applied during the second week the increase in final thickness over the control was 217 μm, and when increased PhAR was applied during the third week it was 99 μm. However, leaf thickness was not simply responding to total daily PhAR, since a leaf 450 μm thick could occur at a low instantaneous PhAR for a long daytime (total daily PhAR of 1.5 mol m −2 day −1 ) and at a high PhAR for a short daytime (4.5 mol m −2 day −1 ). Total daily CO 2 uptake (net photosynthesis) was approximately the same in the two cases, suggesting that this is an important factor underlying the differences in leaf thickness. Leaf thickness is physiologically important, since thicker leaves tend to have greater mesophyll surface area per unit leaf area ( A mes / A ) and hence higher photosynthetic rates.